As a newbie to HVLP, I have encountered the following problem...
I am spraying Minwax (water-based) Polycrylic semi-gloss polyurethane.
Although the spray seems to atomize well, it seems that unless I put on
a fairly heavy coat that it deposits in discrete though very small
droplets resulting in a somewhat rough surface.
i.e. - the spray doesn't seem to coalesce into a uniform coat unless I
spray it on pretty thick. It's almost if some type of surface tension is
causing the spray to coalesce together rather than completely and
uniformly wetting the surface.
When I move the gun slower to let more finish deposit, I do get a
uniform sheen that completely 'wets' the surface (however this only
works when the surface is horizontal because otherwise it would run).
- Is this normal or am I doing something wrong?
- If so what are the likely causes and corrections?
Note: I am using the low cost but surprisingly well reviewed Harbor
Freight #66222 (purple) gun. My 8 gallon compressor seems to have enough
reserve to power the gun since it is able to cycle. on and off and the
pressure never drops below about 70psi.
The surface I am spraying is clean, well-sanded Birch plywood.
I have the inlet pressure set at about 30PSI.
I have made some (non-exhaustive) attempts to:
- Adjust the inlet pressure in the range of 20-40PSI
- Adjust the fluid volume
- Adjust the spray pattern (more round vs. more oval)
- Adjust the distance to the object (from maybe 8 to 16 inches)
- Adjust the speed at which I sweep across the object
While Minwax claims it hasn't tested and hence can't recommend
polycrylic for spraying, others have had good results with it. Also, it
seems to be of fairly high viscosity and hence seems to spray well.
Thanks
blueman <[email protected]> wrote:
> As a newbie to HVLP, I have encountered the following problem...
> I am spraying Minwax (water-based) Polycrylic semi-gloss polyurethane.
>
> Although the spray seems to atomize well, it seems that unless I put
> on
> a fairly heavy coat that it deposits in discrete though very small
> droplets resulting in a somewhat rough surface.
> i.e. - the spray doesn't seem to coalesce into a uniform coat unless I
> spray it on pretty thick. It's almost if some type of surface tension
> is
> causing the spray to coalesce together rather than completely and
> uniformly wetting the surface.
>
> When I move the gun slower to let more finish deposit, I do get a
> uniform sheen that completely 'wets' the surface (however this only
> works when the surface is horizontal because otherwise it would run).
>
> - Is this normal or am I doing something wrong?
> - If so what are the likely causes and corrections?
>
> Note: I am using the low cost but surprisingly well reviewed Harbor
> Freight #66222 (purple) gun. My 8 gallon compressor seems to have
> enough
> reserve to power the gun since it is able to cycle. on and off and the
> pressure never drops below about 70psi.
>
> The surface I am spraying is clean, well-sanded Birch plywood.
>
> I have the inlet pressure set at about 30PSI.
>
> I have made some (non-exhaustive) attempts to:
> - Adjust the inlet pressure in the range of 20-40PSI
> - Adjust the fluid volume
> - Adjust the spray pattern (more round vs. more oval)
> - Adjust the distance to the object (from maybe 8 to 16 inches)
> - Adjust the speed at which I sweep across the object
>
>
> While Minwax claims it hasn't tested and hence can't recommend
> polycrylic for spraying, others have had good results with it. Also,
> it
> seems to be of fairly high viscosity and hence seems to spray well.
>
> Thanks
I have had better luck spraying Fuhr water based products. I sprayed
polycrylic and it never leveled out as nicely as Fuhr.
Cm
blueman wrote:
> As a newbie to HVLP, I have encountered the following problem...
> I am spraying Minwax (water-based) Polycrylic semi-gloss polyurethane.
FYI, polycrylic is not polyurethane. It is acrylic and urethane is *MUCH*
harder and therefore scrarch resistant.
--
dadiOH
____________________________
dadiOH's dandies v3.06...
...a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico
"cm" <[email protected]> wrote in message
news:[email protected]...
> blueman <[email protected]> wrote:
>> As a newbie to HVLP, I have encountered the following problem...
>> I am spraying Minwax (water-based) Polycrylic semi-gloss polyurethane.
>>
>> Although the spray seems to atomize well, it seems that unless I put
>> on
>> a fairly heavy coat that it deposits in discrete though very small
>> droplets resulting in a somewhat rough surface.
>> i.e. - the spray doesn't seem to coalesce into a uniform coat unless I
>> spray it on pretty thick. It's almost if some type of surface tension
>> is
>> causing the spray to coalesce together rather than completely and
>> uniformly wetting the surface.
>>
>> When I move the gun slower to let more finish deposit, I do get a
>> uniform sheen that completely 'wets' the surface (however this only
>> works when the surface is horizontal because otherwise it would run).
>>
>> - Is this normal or am I doing something wrong?
>> - If so what are the likely causes and corrections?
>>
>> Note: I am using the low cost but surprisingly well reviewed Harbor
>> Freight #66222 (purple) gun. My 8 gallon compressor seems to have
>> enough
>> reserve to power the gun since it is able to cycle. on and off and the
>> pressure never drops below about 70psi.
>>
>> The surface I am spraying is clean, well-sanded Birch plywood.
>>
>> I have the inlet pressure set at about 30PSI.
>>
>> I have made some (non-exhaustive) attempts to:
>> - Adjust the inlet pressure in the range of 20-40PSI
>> - Adjust the fluid volume
>> - Adjust the spray pattern (more round vs. more oval)
>> - Adjust the distance to the object (from maybe 8 to 16 inches)
>> - Adjust the speed at which I sweep across the object
>>
>>
>> While Minwax claims it hasn't tested and hence can't recommend
>> polycrylic for spraying, others have had good results with it. Also,
>> it
>> seems to be of fairly high viscosity and hence seems to spray well.
>>
>> Thanks
> I have had better luck spraying Fuhr water based products. I sprayed
> polycrylic and it never leveled out as nicely as Fuhr.
>
> Cm
Especially if you're after that fuhrry look. :-)
Max
J. Clarke wrote:
> In article <[email protected]>,
> [email protected] says...
>>
>> blueman wrote:
>>> As a newbie to HVLP, I have encountered the following problem...
>>> I am spraying Minwax (water-based) Polycrylic semi-gloss
>>> polyurethane.
>>
>> FYI, polycrylic is not polyurethane. It is acrylic and urethane is
>> *MUCH* harder and therefore scratch resistant.
>
> Don't assume that harder means more scratch resistant.
Scratch resistance is one of the defining characteristics of hardness.
--
dadiOH
____________________________
dadiOH's dandies v3.06...
...a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico
J. Clarke wrote:
> In article <[email protected]>,
> [email protected] says...
>>
>> J. Clarke wrote:
>>> In article <[email protected]>,
>>> [email protected] says...
>>>>
>>>> blueman wrote:
>>>>> As a newbie to HVLP, I have encountered the following problem...
>>>>> I am spraying Minwax (water-based) Polycrylic semi-gloss
>>>>> polyurethane.
>>>>
>>>> FYI, polycrylic is not polyurethane. It is acrylic and urethane is
>>>> *MUCH* harder and therefore scratch resistant.
>>>
>>> Don't assume that harder means more scratch resistant.
>>
>>
>> Scratch resistance is one of the defining characteristics of
>> hardness.
>
> So tell us the engineering definition of "hardness" and quote your
> source.
Not being an engineer, I can't give you an engineering one, not sure it
would be pertinent anyway. However, a standard dictionary one is...
"Noun 1. hardness - the property of being rigid and resistant to
pressure; not easily scratched; measured on Mohs scale"
Mohs scale is used in determining the scratchability of minerals and varies
from talc on the low side to diamond at the high end. More about it...
http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness
Here's another (Rockwell hardness) that mentions scratching but the page is
most appropriate to metals...
http://www.calce.umd.edu/TSFA/Hardness_ad_.htm
More on Rockwell...
http://www.matweb.com/reference/rockwell-hardness.aspx
...but Rockwell isn't really appropriate as it measures resistance to
indentation. I guess if I happened to have a sclerometer in my pocket I
could test it myself. But I don't and I'm not about to go buy one to
satisfy your whimsical curiosity.
