What causes raised glue lines? I have done two projects where this has
cropped up on me. One was a cherry table and the other a walnut dresser.
Days after sanding (and varnishing) I noticed a small ridge at the glue
line. This was not there after sanding and finishing. What causes this?
I googled and read that wet lumber can cause this, but I am skeptical of
this. I have seen this with TitebondIII and Elmers Wood glue.
--
www.garagewoodworks.com
GarageWoodworks wrote:
> What causes raised glue lines? I have done two projects where this has
> cropped up on me. One was a cherry table and the other a walnut dresser.
> Days after sanding (and varnishing) I noticed a small ridge at the glue
> line. This was not there after sanding and finishing. What causes this?
> I googled and read that wet lumber can cause this, but I am skeptical of
> this. I have seen this with TitebondIII and Elmers Wood glue.
>
IMO, the issue is not wet vs. dry wood. I believe that the ridge results
from slightly differing expansion of each piece in the glue up which
reflects difference in how each board was originally sawed from the log.
If one board of the glue up pair is flatsawn, it means that the glue
edge is quite stable, almost appearing quarter sawn. It won't expand
it's thickness much as it absorbs and gives up moisture (which
continually happens, regardless of the finish). If the other half of the
glue up is quartersawn though, then its' corresponding glue edge is
essentially flatsawn, and it will expand and contract through the
moisture cycle more than it mate . . . We're talking minute difference
here since the we're talking about the thickness of the boards, not
their width, but I believe that the difference is enough to feel as a
"ridge" as the original poster described. Most boards are not fully
quartersawn, or at the other extreme, flatsawn, but I think the
principle is correct.
Rick
1. Moisture from glue enters wood.
2. Wood expands
3. Glue dries
4. Woodworker sands or scrapes wood and glue line to an even plane
5. Moisture in wood finally completly dries
6. Wood shrinks (slightly)
7. Glue does not shrink
8. Woodworker feels small ridge at joint.
Not consistenet due to many factors including angle of grain at glued
face of wood which affects moisture absorbtion and expansion
direction, current moisture of various areas of wood, etc.
I don't think waiting a month but a few days with good airflow and
reasonable temperature should help. If it is high humidy season the
problem could actually show up in a different season I suppose.
P.S. all conjecture on my part.
On Nov 21, 5:55 pm, "GarageWoodworks" <.@.> wrote:
> What causes raised glue lines? I have done two projects where this has
> cropped up on me. One was a cherry table and the other a walnut dresser.
> Days after sanding (and varnishing) I noticed a small ridge at the glue
> line. This was not there after sanding and finishing. What causes this?
> I googled and read that wet lumber can cause this, but I am skeptical of
> this. I have seen this with TitebondIII and Elmers Wood glue.
>
> --www.garagewoodworks.com
> Both wet the wood. The wood swelled (swoled? :). You sanded flat.
> The wood dried. The wood (but not glue) shrunk.
>
> Solution: wait a month after glue up to sand.
>
> --
>
> dadiOH
I'll buy that, but a month? The thing that kills me is that it doesn't
always happen. It doesn't always happen at every glue line (if multiple
boards are glued up in a table top) or down the entire glue line. The 'fix'
is easy because the ridge is VERY small and only slightly felt when you rub
your hand over it. All I do to fix it is sand off the finish and re-finish.
Just a PIA.
Do most people wait a few weeks before sanding? I have read that plastic
resin glue does this to a lesser extent.?.
GarageWoodworks wrote:
> What causes raised glue lines? I have done two projects where this has
> cropped up on me. One was a cherry table and the other a walnut dresser.
> Days after sanding (and varnishing) I noticed a small ridge at the glue
> line. This was not there after sanding and finishing. What causes this?
> I googled and read that wet lumber can cause this, but I am skeptical of
> this. I have seen this with TitebondIII and Elmers Wood glue.
>
IMO, the issue is not wet vs. dry wood. I believe that the ridge results
from slightly differing expansion of each piece in the glue up which
reflects difference in how each board was originally sawed from the log.
