Grit of sandpaper to use between coats of poly?

On Sun, 16 Oct 2011 21:08:03 -0700 (PDT), Father Haskell
<[email protected]> wrote:


nother) coat.
>>
>> I used the same 600 grit on the large surface area, using a block with a piece of scotch-brite in-between the block and the paper to "soften" the block. I don't know if this made any sense at all, but it didn't seem to hurt anything. This surface did not start out as smooth as the oak border, and the sanding did give it the slightest "white" cast (dust) when viewed at the right angle against the light.  
>>
>> I'm wondering if using the 600 paper is likely to bite me in the ass in any way later. Does the next coat of poly need more roughness to adhere? Am I giving up the chance to more thoroughly smooth the main area?
>
>220 between coats is fine enough and gets the job done
>fast. If you want a gloss finish, use lacquer or shellac.
>Either one is harder than poly and rubs out better.


If you use 220 between coats, put on four coats, then let it cure for
a few weeks. Now you can polish it out with 320, 600 wet,
rottenstone, pumice, and finally, a coat of wax. It will give a
really nice professional looking finish.

Greg Guarino wrote:

>
> I'm wondering if using the 600 paper is likely to bite me in the ass
> in any way later. Does the next coat of poly need more roughness to
> adhere? Am I giving up the chance to more thoroughly smooth the main
> area?

The 600 won't cause you any problems with tooth on additional coats.
Generally speaking, the lighter the sandpaper you can get away with, to
knock down dust nibs, etc., the better. If you find that you need, or want
to use 400 on other areas - just because it's faster, then just take it up
to 600 when you're done so that any swirls or sanding marks are all the
same. For grins and giggles - get yourself some automotive rubbing
compound, and hit your pieces with it after the 600. Get at least a medium
cut and not a glazing compound. You'll really like what you see and feel...

--

-Mike-
[email protected]

On 10/16/2011 8:51 PM, Greg Guarino wrote:
. It looks and feels quite nice, even though I plan to add at least one
more (and likely another) coat.
>
> I used the same 600 grit on the large surface area, using a block with a piece of scotch-brite in-between the block and the paper to "soften" the block. I don't know if this made any sense at all, but it didn't seem to hurt anything. This surface did not start out as smooth as the oak border, and the sanding did give it the slightest "white" cast (dust) when viewed at the right angle against the light.
>
> I'm wondering if using the 600 paper is likely to bite me in the ass in any way later. Does the next coat of poly need more roughness to adhere? Am I giving up the chance to more thoroughly smooth the main area?

If you switch to a gel varnish you no longer need to do any
sanding/scuffing between coats and you end up with a smooth satin finish.

On Oct 17, 5:58=A0am, Ed Pawlowski <[email protected]> wrote:
> On Sun, 16 Oct 2011 21:08:03 -0700 (PDT), Father Haskell
>
> <[email protected]> wrote:
>
> nother) coat.
>
>
>
> >> I used the same 600 grit on the large surface area, using a block with=
a piece of scotch-brite in-between the block and the paper to "soften" the=
block. I don't know if this made any sense at all, but it didn't seem to h=
urt anything. This surface did not start out as smooth as the oak border, a=
nd the sanding did give it the slightest "white" cast (dust) when viewed at=
the right angle against the light. =A0
>
> >> I'm wondering if using the 600 paper is likely to bite me in the ass i=
n any way later. Does the next coat of poly need more roughness to adhere? =
Am I giving up the chance to more thoroughly smooth the main area?
>
> >220 between coats is fine enough and gets the job done
> >fast. =A0If you want a gloss finish, use lacquer or shellac.
> >Either one is harder than poly and rubs out better.
>
> If you use 220 between coats, put on four coats, then let it cure for
> a few weeks. =A0Now you can polish it out with 320, 600 wet,
> rottenstone, pumice, and finally, a coat of wax. =A0It will give a
> really nice professional looking finish.

Your work will pay off a lot more with lacquer or shellac.
They're not "difficult" to apply if you lay them on fast
and thin -- trying to fill in skips before the coat is
dry is what causes ridges. Actually, they're a
bit less work than poly, since you don't have to
sand between coats.

On Oct 16, 9:51=A0pm, Greg Guarino <[email protected]> wrote:
> Finishing the desktop I've mentioned elsewhere. I'm using very pedestrian=
stuff: MinWax Poly.
>
> I made a test piece using the three types of wood that make up the deskto=
p. For the test piece, I sanded to 220, wiped with mineral spirits, and app=
lied Semi Gloss poly. I then put on two coats of Satin Poly, lightly machin=
e sanding with 220 in-between. I liked the results, except for some run mar=
ks that probably resulted from too thick a coat plus hanging the test piece=
vertically.
>
> Why two different glosses? A friend of mine did something similar on some=
flooring with good results, plus I had some semi laying around. I don't kn=
ow if using semi for the first coat had any practical effect, but I decided=
it couldn't hurt. =A0
>
> I've now got two coats on the actual project. Not content to leave well e=
nough alone, I varied the procedure just a little bit. I again sanded to 22=
0 and applied semi gloss first. That was Saturday. I had a (music) gig Sund=
ay afternoon, so I got up early to see if I could get in another coat. Our =
house is attached, and thought the power tools at 7:30 in the morning might=
not be appreciated next door, so I decided to try hand-sanding at least th=
e edges.
>
> I used 400 grit, which I had never tried before. As the edges are rounded=
, I used it without a block, just with fingers. =A0 It gave the edges (oak)=
a lovely smooth feel. I decided to do the whole surface with the 400, usin=
g a block for the large area. I then applied another coat of satin.
>
> I took a look at the result after my gig. It's coming along. I decided no=
t to take on putting on another coat tonight, but I couldn't resist sanding=
it a tad, to see what the feel would be like.
>
> So here we're coming to the question, finally. I again used a small piece=
of sandpaper in my fingers for the edges, but decided to try 600 grit. I f=
igured if it didn't adequately knock down the small amount of roughness tha=
t remained, I could go beck to the 400.
>
> I was surprised by the result. It smoothed the surface nicely, but didn't=
appreciably dull it. It looks and feels quite nice, even though I plan to =
add at least one more (and likely another) coat.
>
> I used the same 600 grit on the large surface area, using a block with a =
piece of scotch-brite in-between the block and the paper to "soften" the bl=
ock. I don't know if this made any sense at all, but it didn't seem to hurt=
anything. This surface did not start out as smooth as the oak border, and =
the sanding did give it the slightest "white" cast (dust) when viewed at th=
e right angle against the light. =A0
>
> I'm wondering if using the 600 paper is likely to bite me in the ass in a=
ny way later. Does the next coat of poly need more roughness to adhere? Am =
I giving up the chance to more thoroughly smooth the main area?