Here's one dealing with scratch resistance of wood finishes (no mention of
that relative to hardness though) see the last couple of lines in the
abstract. You can buy a full report if you want to.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T77-4XP8T5G-3&_user=10&_coverDate=03%2F31%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1558060347&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=db51d414ce0014533be98358a92d55f4&searchtype=a
And one more dealing with coatings on polycarbonate but certainly
pertinent...
"It is important to determine which test method is representative of the
application for the Polycarbonate sheet. If the sheet is likely to be
subject to continuous abrasion over an extended period of time, the Taber
Abrasion test may be appropriate. If the sheet is likely to be subject to
individual knocks and scratches, the Pencil Hardness test may be more
appropriate. Unfortunately, in many situations, neither test is totally
representative of the wear and tear that the sheet will experience in the
real world.
When selecting the coating for an application there is often a trade off
between the wear or scratch resistance and the processing properties of the
sheet. Typically as a coating becomes harder, it also becomes more brittle
and prone to cracking if bent. There are three broad groups of coating that
a user can consider:
Formable coatings - these coatings can easily be bent or formed without
cracking the coating. However, this formability is achieved by sacrificing
some of the abrasion resistance, as the coating is softer. While the
abrasion resistance is much better than uncoated Polycarbonate it is not
quite as good as the more traditional hard coatings.
Standard Hard Coats - these coatings tolerate a small amount of bending and
can easily be machined. They have good Taber Abrasion Resistance and pencil
hardness of 2H or 3H.
Super Hard Coats - these coatings generally crack if bent or machined, as
the coating is more brittle than standard hard-coats. Typically parts are
usually machined prior to coating. However, the anti-scratch coating
performance is excellent with pencil hardness values of 4H or even 5H."
http://highlinepc.blogspot.com/2009/11/selecting-abrasion-resistant-coatings.html
Finally, there is plain old common sense and/or empirical knowledge; both
dictate that soft things are scratched more easily than hard ones. YMMV but
I doubt it.
--
dadiOH
____________________________
dadiOH's dandies v3.06...
...a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico
Robatoy wrote:
> On Nov 27, 10:01 am, "dadiOH" <[email protected]> wrote:
>> J. Clarke wrote:
>>> In article <[email protected]>,
>>> [email protected] says...
>>
>>>> blueman wrote:
>>>>> As a newbie to HVLP, I have encountered the following problem...
>>>>> I am spraying Minwax (water-based) Polycrylic semi-gloss
>>>>> polyurethane.
>>
>>>> FYI, polycrylic is not polyurethane. It is acrylic and urethane is
>>>> *MUCH* harder and therefore scratch resistant.
>>
>>> Don't assume that harder means more scratch resistant.
>>
>> Scratch resistance is one of the defining characteristics of
>> hardness.
>>
>
> Not to get all 'clarke' about this, but tire rubber is, in terms of
> hardness. very soft but very scratch resistant.
Because it deforms. Resilient. Unless dipped in liquid nitrogen :)
--
dadiOH
____________________________
dadiOH's dandies v3.06...
...a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico
"Robatoy" <[email protected]> wrote in message
news:7b9b0193-a06f-4a1c-af6f-a21677ad0d8d@v19g2000yqa.googlegroups.com...
On Nov 27, 10:01 am, "dadiOH" <[email protected]> wrote:
> J. Clarke wrote:
> > In article <[email protected]>,
> > [email protected] says...
>
> >> blueman wrote:
> >>> As a newbie to HVLP, I have encountered the following problem...
> >>> I am spraying Minwax (water-based) Polycrylic semi-gloss
> >>> polyurethane.
>
> >> FYI, polycrylic is not polyurethane. It is acrylic and urethane is
> >> *MUCH* harder and therefore scratch resistant.
>
> > Don't assume that harder means more scratch resistant.
>
> Scratch resistance is one of the defining characteristics of hardness.
>
Not to get all 'clarke' about this, but tire rubber is, in terms of
hardness. very soft but very scratch resistant.
Hmm. I'll have to remember that the next time my wife scrubs a curb. {:-)
Max
On Nov 24, 10:25=A0pm, blueman <[email protected]> wrote:
> As a newbie to HVLP, I have encountered the following problem...
> I am spraying Minwax (water-based) Polycrylic semi-gloss polyurethane.
>
> Although the spray seems to atomize well, it seems that unless I put on
> a fairly heavy coat that it deposits in discrete though very small
> droplets resulting in a somewhat rough surface.
> i.e. - the spray doesn't seem to coalesce into a uniform coat unless I
> spray it on pretty thick. It's almost if some type of surface tension is
> causing the spray to coalesce together rather than completely and
> uniformly wetting the surface.
>
> When I move the gun slower to let more finish deposit, I do get a
> uniform sheen that completely 'wets' the surface (however this only
> works when the surface is horizontal because otherwise it would run).
>
> - Is this normal or am I doing something wrong?
> - If so what are the likely causes and corrections?
>
> Note: I am using the low cost but surprisingly well reviewed Harbor
> Freight #66222 (purple) gun. My 8 gallon compressor seems to have enough
> reserve to power the gun since it is able to cycle. on and off and the
> pressure never drops below about 70psi.
>
> The surface I am spraying is clean, well-sanded Birch plywood.
>
> I have the inlet pressure set at about 30PSI.
>
> I have made some (non-exhaustive) attempts to:
> - Adjust the inlet pressure in the range of 20-40PSI
> - Adjust the fluid volume
> - Adjust the spray pattern (more round vs. more oval)
> - Adjust the distance to the object (from maybe 8 to 16 inches)
> - Adjust the speed at which I sweep across the object
>
> While Minwax claims it hasn't tested and hence can't recommend
> polycrylic for spraying, others have had good results with it. Also, it
> seems to be of fairly high viscosity and hence seems to spray well.
>
> Thanks
I have sprayed the same product with a 2.0 tip on an HVLP gravity feed
gun at 45 psi inlet pressure. Medium fan.
It works a lot better in a cooler environment.
On Nov 25, 3:46=A0am, "[email protected]" <[email protected]>
wrote:
>
> FWIW, I think Rob may be on to something. =A0MOST guns (not all) that
> come with one tip use a 1.4 to 1.7 mm tip. =A0If you are in that range,
> it might not be large enough to spray your finish without thinning.
> If you didn't get another tip with the gun (the 2mm is intended for
> unthinned latex), try thinning your material about 10% with distilled
> water, then shooting it.
>
I bought that 2.0 gravity gun specifically for squirting Sikkens 3+1
primer. An automotive product that just works wonders on MDF's edges
and routed profiles. The build is insane, the sandability fantastic.
(For some reason my spellchecker balks at sandability...oh well.)
That stuff is so thick, it needs a tip that large. It's an Iwata
LPH440-201.
I took it, all nice and clean to my buddy's booth as I needed to blow
some thanes on a few sheets of luan. I checked the Polycryl with a
viscosity cup and looked almost too thin for the 2.0 (IMHO, a 1.8
would have done it too). I wasn't about to dirty up his pot-fed
equipment. (Waterbased snot in HIS guns? He would have murderized me.)
It went on so nice even though I was using a LOT of air to blow that
snot apart.
I have revisited the same spray schedule since with the same
results.... and if it works, don't mess with it.
On Nov 27, 1:16=A0pm, -MIKE- <[email protected]> wrote:
> On 11/27/10 11:50 AM, Robatoy wrote:
>
>
>
>
>
> > On Nov 27, 10:01 am, "dadiOH"<[email protected]> =A0wrote:
> >> J. Clarke wrote:
> >>> In article<[email protected]>,
> >>> [email protected] says...
>
> >>>> blueman wrote:
> >>>>> As a newbie to HVLP, I have encountered the following problem...
> >>>>> I am spraying Minwax (water-based) Polycrylic semi-gloss
> >>>>> polyurethane.
