Raised Glue Lines

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



Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
RE: Subject
As the old saying goes, patience is a virtue.
I often wait a couple of month between glue up and final finishing of a top, but then again, I'm not doing it for money.
Lew
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@yahoo.com wrote:

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.
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.

What do you think of resin glue like the type Marks always uses? http://www.highlandwoodworking.com/index.asp?PageAction=VIEWPROD&ProdID 59
Thanks!

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
GarageWoodworks wrote:

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
____________________________
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.?.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
GarageWoodworks wrote:

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
GarageWoodworks wrote:

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
SonomaProducts.com wrote:

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
____________________________
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.