220 between coats is fine enough and gets the job done
fast. If you want a gloss finish, use lacquer or shellac.
Either one is harder than poly and rubs out better.

Greg Guarino wrote:
> Finishing the desktop I've mentioned elsewhere. I'm using very
> pedestrian stuff: MinWax Poly.
>
> I made a test piece using the three types of wood that make up the
> desktop. For the test piece, I sanded to 220, wiped with mineral
> spirits, and applied Semi Gloss poly. I then put on two coats of
> Satin Poly, lightly machine sanding with 220 in-between. I liked the
> results, except for some run marks that probably resulted from too
> thick a coat plus hanging the test piece vertically.
>
> Why two different glosses? A friend of mine did something similar on
> some flooring with good results, plus I had some semi laying around.
> I don't know if using semi for the first coat had any practical
> effect, but I decided it couldn't hurt.
>
> I've now got two coats on the actual project. Not content to leave
> well enough alone, I varied the procedure just a little bit. I again
> sanded to 220 and applied semi gloss first. That was Saturday. I had
> a (music) gig Sunday afternoon, so I got up early to see if I could
> get in another coat. Our house is attached, and thought the power
> tools at 7:30 in the morning might not be appreciated next door, so I
> decided to try hand-sanding at least the edges.
>
> I used 400 grit, which I had never tried before. As the edges are
> rounded, I used it without a block, just with fingers. It gave the
> edges (oak) a lovely smooth feel. I decided to do the whole surface
> with the 400, using a block for the large area. I then applied
> another coat of satin.
>
> I took a look at the result after my gig. It's coming along. I
> decided not to take on putting on another coat tonight, but I
> couldn't resist sanding it a tad, to see what the feel would be like.
>
> So here we're coming to the question, finally. I again used a small
> piece of sandpaper in my fingers for the edges, but decided to try
> 600 grit. I figured if it didn't adequately knock down the small
> amount of roughness that remained, I could go beck to the 400.
>
> I was surprised by the result. It smoothed the surface nicely, but
> didn't appreciably dull it. It looks and feels quite nice, even
> though I plan to add at least one more (and likely another) coat.
>
> I used the same 600 grit on the large surface area, using a block
> with a piece of scotch-brite in-between the block and the paper to
> "soften" the block. I don't know if this made any sense at all, but
> it didn't seem to hurt anything. This surface did not start out as
> smooth as the oak border, and the sanding did give it the slightest
> "white" cast (dust) when viewed at the right angle against the light.
>
> I'm wondering if using the 600 paper is likely to bite me in the ass
> in any way later. Does the next coat of poly need more roughness to
> adhere? Am I giving up the chance to more thoroughly smooth the main
> area?

Sanding varnish between coats does two things:
1. removes nibs/runs
2. abrades the surface so the next coat has something to stick to
A grit of 220-240 is plenty fine for that, 600 & 400 are pointless unless it
is necessary to even up the surface before final polishing.

It isn't necessary to sand for adhesion *IF* you recoat within a particular
time interval...4-8 hours IIRC, tells you on the can. I generally put on
3-4 coats (not wipe on), all the same day.
________________

All clear coats begin life as glossy. That sheen is modified by adding a
flatting agent. The more flatting agent, the less sheen. Those agents not
only decrease sheen, they decrease - very slightly- transparency; therefore,
some people (not including me) use only glossy to build and a less glossy
one for the final coat.

As you discovered, different grits give different sheens. Grits are
available up to at least 12,000. For final finishing one is better off
using a flexible pad; in the case of pumice/rotten stone, a felt pad; easier
is FFFF steel wool followed by a coat or two of paste wax...that won't give
you a high gloss like pumice/rotten stone but it *IS* easy and gives a nice
sheen.
__________________

Father Haskell said that shellac and lacquer are harder than poly and rub
out better. I agree with the last, not with the first.

The problem is, what constitutes "hard"? To me, it implies resistance to
deformation and that implies inflexibility. Like glass. One wants some
flexibility in a clear coating. A spar varnish is flexible but one also
wants scratch resistance and spar varnish doesn't have that. AFAIK, the
most scratch resistant, one part clear finish is oil base poly non-spar
varnish.

--

dadiOH
____________________________

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