If one board of the glue up pair is flatsawn, it means that the glue
edge is quite stable, almost appearing quarter sawn. It won't expand
it's thickness much as it absorbs and gives up moisture (which
continually happens, regardless of the finish). If the other half of the
glue up is quartersawn though, then its' corresponding glue edge is
essentially flatsawn, and it will expand and contract through the
moisture cycle more than it mate . . . We're talking minute difference
here since the we're talking about the thickness of the boards, not
their width, but I believe that the difference is enough to feel as a
"ridge" as the original poster described. Most boards are not fully
quartersawn, or at the other extreme, flatsawn, but I think the
principle is correct.
Rick
I appreciate your response and explanation, but if I understand your
explanation correctly, your 'ridge' would look like
is: --------__________
My 'ridge' looks like this: -------^---------
It is as if a tiny ridge or bump (about the size of a hair but noticeable by
touch) exists at the glue line with both faces of the joining wood remaining
in the same plane.
> W/ PVA glue, the most notable cause is creep in the glue itself, not
> moisture or expansion. Best way to minimize the effect is to ensure
> tight-fitting joints and thin glue layer, hence minimizing the thickness
> of the ending glueline. Insufficient clamp pressure can help cause the
> problem by leaving thicker glue line.
Ok. I look into this. Thanks. I thought I was going crazy! I sanded
to a smooth wood surface, and put on a nice smooth poly finish, only to have
a ridge at the glue line weeks later! VERY frustrating. It has happened to
me twice now.
> The is the possibility of wood contraction from drying, but that is
> normally not revealed by the single bead of protruding glue along the
> glueline that the creep effect causes.
>
> While it's a pita to work with, the thing that will eliminate this effect
> almost completely is one of the polyurethane glues (although you then have
> the foaming issue to clean up after). Hide glue isn't as bad, either.
What do you think of resin glue like the type Marks always uses?
http://www.highlandwoodworking.com/index.asp?PageAction=VIEWPROD&ProdID=1659
Thanks!
>
> --
On Nov 24, 6:16 am, "dadiOH" <[email protected]> wrote:
> SonomaProducts.com wrote:
> > 1. Moisture from glue enters wood.
> > 2. Wood expands
> > 3. Glue dries
> > 4. Woodworker sands or scrapes wood and glue line to an even plane
> > 5. Moisture in wood finally completly dries
> > 6. Wood shrinks (slightly)
> > 7. Glue does not shrink
> > 8. Woodworker feels small ridge at joint.
>
> > Not consistenet due to many factors including angle of grain at
> > glued face of wood which affects moisture absorbtion and expansion
> > direction, current moisture of various areas of wood, etc.
>
> > I don't think waiting a month but a few days with good airflow and
> > reasonable temperature should help.
>
> I think the dry period depends on how things were glued up. I've
> never experienced the problem gluing relatively thin boards to make a
> wider one but I have when gluing those same type of boards to make a
> thicker one. Logical since the latter uses many times more glue and
> the center of the glued up boards is much farther from the surface.
> Glue up a 3" thick slab from 3/4" x 3" boards and it is going to take
> a long time for the moisture to dissipate.
>
> --
>
> 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 athttp://mysite.verizon.net/xico- Hide quoted text -
>
> - Show quoted text -
How about applying the pressure listed in FWW last month. I am pretty
sure there wouldn't be enough glue left in the joint to ever feel. :)
Daryl
On Nov 21, 8:55 pm, "GarageWoodworks" <.@.> wrote:
> What causes raised glue lines? I have done two projects where this has
> cropped up on me. One was a cherry table and the other a walnut dresser.
> Days after sanding (and varnishing) I noticed a small ridge at the glue
> line. This was not there after sanding and finishing. What causes this?
> I googled and read that wet lumber can cause this, but I am skeptical of
> this. I have seen this with TitebondIII and Elmers Wood glue.
>
> --www.garagewoodworks.com
Wet is a relative term. Even properly dry lumber goes through changes
with seasons and relative humidity while the cured glue does not.
That is as far as I can help. Does anyone have good strategies for
combating this?