>
> >>>> FYI, polycrylic is not polyurethane. =A0It is acrylic and urethane i=
s
> >>>> *MUCH* harder and therefore scratch resistant.
>
> >>> Don't assume that harder means more scratch resistant.
>
> >> Scratch resistance is one of the defining characteristics of hardness.
>
> > Not to get all 'clarke' about this, but tire rubber is, in terms of
> > hardness. very soft but very scratch resistant.
>
> You succeeded, though. =A0 :-)
>
HEY!........ouch!
blueman wrote:
> "Mike Marlow" <[email protected]> writes:
>> blueman wrote:
>>
>>>
>>> Ahhh my HF gun comes with a 1.4 tip... and as I am just now learning
>>> that may make it come out to thin though I'm not sure I understand
>>> the mechanics of it. So perhaps that is part of the problem...
>>
>> Nope - the tip does not make it come out thinner - smaller tips
>> require thinner material. For a 1.4mm tip you would want quite a
>> thin material, or it will not spray it well. Start adding more
>> reducer (water for water bases materials) and test shoot until you
>> get a good pattern. Increment the amount of reducer by 10% or so
>> until you get t good, shootable mixture. Keep note of how much
>> reducer you are adding so that when you get to the point where it's
>> spraying well, you can reproduce that ratio of reducer to material
>> later on.
>
> Does one that get into a bit of a paradox:
> - Too thick means it doesn't atomize and coalesce properly
> - Too thin means it sprays nicely but runs and sages unless coat is
> applied thinly
I tried to correct this misunderstanding of yours in a past post. You are
too worried about how thick you are spraying it on. Don't be. Spray it on
like a layer of plastic you are stretching across the base material. If it
takes 3 coats - it takes 3 coats. If it takes 10 coats, it takes 10 coats.
Follow the manufacturer's directions for overcoats and just keep building it
up as necessary. The only thing you need to think about is imagining that
you are stretching a piece of plastic over the surface you are painting, and
making your spray application do that. If you are getting runs and sags
(and don't worry about that - I *still* shoot some once in a while), then
you're moving too slowly. Practice on scrap. Hear me? Practice on scrap.
>
> Which would seem to mean that if I use my current tip, but thin then I
> will have to put on more thinner coats.
Yup. You got it. No problem with doing it that way.
> While getting a wider tip would spare the need for adding reducer and
> would allow me to apply a relatively thicker coat without sagging or
> running.
And bring about other problems like shrinkage. There is no short cut to
doing it right. It sounds like you're looking for the one shot finish, and
that does not exist. Yes - a larger tip will put more down at once, but
then drying times extend, shrinkage enters into the picture, and if you do
run - you really run... or sag. It's more about technique than it is about
tip sizes. You really have to practice with that gun on scrap and get the
feel for it.
I just shot a bunch of primer through a detail gun. Would not lay on a
heavy build coat with the tip that I had. So... had to reduce the mixture
and shoot slower in order to get a good we coverage. Oh well. That's what
you do. If you are looking for the perfect tip for the perfect spray
material, on the perfect target - you're going to be very disappointed. Mix
up something your gun will shoot and.... practice.
>
> Am I understanding this tradeoff properly?
>
Yes, but my fear (and I may be reading you wrong...) is that you're looking
for a silver bullet. Spray painting is all about adapting to the situation.
Humidity, temperature, viscosity, and a lot of other factors, enter in on
every single spray job. That's why I'm so adamant about pushing your to
experiment, learn your gun, and practice. You can overcome any issue with
spraying if you understand your gun.
> Also, would having the right size tip and/or right viscosity typically
> allow me to lower the HVLP inlet pressure (I now have it cranked up to
> about 30psi but ideally, I know I could or should go a lot lower...).
Yes. The first thing you have to do is get the reduction such that your gun
can shoot it. So - reducing it to the point where you can get your pressure
down is very important. You don't really have HVLP anymore if you're
shooting at those high pressures. You're blasting more material into the
air than you realize. Might just as well grab a decent siphon gun and have
at it. So, once you get the reduction right - you know what I'm going to
say...
--
-Mike-
[email protected]
blueman wrote:
>
> Specifically, before I start shelling out loads of money for all
> possible sizes what 1 or 2 additional tips would give me a good range
> of coverage assuming I already have the 1.4?
>
I don't know what sizes are available for that gun, but anything in the
1.7-2.0mm range should be just fine. No need to buy more than one. You
really don't need a collection of them for "every conceivable" application.
--
-Mike-
[email protected]
blueman wrote:
> As a newbie to HVLP, I have encountered the following problem...
> I am spraying Minwax (water-based) Polycrylic semi-gloss polyurethane.
>
> Although the spray seems to atomize well, it seems that unless I put
> on a fairly heavy coat that it deposits in discrete though very small
> droplets resulting in a somewhat rough surface.
> i.e. - the spray doesn't seem to coalesce into a uniform coat unless I
> spray it on pretty thick. It's almost if some type of surface tension
> is causing the spray to coalesce together rather than completely and
> uniformly wetting the surface.
>
> When I move the gun slower to let more finish deposit, I do get a
> uniform sheen that completely 'wets' the surface (however this only
> works when the surface is horizontal because otherwise it would run).
I purchased the baby brother to that gun (46719) for detail work. Almost
all of my painting is with automotive refinishes, and I don't do much at all
with the stuff you're working with, but I'll share some comments and
experiences in general.
First off - don't assume that you'll get sags or runs on vertical surfaces.
If your gun is set up right, the material is the proper viscosity, and your
technique is right, you should easily be able to spray vertical or
horizontal surfaces with that gun. If you have to put on what you feel is a
heavy coat to get a wet coverage, then you probably need to either thin your
material or step up to a larger tip. As well - be careful with HVLP about
cranking your input pressure up too much. More is not better with a gun
like this. HVLP does not atomize like the old guns we were used to and it
really takes some experimenting to get used to your gun.
>
> - Is this normal or am I doing something wrong?
Of course - it's always the sprayer's fault - never the gun's fault...
> - If so what are the likely causes and corrections?
Generally - too high input air pressure, or too small a tip, or too thick a
mixture.
>
> Note: I am using the low cost but surprisingly well reviewed Harbor
> Freight #66222 (purple) gun. My 8 gallon compressor seems to have
> enough reserve to power the gun since it is able to cycle. on and off
> and the pressure never drops below about 70psi.
>
> The surface I am spraying is clean, well-sanded Birch plywood.
>
> I have the inlet pressure set at about 30PSI.
Try cranking that back - a good bit. Try 15-20 psi.
>
> I have made some (non-exhaustive) attempts to:
> - Adjust the inlet pressure in the range of 20-40PSI
Too high for most HVLP guns.
> - Adjust the fluid volume
Good adjustment - you'll be working with this adjustment a lot.
> - Adjust the spray pattern (more round vs. more oval)
Don't use this to get the right amount of material down. Use this to get
the right coverage pattern. If you have to needle the thing down to a small
pattern in order to get a decent coverage, you need to go back and look at
viscosity, tip size, and pressure.
> - Adjust the distance to the object (from maybe 8 to 16 inches)
16" is a mile away. Try moving in to 6-8"
> - Adjust the speed at which I sweep across the object
Always. Different materials will require different application speeds.
Thicker equals slower.
>
>
> While Minwax claims it hasn't tested and hence can't recommend
> polycrylic for spraying, others have had good results with it. Also,
> it seems to be of fairly high viscosity and hence seems to spray well.
>
Fairly high viscosity would not equate to spraying well. You might want to
add 25% more reducer than you've been using and observe the differences.
--
-Mike-
[email protected]
On Nov 27, 10:01=A0am, "dadiOH" <[email protected]> wrote:
> J. Clarke wrote:
> > In article <[email protected]>,
> > [email protected] says...
>
> >> blueman wrote:
> >>> As a newbie to HVLP, I have encountered the following problem...
> >>> I am spraying Minwax (water-based) Polycrylic semi-gloss
> >>> polyurethane.
