Glue Lines in Veneer

The veneer manufacturer should detect and eliminate glue lines; at the finishing stage, they are hard to deal with. March 26, 2010

We are having issues with glue lines in our veneer from our vendor. We can not seem to eliminate the lines, even after sanding with a good panel sander. Since we are using a waterbased finish, will we be more prone to lines that would have been covered up by solvent based finishes? Is there a good way to detect these lines? We thought we had eliminated the seams after sanding - you can't see them before finishing, but then after the second coat they appear, causing a very large headache.

Forum Responses
(Adhesive Forum)
From Jeff Pitcher, forum technical advisor:
You should talk to your vendor about their splicing process. Very often, veneer splicers use too much splicing adhesive when making faces, which results in a thick (visible) glue line. You also might want to check the MC of your veneer. If it's over 10%, this could be adding to your problems.

From contributor R:
This is an age old problem that has to be controlled on the supplier side. Your supplier should add a florescent dye to the glue. Wherever there is glue it will show up under black lighting and the supplier should sand it off. It is nearly impossible to see without this light and by the time you add a finish, it is too late.

From contributor B:
I had the same glue line problems with a line of unfinished conference tables that I import from China. I was able to easily spot them before finishing by turning off the overhead lights and lighting the table with two 500w quartz work lights placed at a maximum oblique angle. The next step is to find another supplier.