Daryl
GarageWoodworks wrote:
> What causes raised glue lines? I have done two projects where
> this has cropped up on me. One was a cherry table and the other a
> walnut dresser. Days after sanding (and varnishing) I noticed a
> small ridge at the glue line. This was not there after sanding
> and finishing. What causes this? I googled and read that wet
> lumber can cause this, but I am skeptical of this. I have seen
> this with TitebondIII and Elmers Wood glue.
Both wet the wood. The wood swelled (swoled? :). You sanded flat.
The wood dried. The wood (but not glue) shrunk.
Solution: wait a month after glue up to sand.
--
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
On Nov 21, 9:50 pm, "[email protected]" <[email protected]> wrote:
> Wet is a relative term. Even properly dry lumber goes >through changes with seasons and relative humidity >while the cured glue does not.
True, true. I have finished things that are as the lumber guy called
it "case hardened" (like metal) and they seem to dance for sometime.
The boards were dry on the outside, and even seemed so on the inside,
but with a good moisture detector and a fresh end cut, it was not so.
> That is as far as I can help. Does anyone have good >strategies for combating this?
This could be a good thread. I hope many chime in. My method is to
buy the wood as far in advance as I can, even though it cramps my
storage space. Let it continue to dry, and to get to a comfortable
humidity to your area. Standard rule of thumb is one year per inch,
so I figure if the hardwood guys have it is probably about 3 - 6
months from being cut when shipped.
I put it in the shop for another six months or so before starting the
project.
Then after the woodwork part of the project is finished, I put it in
the house for another month or so. Your house will usually have
significantly less humidity than the shop f or assembly area, so the
wood will continue to move.
After that, a final sand, then start in with the finishing. Make
sure you finish BOTH sides (even if you don't sand the unseen areas to
death), whether it is seen or not as it will let the wood outgas and
dry the same on both sides to help minimize movement.
I have also found that the six months in the shop before final planing
seems to help with tear out on woods like hard maple and black walnut.
Robert
[email protected] wrote:
> On Nov 21, 8:55 pm, "GarageWoodworks" <.@.> wrote:
>> What causes raised glue lines? I have done two projects where this has
>> cropped up on me. One was a cherry table and the other a walnut dresser.
>> Days after sanding (and varnishing) I noticed a small ridge at the glue
>> line. This was not there after sanding and finishing. What causes this?
>> I googled and read that wet lumber can cause this, but I am skeptical of
>> this. I have seen this with TitebondIII and Elmers Wood glue.
W/ PVA glue, the most notable cause is creep in the glue itself, not
moisture or expansion. Best way to minimize the effect is to ensure
tight-fitting joints and thin glue layer, hence minimizing the thickness
of the ending glueline. Insufficient clamp pressure can help cause the
problem by leaving thicker glue line.
The is the possibility of wood contraction from drying, but that is
normally not revealed by the single bead of protruding glue along the
glueline that the creep effect causes.
While it's a pita to work with, the thing that will eliminate this
effect almost completely is one of the polyurethane glues (although you
then have the foaming issue to clean up after). Hide glue isn't as bad,
either.
--
SonomaProducts.com wrote:
> 1. Moisture from glue enters wood.
> 2. Wood expands
> 3. Glue dries
> 4. Woodworker sands or scrapes wood and glue line to an even plane
> 5. Moisture in wood finally completly dries
> 6. Wood shrinks (slightly)
> 7. Glue does not shrink
> 8. Woodworker feels small ridge at joint.
>
> Not consistenet due to many factors including angle of grain at
> glued face of wood which affects moisture absorbtion and expansion
> direction, current moisture of various areas of wood, etc.
>
> I don't think waiting a month but a few days with good airflow and
> reasonable temperature should help.
I think the dry period depends on how things were glued up. I've
never experienced the problem gluing relatively thin boards to make a
wider one but I have when gluing those same type of boards to make a
thicker one. Logical since the latter uses many times more glue and
the center of the glued up boards is much farther from the surface.
Glue up a 3" thick slab from 3/4" x 3" boards and it is going to take
a long time for the moisture to dissipate.
--
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