>
> >> FYI, polycrylic is not polyurethane. =A0It is acrylic and urethane is
> >> *MUCH* harder and therefore scratch resistant.
>
> > Don't assume that harder means more scratch resistant.
>
> Scratch resistance is one of the defining characteristics of hardness.
>
Not to get all 'clarke' about this, but tire rubber is, in terms of
hardness. very soft but very scratch resistant.
To get a good, comprehensive answers to your questions, it would be
easier for you to simply search this group. The subject of HVLP
spraying of water borne materials has been discussed completely
several times.
Any time you have spraying errors you can have a *multitude* of
problems that will generate poor results. Some mimic others, so it is
best to get a list of common spraying problems and their diagnosis and
begin from there with your own equipment. I spent a lot of time
writing out the way to properly set up your gun for spraying a long
while back, and I was contacted by more than a few that thought the
info I put out was helpful. It might be to you as well.
FWIW, I think Rob may be on to something. MOST guns (not all) that
come with one tip use a 1.4 to 1.7 mm tip. If you are in that range,
it might not be large enough to spray your finish without thinning.
If you didn't get another tip with the gun (the 2mm is intended for
unthinned latex), try thinning your material about 10% with distilled
water, then shooting it.
I would also suggest that you find a good book(s) on spray technique.
There are a lot of good ones out there, and they can help you
troubleshoot your problems. Some of those books will help you
realize that there are too many variables to troubleshoot ACCURATELY
without a ton of info. They may also be able to help you figure out
what you are doing wrong as well.
Plan on investing some time and money in learning the spray process.
It is no different from any other part of learning a craft, but it
seems to be the biggest enemy of wood workers as they feel like it is
something that they can learn from osmosis. You can spray material
out of a gun by simply hooking it up. But to shoot a well laid,
consistent finish is something that takes time, practice, and above
all, patience.
Robert
In article <8a91b6cf-4e93-4e68-a62f-
[email protected]>, [email protected]
says...
>
> To get a good, comprehensive answers to your questions, it would be
> easier for you to simply search this group. The subject of HVLP
> spraying of water borne materials has been discussed completely
> several times.
>
> Any time you have spraying errors you can have a *multitude* of
> problems that will generate poor results. Some mimic others, so it is
> best to get a list of common spraying problems and their diagnosis and
> begin from there with your own equipment. I spent a lot of time
> writing out the way to properly set up your gun for spraying a long
> while back, and I was contacted by more than a few that thought the
> info I put out was helpful. It might be to you as well.
>
> FWIW, I think Rob may be on to something. MOST guns (not all) that
> come with one tip use a 1.4 to 1.7 mm tip. If you are in that range,
> it might not be large enough to spray your finish without thinning.
> If you didn't get another tip with the gun (the 2mm is intended for
> unthinned latex), try thinning your material about 10% with distilled
> water, then shooting it.
>
> I would also suggest that you find a good book(s) on spray technique.
> There are a lot of good ones out there, and they can help you
> troubleshoot your problems. Some of those books will help you
> realize that there are too many variables to troubleshoot ACCURATELY
> without a ton of info. They may also be able to help you figure out
> what you are doing wrong as well.
>
> Plan on investing some time and money in learning the spray process.
> It is no different from any other part of learning a craft, but it
> seems to be the biggest enemy of wood workers as they feel like it is
> something that they can learn from osmosis. You can spray material
> out of a gun by simply hooking it up. But to shoot a well laid,
> consistent finish is something that takes time, practice, and above
> all, patience.
Note that getting larger tips for the HF gun may be problematical--I
tried to get a larger one for mine and the gun had been discontinued as
had the tips. They may be available for the replacement model.
While the HF purple gun is fine _if_ out of the box it does what you
need, I've found that tcpglobal has what appears to be the same gun for
not a lot more money and they have a wide range of tips available, as
well as repair kits and accessories. Their tips work on _my_ HF purple
gun but mine isn't the current model.
Note--assume that the regulator that comes with the gun is dead, not
just with TCPglobal but HF as well--I've gotten one good one out of four
guns purchased.
If the tip is too small then you pretty much have to thin.
In article <[email protected]>,
[email protected] says...
>
> blueman wrote:
> > As a newbie to HVLP, I have encountered the following problem...
> > I am spraying Minwax (water-based) Polycrylic semi-gloss polyurethane.
>
> FYI, polycrylic is not polyurethane. It is acrylic and urethane is *MUCH*
> harder and therefore scrarch resistant.
Don't assume that harder means more scratch resistant. And polyurethane
coatings come in a wide range of hardnesses.
In article <[email protected]>,
[email protected] says...
>
> J. Clarke wrote:
> > In article <[email protected]>,
> > [email protected] says...
> >>
> >> blueman wrote:
> >>> As a newbie to HVLP, I have encountered the following problem...
> >>> I am spraying Minwax (water-based) Polycrylic semi-gloss
> >>> polyurethane.
> >>
> >> FYI, polycrylic is not polyurethane. It is acrylic and urethane is
> >> *MUCH* harder and therefore scratch resistant.
> >
> > Don't assume that harder means more scratch resistant.
>
>
> Scratch resistance is one of the defining characteristics of hardness.
So tell us the engineering definition of "hardness" and quote your
source.
In article <[email protected]>,
[email protected] says...
>
> J. Clarke wrote:
> > In article <[email protected]>,
> > [email protected] says...
> >>
> >> J. Clarke wrote:
> >>> In article <[email protected]>,
> >>> [email protected] says...
> >>>>
> >>>> blueman wrote:
> >>>>> As a newbie to HVLP, I have encountered the following problem...
> >>>>> I am spraying Minwax (water-based) Polycrylic semi-gloss
> >>>>> polyurethane.
> >>>>
> >>>> FYI, polycrylic is not polyurethane. It is acrylic and urethane is
> >>>> *MUCH* harder and therefore scratch resistant.
> >>>
> >>> Don't assume that harder means more scratch resistant.
> >>
> >>
> >> Scratch resistance is one of the defining characteristics of
> >> hardness.
> >
> > So tell us the engineering definition of "hardness" and quote your
> > source.
>
> Not being an engineer, I can't give you an engineering one, not sure it
> would be pertinent anyway. However, a standard dictionary one is...
> "Noun 1. hardness - the property of being rigid and resistant to
> pressure; not easily scratched; measured on Mohs scale"
>
> Mohs scale is used in determining the scratchability of minerals and varies
> from talc on the low side to diamond at the high end. More about it...
> http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness
Nice. Now, what "mineral" are we discussing?
> Here's another (Rockwell hardness) that mentions scratching but the page is
> most appropriate to metals...
> http://www.calce.umd.edu/TSFA/Hardness_ad_.htm
And that makes it clear that scratching is in the context of minerology.
> More on Rockwell...
> http://www.matweb.com/reference/rockwell-hardness.aspx
> ...but Rockwell isn't really appropriate as it measures resistance to
> indentation. I guess if I happened to have a sclerometer in my pocket I
> could test it myself. But I don't and I'm not about to go buy one to
> satisfy your whimsical curiosity.
And sclerometer is again a minerological tool. We aren't talking about
a rock here.
> Here's one dealing with scratch resistance of wood finishes (no mention of
> that relative to hardness though) see the last couple of lines in the
> abstract. You can buy a full report if you want to.
> http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T77-4XP8T5G-3&_user=10&_coverDate=03%2F31%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1558060347&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=db51d414ce0014533be98358a92d55f4&searchtype=a
>
> And one more dealing with coatings on polycarbonate but certainly
> pertinent...
> "It is important to determine which test method is representative of the
> application for the Polycarbonate sheet. If the sheet is likely to be
> subject to continuous abrasion over an extended period of time, the Taber
> Abrasion test may be appropriate. If the sheet is likely to be subject to
> individual knocks and scratches, the Pencil Hardness test may be more
> appropriate. Unfortunately, in many situations, neither test is totally
> representative of the wear and tear that the sheet will experience in the
> real world.
