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Finishing cracks on veneer9/11
I did a fairly large veneer job a few years ago...looked great thru finish and install. Over a period of 2 years the finish developed significant cracks. There was a piece of veneer on an underside that did not get finished and it looks as good as the day it was veneered. I presume that we have a finish failure...the veneer appears to be bonded well in all of the cracked areas. Solutions for repair? Can we sand thru the finish and so long as we don't burn the veneer go straight to refinishing (don't want the cracks to reappear over time)? Or perhaps sand it down well, ensure a good bond on the old veneer and apply a new veneer layer? ...or strip down completely and start over?
This tends to be a bonding issue rather than a finish issue. What you should do is iron down the finish with a standard household iron. Then push down the finish with a wood block (not a roller), just as you would use a squeegee.
After you do this, use a new polyurethane finish. Polyurethane will be able to expand and shrink along with the veneer rather than trying to stay stable which is what likely caused your problem.
To clarify, I should iron down the cracked finish and squeegee it, scuff then top coat with Polyurethane? Will the existing (old) finish impact the flexibility of the poly? Would you recommend using an isolante barrier between the old finish and the poly?
So sorry - I should have started by saying that you should sand down to remove the finish without sanding into the veneer.
If you want to use a catalyzed finish, change to a 2 part urethane or standard urethane.
A barrier or vinyl sealer can help, but wouldn't be necessary with a standard urethane.
I like to use a scraper to remove finish in veneer before a light sanding.'nothing too aggressive mind you but is can cut down on the amount of sanding needed and hence the chance for burn through.
Can you tell the finish problem is caused by the veneer? What kind of finish? What kind of veneer? What adhesive was used? We need specifics if you want real help instead of speculations. Some finishes, especially precatalyzed lacquer has a maximum film thickness, and if exceeded, it will crack. No matter what you sprayed it on.
Contact adhesive did not flash off completely.
Underside, unfinished, same method of application and is OK, right?
If you use the contact, and it can be done, harder to get right than other methods tho, it needs to Totally flash off, or use phenolic back if you can. Or do the bag or press.
One other item to consider - How thick was the paper backing? 10 mil with contact cement is bound to cause problems. 22.2 Mil double paper-backing is a far better choice with contact cement.
I'm late to the party, but without seeing pictures, I'd bet that you laid on the pre cat too heavy on the top. The precat I use puts restrictions on how thick it can be. Too thick, you get cracks. N addition, I do not agree with using contact cement, but don't feel that is your issue based on what you describe.