Gluing to Pre-Finished Plywood
Nothing seems to stick to the UV-cured finishes on pre-finished plywood. March 25, 2010
Question
Has anyone found a glue that will stick to the UV-cured material being used on pre-finished ply? I've tried all the normal stuff: epoxy, gorilla glue, roo glue, yellow and white glue, and even superglue. All of these will pop right off the UV finish, and don't even leave any residue. In a couple of cases I was able to make do with the thin plastic double-stick tape but it was more for positioning than for strength.
Forum Responses
(Adhesive Forum)
From contributor A:
Anything that will stick to the finish will peel the finish off of the wood when destructively tested. Some people go with the staples/screws no glue approach. We use dados/rabbets for alignment so gluing is not an issue for us.
From the original questioner:
I'm hoping to avoid any destructive testing! I too use the dado/rabbet methods but even though you can put glue on the female joint sidewalls, when you insert the pre-finished panel any glue in that area isn't going to stick to the finish and won’t add anything as far as strength. I just spent half an hour on the phone with 3M and they told me that many of the pre-finishes have silicone in them and therein lies the problem. The only recommendation they had was for their #4693, which is a plastics-type adhesive but it might stick to the UV finish, and it will also bond to wood.
From Gene Wengert, forum technical advisor:
If you fasten something to the finish and that bond is really strong, then the overall bond strength is only the bond between the finish and the wood. In other words, the adhesive that fastens to the finish can be really strong, but the joint can fail because the finish is not strongly attached to the wood.
From the original questioner:
Good point and one that I had completely overlooked. The whole issue seems a bit less important now.
From contributor M:
Everyone is right about the bond of the finish to the wood being the weak link, but don't underestimate that bond! By the way, Roo glue will not bond prefinished well. I have tested it and it just pulls apart. Roo glue does, however, bond to pre-cat shockingly well. I worked at a cabinet shop once that used Roo to glue their drawer fronts onto the drawer boxes (both finished with pre-cat), and then a few screws for insurance. Once I had to remove a cured joint to re-adjust the drawer front, and it was nearly impossible to remove it without breaking something. But when the joint did break, 100% of the lacquer came off the drawer front where it was in contact with glue. I would have never guessed it to be so strong.