>
> When selecting the coating for an application there is often a trade off
> between the wear or scratch resistance and the processing properties of the
> sheet. Typically as a coating becomes harder, it also becomes more brittle
> and prone to cracking if bent. There are three broad groups of coating that
> a user can consider:
>
> Formable coatings - these coatings can easily be bent or formed without
> cracking the coating. However, this formability is achieved by sacrificing
> some of the abrasion resistance, as the coating is softer. While the
> abrasion resistance is much better than uncoated Polycarbonate it is not
> quite as good as the more traditional hard coatings.
>
> Standard Hard Coats - these coatings tolerate a small amount of bending and
> can easily be machined. They have good Taber Abrasion Resistance and pencil
> hardness of 2H or 3H.
>
> Super Hard Coats - these coatings generally crack if bent or machined, as
> the coating is more brittle than standard hard-coats. Typically parts are
> usually machined prior to coating. However, the anti-scratch coating
> performance is excellent with pencil hardness values of 4H or even 5H."
> http://highlinepc.blogspot.com/2009/11/selecting-abrasion-resistant-coatings.html
>
> Finally, there is plain old common sense and/or empirical knowledge; both
> dictate that soft things are scratched more easily than hard ones. YMMV but
> I doubt it.
In engineering, plain old common sense often leads you astray.
I once spent a good deal of my employer's money investigating this very
thing, and found out that the chemistry of the coating matters more than
the physical properties. We found that for a given hardness
polyurethane outperforms UHMW polyolefins, that two different brands of
urethane of the same hardness gave significantly different results, and
that the best durability under sandblasting was for a medium-hard
polyurethane (I forget the durometer--it was more than 20 years ago and
I didn't get to take the report home).
That particular coating is long since discontinued and it wouldn't be
any good for woodworking anyway--it bore a remarkable resemblance to
pigskin, in color, texture, and thickness, when cured.
In article <[email protected]>,
[email protected] says...
>
> "Robatoy" <[email protected]> wrote in message
> news:7b9b0193-a06f-4a1c-af6f-a21677ad0d8d@v19g2000yqa.googlegroups.com...
> On Nov 27, 10:01 am, "dadiOH" <[email protected]> wrote:
> > J. Clarke wrote:
> > > In article <[email protected]>,
> > > [email protected] says...
> >
> > >> blueman wrote:
> > >>> As a newbie to HVLP, I have encountered the following problem...
> > >>> I am spraying Minwax (water-based) Polycrylic semi-gloss
> > >>> polyurethane.
> >
> > >> FYI, polycrylic is not polyurethane. It is acrylic and urethane is
> > >> *MUCH* harder and therefore scratch resistant.
> >
> > > Don't assume that harder means more scratch resistant.
> >
> > Scratch resistance is one of the defining characteristics of hardness.
> >
>
> Not to get all 'clarke' about this, but tire rubber is, in terms of
> hardness. very soft but very scratch resistant.
>
>
>
> Hmm. I'll have to remember that the next time my wife scrubs a curb. {:-)
When she scrubs a curb hard enough to hit the wheel on it, see which
takes more damage.
>
> Max
On Nov 26, 5:15=A0pm, Larry Jaques <[email protected]>
wrote:
> On Fri, 26 Nov 2010 08:29:37 -0800 (PST), Robatoy
>
>
>
>
>
> <[email protected]> wrote:
> >On Nov 26, 10:28=A0am, "Max" <[email protected]> wrote:
> >> "cm" <[email protected]> wrote in message
>
> >>news:[email protected]...
>
> >> > blueman <[email protected]> wrote:
> >> >> As a newbie to HVLP, I have encountered the following problem...
> >> >> I am spraying Minwax (water-based) Polycrylic semi-gloss polyuretha=
ne.
>
> >> >> Although the spray seems to atomize well, it seems that unless I pu=
t
> >> >> on
> >> >> a fairly heavy coat that it deposits in discrete though very small
> >> >> droplets resulting in a somewhat rough surface.
> >> >> i.e. - the spray doesn't seem to coalesce into a uniform coat unles=
s I
> >> >> spray it on pretty thick. It's almost if some type of surface tensi=
on
> >> >> is
> >> >> causing the spray to coalesce together rather than completely and
> >> >> uniformly wetting the surface.
>
> >> >> When I move the gun slower to let more finish deposit, I do get a
> >> >> uniform sheen that completely 'wets' the surface (however this only
> >> >> works when the surface is horizontal because otherwise it would run=
).
>
> >> >> - Is this normal or am I doing something wrong?
> >> >> - If so what are the likely causes and corrections?
>
> >> >> Note: I am using the low cost but surprisingly well reviewed Harbor
> >> >> Freight #66222 (purple) gun. My 8 gallon compressor seems to have
> >> >> enough
> >> >> reserve to power the gun since it is able to cycle. on and off and =
the
> >> >> pressure never drops below about 70psi.
>
> >> >> The surface I am spraying is clean, well-sanded Birch plywood.
>
> >> >> I have the inlet pressure set at about 30PSI.
>
> >> >> I have made some (non-exhaustive) attempts to:
> >> >> - Adjust the inlet pressure in the range of 20-40PSI
> >> >> - Adjust the fluid volume
> >> >> - Adjust the spray pattern (more round vs. more oval)
> >> >> - Adjust the distance to the object (from maybe 8 to 16 inches)
> >> >> - Adjust the speed at which I sweep across the object
>
> >> >> While Minwax claims it hasn't tested and hence can't recommend
> >> >> polycrylic for spraying, others have had good results with it. Also=
,
> >> >> it
> >> >> seems to be of fairly high viscosity and hence seems to spray well.
>
> >> >> Thanks
> >> > I have had better luck spraying Fuhr water based products. I sprayed
> >> > polycrylic and it never leveled out as nicely as Fuhr.
>
> >> > Cm
>
> >> Especially if you're after that fuhrry look. =A0:-)
>
> >> Max
>
> >Ahw, fuhr crying out loud!!
>
> Poly-shades/crylic are a fuhr cry from decent finishes.
>
> --
> Education should provide the tools for a widening and deepening
> of life, for increased appreciation of all one sees or experiences.
> It should equip a person to live life well, to understand what is
> happening around him, for to live life well one must live life with
> awareness. =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0-- Louis L'Amour
Those finishes are targeted at lazy people who want quick 'n dirty.
They excel at that job. French polish? Nope.
On Sat, 27 Nov 2010 11:54:36 -0500, "J. Clarke" <[email protected]> wrote:
>In article <[email protected]>,
>[email protected] says...
>>
>> J. Clarke wrote:
>> > In article <[email protected]>,
>> > [email protected] says...
>> >>
>> >> blueman wrote:
>> >>> As a newbie to HVLP, I have encountered the following problem...
>> >>> I am spraying Minwax (water-based) Polycrylic semi-gloss
>> >>> polyurethane.
>> >>
>> >> FYI, polycrylic is not polyurethane. It is acrylic and urethane is
>> >> *MUCH* harder and therefore scratch resistant.
>> >
>> > Don't assume that harder means more scratch resistant.
>>
>>
>> Scratch resistance is one of the defining characteristics of hardness.
>
>So tell us the engineering definition of "hardness" and quote your
>source.
"The Mohs scale of mineral hardness characterizes the scratch resistance
of various minerals through the ability of a harder material to scratch
a softer material. It was created in 1812 by the German mineralogist
Friedrich Mohs and is one of several definitions of hardness in materials
science."
http://www.search.com/reference/Mohs_scale_of_mineral_hardness
>
blueman wrote:
>
> Ahhh my HF gun comes with a 1.4 tip... and as I am just now learning
> that may make it come out to thin though I'm not sure I understand the
> mechanics of it. So perhaps that is part of the problem...
Nope - the tip does not make it come out thinner - smaller tips require
thinner material. For a 1.4mm tip you would want quite a thin material, or
it will not spray it well. Start adding more reducer (water for water bases
materials) and test shoot until you get a good pattern. Increment the
amount of reducer by 10% or so until you get t good, shootable mixture.
Keep note of how much reducer you are adding so that when you get to the
point where it's spraying well, you can reproduce that ratio of reducer to
material later on.
--
-Mike-
[email protected]
On Wed, 24 Nov 2010 22:25:18 -0500, blueman <[email protected]> wrote:
>As a newbie to HVLP, I have encountered the following problem...
>I am spraying Minwax (water-based) Polycrylic semi-gloss polyurethane.
Condolences. Perhaps you could thin it with Floetrol. I believe that
Naily has sprayed that and will be piping up soon.
--
Experience is a good teacher, but she send in terrific bills.
-- Minna Thomas Antrim
On Nov 26, 10:28=A0am, "Max" <[email protected]> wrote:
> "cm" <[email protected]> wrote in message
>
> news:[email protected]...
>
>
>
>
>
> > blueman <[email protected]> wrote:
> >> As a newbie to HVLP, I have encountered the following problem...
> >> I am spraying Minwax (water-based) Polycrylic semi-gloss polyurethane.
>
> >> Although the spray seems to atomize well, it seems that unless I put
> >> on
> >> a fairly heavy coat that it deposits in discrete though very small
> >> droplets resulting in a somewhat rough surface.
> >> i.e. - the spray doesn't seem to coalesce into a uniform coat unless I
> >> spray it on pretty thick. It's almost if some type of surface tension
> >> is
> >> causing the spray to coalesce together rather than completely and
> >> uniformly wetting the surface.
>
> >> When I move the gun slower to let more finish deposit, I do get a
> >> uniform sheen that completely 'wets' the surface (however this only
> >> works when the surface is horizontal because otherwise it would run).
>
> >> - Is this normal or am I doing something wrong?
> >> - If so what are the likely causes and corrections?
>
> >> Note: I am using the low cost but surprisingly well reviewed Harbor
> >> Freight #66222 (purple) gun. My 8 gallon compressor seems to have
> >> enough
> >> reserve to power the gun since it is able to cycle. on and off and the
> >> pressure never drops below about 70psi.
>
> >> The surface I am spraying is clean, well-sanded Birch plywood.
>
> >> I have the inlet pressure set at about 30PSI.
>
> >> I have made some (non-exhaustive) attempts to:
> >> - Adjust the inlet pressure in the range of 20-40PSI
> >> - Adjust the fluid volume
> >> - Adjust the spray pattern (more round vs. more oval)
> >> - Adjust the distance to the object (from maybe 8 to 16 inches)
> >> - Adjust the speed at which I sweep across the object
>
> >> While Minwax claims it hasn't tested and hence can't recommend
> >> polycrylic for spraying, others have had good results with it. Also,
> >> it
> >> seems to be of fairly high viscosity and hence seems to spray well.
>
> >> Thanks
> > I have had better luck spraying Fuhr water based products. I sprayed
> > polycrylic and it never leveled out as nicely as Fuhr.
>
> > Cm
>
> Especially if you're after that fuhrry look. =A0:-)
>
> Max
Ahw, fuhr crying out loud!!
On 11/27/10 11:50 AM, Robatoy wrote:
> On Nov 27, 10:01 am, "dadiOH"<[email protected]> wrote:
>> J. Clarke wrote:
>>> In article<[email protected]>,
>>> [email protected] says...
>>
>>>> blueman wrote:
>>>>> As a newbie to HVLP, I have encountered the following problem...
>>>>> I am spraying Minwax (water-based) Polycrylic semi-gloss
>>>>> polyurethane.
>>
>>>> FYI, polycrylic is not polyurethane. It is acrylic and urethane is
>>>> *MUCH* harder and therefore scratch resistant.
>>
>>> Don't assume that harder means more scratch resistant.
>>
>> Scratch resistance is one of the defining characteristics of hardness.
>>
>
> Not to get all 'clarke' about this, but tire rubber is, in terms of
> hardness. very soft but very scratch resistant.
>
You succeeded, though. :-)
"one of" not "the"
--
-MIKE-
"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com
[email protected]
---remove "DOT" ^^^^ to reply
On 11/27/10 12:22 PM, Robatoy wrote:
> On Nov 27, 1:16 pm, -MIKE-<[email protected]> wrote:
>> On 11/27/10 11:50 AM, Robatoy wrote:
>>
>>
>>
>>
>>
>>> On Nov 27, 10:01 am, "dadiOH"<[email protected]> wrote:
>>>> J. Clarke wrote:
>>>>> In article<[email protected]>,
>>>>> [email protected] says...
>>
>>>>>> blueman wrote:
>>>>>>> As a newbie to HVLP, I have encountered the following problem...
>>>>>>> I am spraying Minwax (water-based) Polycrylic semi-gloss
>>>>>>> polyurethane.
>>
>>>>>> FYI, polycrylic is not polyurethane. It is acrylic and urethane is
>>>>>> *MUCH* harder and therefore scratch resistant.
>>
>>>>> Don't assume that harder means more scratch resistant.
>>
>>>> Scratch resistance is one of the defining characteristics of hardness.
>>
>>> Not to get all 'clarke' about this, but tire rubber is, in terms of
>>> hardness. very soft but very scratch resistant.
>>
>> You succeeded, though. :-)
>>
> HEY!........ouch!
>
Happy Thanksgiving! :-p
--
-MIKE-
"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com
[email protected]
---remove "DOT" ^^^^ to reply
On Fri, 26 Nov 2010 08:29:37 -0800 (PST), Robatoy
<[email protected]> wrote:
>On Nov 26, 10:28 am, "Max" <[email protected]> wrote:
>> "cm" <[email protected]> wrote in message
>>
>> news:[email protected]...
>>
>>
>>
>>
>>
>> > blueman <[email protected]> wrote:
>> >> As a newbie to HVLP, I have encountered the following problem...
>> >> I am spraying Minwax (water-based) Polycrylic semi-gloss polyurethane.
>>
>> >> Although the spray seems to atomize well, it seems that unless I put
>> >> on
>> >> a fairly heavy coat that it deposits in discrete though very small
>> >> droplets resulting in a somewhat rough surface.
>> >> i.e. - the spray doesn't seem to coalesce into a uniform coat unless I
>> >> spray it on pretty thick. It's almost if some type of surface tension
>> >> is
>> >> causing the spray to coalesce together rather than completely and
>> >> uniformly wetting the surface.
>>
>> >> When I move the gun slower to let more finish deposit, I do get a
>> >> uniform sheen that completely 'wets' the surface (however this only
>> >> works when the surface is horizontal because otherwise it would run).
>>
>> >> - Is this normal or am I doing something wrong?
>> >> - If so what are the likely causes and corrections?
>>
>> >> Note: I am using the low cost but surprisingly well reviewed Harbor
>> >> Freight #66222 (purple) gun. My 8 gallon compressor seems to have
>> >> enough
>> >> reserve to power the gun since it is able to cycle. on and off and the
>> >> pressure never drops below about 70psi.
>>
>> >> The surface I am spraying is clean, well-sanded Birch plywood.
>>
>> >> I have the inlet pressure set at about 30PSI.
>>
>> >> I have made some (non-exhaustive) attempts to:
>> >> - Adjust the inlet pressure in the range of 20-40PSI
>> >> - Adjust the fluid volume
>> >> - Adjust the spray pattern (more round vs. more oval)
>> >> - Adjust the distance to the object (from maybe 8 to 16 inches)
>> >> - Adjust the speed at which I sweep across the object
>>
>> >> While Minwax claims it hasn't tested and hence can't recommend
>> >> polycrylic for spraying, others have had good results with it. Also,
>> >> it
>> >> seems to be of fairly high viscosity and hence seems to spray well.
>>
>> >> Thanks
>> > I have had better luck spraying Fuhr water based products. I sprayed
>> > polycrylic and it never leveled out as nicely as Fuhr.
>>
>> > Cm
>>
>> Especially if you're after that fuhrry look. :-)
>>
>> Max
>
>Ahw, fuhr crying out loud!!
Poly-shades/crylic are a fuhr cry from decent finishes.
--
Education should provide the tools for a widening and deepening
of life, for increased appreciation of all one sees or experiences.
It should equip a person to live life well, to understand what is
happening around him, for to live life well one must live life with
awareness. -- Louis L'Amour
"Mike Marlow" <[email protected]> writes:
> blueman wrote:
>
>>
>> Ahhh my HF gun comes with a 1.4 tip... and as I am just now learning
>> that may make it come out to thin though I'm not sure I understand the
>> mechanics of it. So perhaps that is part of the problem...
>
> Nope - the tip does not make it come out thinner - smaller tips require
> thinner material. For a 1.4mm tip you would want quite a thin material, or
> it will not spray it well. Start adding more reducer (water for water bases
> materials) and test shoot until you get a good pattern. Increment the
> amount of reducer by 10% or so until you get t good, shootable mixture.
> Keep note of how much reducer you are adding so that when you get to the
> point where it's spraying well, you can reproduce that ratio of reducer to
> material later on.
Does one that get into a bit of a paradox:
- Too thick means it doesn't atomize and coalesce properly
- Too thin means it sprays nicely but runs and sages unless coat is
applied thinly
Which would seem to mean that if I use my current tip, but thin then I
will have to put on more thinner coats.
While getting a wider tip would spare the need for adding reducer and
would allow me to apply a relatively thicker coat without sagging or
running.
Am I understanding this tradeoff properly?
Also, would having the right size tip and/or right viscosity typically
allow me to lower the HVLP inlet pressure (I now have it cranked up to
about 30psi but ideally, I know I could or should go a lot lower...).
Robatoy <[email protected]> writes:
> On Nov 25, 3:46Â am, "[email protected]" <[email protected]>
> wrote:
>
>>
>> FWIW, I think Rob may be on to something. Â MOST guns (not all) that
>> come with one tip use a 1.4 to 1.7 mm tip. Â If you are in that range,
>> it might not be large enough to spray your finish without thinning.
>> If you didn't get another tip with the gun (the 2mm is intended for
>> unthinned latex), try thinning your material about 10% with distilled
>> water, then shooting it.
>>
>
> I bought that 2.0 gravity gun specifically for squirting Sikkens 3+1
> primer. An automotive product that just works wonders on MDF's edges
> and routed profiles. The build is insane, the sandability fantastic.
> (For some reason my spellchecker balks at sandability...oh well.)
> That stuff is so thick, it needs a tip that large. It's an Iwata
> LPH440-201.
> I took it, all nice and clean to my buddy's booth as I needed to blow
> some thanes on a few sheets of luan. I checked the Polycryl with a
> viscosity cup and looked almost too thin for the 2.0 (IMHO, a 1.8
> would have done it too). I wasn't about to dirty up his pot-fed
> equipment. (Waterbased snot in HIS guns? He would have murderized me.)
> It went on so nice even though I was using a LOT of air to blow that
> snot apart.
>
> I have revisited the same spray schedule since with the same
> results.... and if it works, don't mess with it.
OK - now that I am pretty convinced that I need more than my stock 1.4
tip, as a newbie and a hobbyist, what would be the most useful other
tips to order assuming I might want to spray latex paint, lacquer,
shellac, oil-based poly, primer (for wood)?
Specifically, before I start shelling out loads of money for all
possible sizes what 1 or 2 additional tips would give me a good range of
coverage assuming I already have the 1.4?
Thanks
"Mike Marlow" <[email protected]> writes:
> blueman wrote:
>
>>
>> Specifically, before I start shelling out loads of money for all
>> possible sizes what 1 or 2 additional tips would give me a good range
>> of coverage assuming I already have the 1.4?
>>
>
> I don't know what sizes are available for that gun, but anything in the
> 1.7-2.0mm range should be just fine. No need to buy more than one. You
> really don't need a collection of them for "every conceivable" application.
Not to be too anal... but if in the future I hope to also shoot
semi-gloss Benjamin Moore Latex, would I be better off getting a 1.8 or
a 2.0 (or is the difference really too small to worry about...)
Robatoy <[email protected]> writes:
> On Nov 25, 3:46Â am, "[email protected]" <[email protected]>
> wrote:
>
>>
>> FWIW, I think Rob may be on to something. Â MOST guns (not all) that
>> come with one tip use a 1.4 to 1.7 mm tip. Â If you are in that range,
>> it might not be large enough to spray your finish without thinning.
>> If you didn't get another tip with the gun (the 2mm is intended for
>> unthinned latex), try thinning your material about 10% with distilled
>> water, then shooting it.
>>
>
> I bought that 2.0 gravity gun specifically for squirting Sikkens 3+1
> primer. An automotive product that just works wonders on MDF's edges
> and routed profiles. The build is insane, the sandability fantastic.
> (For some reason my spellchecker balks at sandability...oh well.)
> That stuff is so thick, it needs a tip that large. It's an Iwata
> LPH440-201.
> I took it, all nice and clean to my buddy's booth as I needed to blow
> some thanes on a few sheets of luan. I checked the Polycryl with a
> viscosity cup and looked almost too thin for the 2.0 (IMHO, a 1.8
> would have done it too). I wasn't about to dirty up his pot-fed
> equipment. (Waterbased snot in HIS guns? He would have murderized me.)
> It went on so nice even though I was using a LOT of air to blow that
> snot apart.
>
> I have revisited the same spray schedule since with the same
> results.... and if it works, don't mess with it.
I think you have diagnosed it spot on. I didn't (and still don't fully)
understand how tip size works but you have pointed me in the right
direction.
I think the problem is finding other than non-stock 1.4 tip sizes for
this gun, though I have seen at least two alternative suggestions:
1. Buy a spare 1.4 tip and drill out the hole a little
2. Find a tip from other companies that fits...
Thanks for the pointers and experience!
"J. Clarke" <[email protected]> writes:
> In article <8a91b6cf-4e93-4e68-a62f-
> [email protected]>, [email protected]
> says...
>>
>> To get a good, comprehensive answers to your questions, it would be
>> easier for you to simply search this group. The subject of HVLP
>> spraying of water borne materials has been discussed completely
>> several times.
>>
>> Any time you have spraying errors you can have a *multitude* of
>> problems that will generate poor results. Some mimic others, so it is
>> best to get a list of common spraying problems and their diagnosis and
>> begin from there with your own equipment. I spent a lot of time
>> writing out the way to properly set up your gun for spraying a long
>> while back, and I was contacted by more than a few that thought the
>> info I put out was helpful. It might be to you as well.
>>
>> FWIW, I think Rob may be on to something. MOST guns (not all) that
>> come with one tip use a 1.4 to 1.7 mm tip. If you are in that range,
>> it might not be large enough to spray your finish without thinning.
>> If you didn't get another tip with the gun (the 2mm is intended for
>> unthinned latex), try thinning your material about 10% with distilled
>> water, then shooting it.
>>
>> I would also suggest that you find a good book(s) on spray technique.
>> There are a lot of good ones out there, and they can help you
>> troubleshoot your problems. Some of those books will help you
>> realize that there are too many variables to troubleshoot ACCURATELY
>> without a ton of info. They may also be able to help you figure out
>> what you are doing wrong as well.
>>
>> Plan on investing some time and money in learning the spray process.
>> It is no different from any other part of learning a craft, but it
>> seems to be the biggest enemy of wood workers as they feel like it is
>> something that they can learn from osmosis. You can spray material
>> out of a gun by simply hooking it up. But to shoot a well laid,
>> consistent finish is something that takes time, practice, and above
>> all, patience.
>
> Note that getting larger tips for the HF gun may be problematical--I
> tried to get a larger one for mine and the gun had been discontinued as
> had the tips. They may be available for the replacement model.
>
> While the HF purple gun is fine _if_ out of the box it does what you
> need, I've found that tcpglobal has what appears to be the same gun for
> not a lot more money and they have a wide range of tips available, as
> well as repair kits and accessories. Their tips work on _my_ HF purple
> gun but mine isn't the current model.
- Do you know what model you have?
- What would I have to check to determine compatibility?
(beyond thread diameter and pitch)
>
> Note--assume that the regulator that comes with the gun is dead, not
> just with TCPglobal but HF as well--I've gotten one good one out of four
> guns purchased.
Well the regulator "seems" to work in that at least I can dial up
different pressures... Were yours *totally* broken or just inaccurate?
(i.e. did you have to check against a pressure gauge to determine
whether or not it was working or could you just tell by the dial)
> If the tip is too small then you pretty much have to thin.
Ahhh well I have the stock 1.4 tip so perhaps that is the problem...
Robatoy <[email protected]> writes:
> On Nov 24, 10:25Â pm, blueman <[email protected]> wrote:
>> As a newbie to HVLP, I have encountered the following problem...
>> I am spraying Minwax (water-based) Polycrylic semi-gloss polyurethane.
>>
>> Although the spray seems to atomize well, it seems that unless I put on
>> a fairly heavy coat that it deposits in discrete though very small
>> droplets resulting in a somewhat rough surface.
>> i.e. - the spray doesn't seem to coalesce into a uniform coat unless I
>> spray it on pretty thick. It's almost if some type of surface tension is
>> causing the spray to coalesce together rather than completely and
>> uniformly wetting the surface.
>>
>> When I move the gun slower to let more finish deposit, I do get a
>> uniform sheen that completely 'wets' the surface (however this only
>> works when the surface is horizontal because otherwise it would run).
>>
>> - Is this normal or am I doing something wrong?
>> - If so what are the likely causes and corrections?
>>
>> Note: I am using the low cost but surprisingly well reviewed Harbor
>> Freight #66222 (purple) gun. My 8 gallon compressor seems to have enough
>> reserve to power the gun since it is able to cycle. on and off and the
>> pressure never drops below about 70psi.
>>
>> The surface I am spraying is clean, well-sanded Birch plywood.
>>
>> I have the inlet pressure set at about 30PSI.
>>
>> I have made some (non-exhaustive) attempts to:
>> - Adjust the inlet pressure in the range of 20-40PSI
>> - Adjust the fluid volume
>> - Adjust the spray pattern (more round vs. more oval)
>> - Adjust the distance to the object (from maybe 8 to 16 inches)
>> - Adjust the speed at which I sweep across the object
>>
>> While Minwax claims it hasn't tested and hence can't recommend
>> polycrylic for spraying, others have had good results with it. Also, it
>> seems to be of fairly high viscosity and hence seems to spray well.
>>
>> Thanks
>
> I have sprayed the same product with a 2.0 tip on an HVLP gravity feed
> gun at 45 psi inlet pressure. Medium fan.
> It works a lot better in a cooler environment.
Ahhh my HF gun comes with a 1.4 tip... and as I am just now learning
that may make it come out to thin though I'm not sure I understand the
mechanics of it. So perhaps that is part of the problem...
On Sat, 27 Nov 2010 15:44:17 -0500, "J. Clarke" <[email protected]> wrote:
>In article <[email protected]>,
>[email protected] says...
>>
>> J. Clarke wrote:
>> > In article <[email protected]>,
>> > [email protected] says...
>> >>
>> >> J. Clarke wrote:
>> >>> In article <[email protected]>,
>> >>> [email protected] says...
>> >>>>
>> >>>> blueman wrote:
>> >>>>> As a newbie to HVLP, I have encountered the following problem...
>> >>>>> I am spraying Minwax (water-based) Polycrylic semi-gloss
>> >>>>> polyurethane.
>> >>>>
>> >>>> FYI, polycrylic is not polyurethane. It is acrylic and urethane is
>> >>>> *MUCH* harder and therefore scratch resistant.
>> >>>
>> >>> Don't assume that harder means more scratch resistant.
>> >>
>> >>
>> >> Scratch resistance is one of the defining characteristics of
>> >> hardness.
>> >
>> > So tell us the engineering definition of "hardness" and quote your
>> > source.
>>
>> Not being an engineer, I can't give you an engineering one, not sure it
>> would be pertinent anyway. However, a standard dictionary one is...
>> "Noun 1. hardness - the property of being rigid and resistant to
>> pressure; not easily scratched; measured on Mohs scale"
>>
>> Mohs scale is used in determining the scratchability of minerals and varies
>> from talc on the low side to diamond at the high end. More about it...
>> http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness
>
>Nice. Now, what "mineral" are we discussing?
Oh glass, wood, pretty much any material in use today.
>> Here's another (Rockwell hardness) that mentions scratching but the page is
>> most appropriate to metals...
>> http://www.calce.umd.edu/TSFA/Hardness_ad_.htm
>
>And that makes it clear that scratching is in the context of minerology.
...and other uses. It *is* one of the scientific meanings/measures of
hardness.
>> More on Rockwell...
>> http://www.matweb.com/reference/rockwell-hardness.aspx
>> ...but Rockwell isn't really appropriate as it measures resistance to
>> indentation. I guess if I happened to have a sclerometer in my pocket I
>> could test it myself. But I don't and I'm not about to go buy one to
>> satisfy your whimsical curiosity.
>
>And sclerometer is again a minerological tool. We aren't talking about
>a rock here.
>
>> Here's one dealing with scratch resistance of wood finishes (no mention of
>> that relative to hardness though) see the last couple of lines in the
>> abstract. You can buy a full report if you want to.
>> http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T77-4XP8T5G-3&_user=10&_coverDate=03%2F31%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1558060347&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=db51d414ce0014533be98358a92d55f4&searchtype=a
>>
>> And one more dealing with coatings on polycarbonate but certainly
>> pertinent...
>> "It is important to determine which test method is representative of the
>> application for the Polycarbonate sheet. If the sheet is likely to be
>> subject to continuous abrasion over an extended period of time, the Taber
>> Abrasion test may be appropriate. If the sheet is likely to be subject to
>> individual knocks and scratches, the Pencil Hardness test may be more
>> appropriate. Unfortunately, in many situations, neither test is totally
>> representative of the wear and tear that the sheet will experience in the
>> real world.
>>
>> When selecting the coating for an application there is often a trade off
>> between the wear or scratch resistance and the processing properties of the
>> sheet. Typically as a coating becomes harder, it also becomes more brittle
>> and prone to cracking if bent. There are three broad groups of coating that
>> a user can consider:
>>
>> Formable coatings - these coatings can easily be bent or formed without
>> cracking the coating. However, this formability is achieved by sacrificing
>> some of the abrasion resistance, as the coating is softer. While the
>> abrasion resistance is much better than uncoated Polycarbonate it is not
>> quite as good as the more traditional hard coatings.
>>
>> Standard Hard Coats - these coatings tolerate a small amount of bending and
>> can easily be machined. They have good Taber Abrasion Resistance and pencil
>> hardness of 2H or 3H.
>>
>> Super Hard Coats - these coatings generally crack if bent or machined, as
>> the coating is more brittle than standard hard-coats. Typically parts are
>> usually machined prior to coating. However, the anti-scratch coating
>> performance is excellent with pencil hardness values of 4H or even 5H."
>> http://highlinepc.blogspot.com/2009/11/selecting-abrasion-resistant-coatings.html
>>
>> Finally, there is plain old common sense and/or empirical knowledge; both
>> dictate that soft things are scratched more easily than hard ones. YMMV but
>> I doubt it.
>
>In engineering, plain old common sense often leads you astray.
>
>I once spent a good deal of my employer's money investigating this very
>thing, and found out that the chemistry of the coating matters more than
>the physical properties. We found that for a given hardness
>polyurethane outperforms UHMW polyolefins, that two different brands of
>urethane of the same hardness gave significantly different results, and
>that the best durability under sandblasting was for a medium-hard
>polyurethane (I forget the durometer--it was more than 20 years ago and
>I didn't get to take the report home).
>
>That particular coating is long since discontinued and it wouldn't be
>any good for woodworking anyway--it bore a remarkable resemblance to
>pigskin, in color, texture, and thickness, when cured.
>