Veneer Plus Contact Cement Plus Lacquer Equals Malfunction
Veneer Forum members help troubleshoot a project gone bad. October 17, 2012
Question
A few months back we completed a commercial office build-out, and part of it was a veneered reception wall. I sourced this out to a reliable company. The original piece was paper backed maple veneer on particleboard substrate with contact cement as the adhesive. We finished it, installed it, and a couple of weeks later got word from the client that the veneer was buckling slightly. Of course, the finish amplifies the effect making look terrible.
At that point, my source called his veneer supplier who informed him that the wrong type of veneer was used for that application, and recommended he use wood-backed veneer. This seemed logical in that this seemed like a more dimensionally stable product.
Some time elapsed and we received the remake. We finished it, installed it, and guess what - I received the same phone call from the customer, only this time it is much worse than the first time! We used pre-catalyzed lacquer for the topcoat, and dusted it with toner to achieve the color. What's going on here? I want to get it right this time!
Forum Responses
(Veneer Forum)
From contributor P:
Could you be more specific in describing your problem? The type of adhesive and the substrate – are they balanced?
From the original questioner:
As noted, the adhesive was contact cement, and the substrate was particleboard. The sheets were not balanced. The "wall" was about 8' long x 4' 6" tall x 6" deep. It was constructed with a series of vertical ribs between the front and back faces, so the thinking was that balancing was not an issue because the faces were mechanically stabilized.
From contributor Z:
Sorry you are having so much trouble with this wall. It seems your reliable company doesn't know much about veneering. First off, you always need to balance a panel (remember, that wood movement has been used to shear solid rock). Second, contact cement is almost never a good adhesive for veneer - too flexible. Third, forget the paper backed or phenolic backed stuff, use raw veneer. I suspect that your problem has been caused by reaction between your finish and the contact cement. That won't happen with PVA or AR glue.
From contributor O:
I don't think there is a situation where contact cement and any sort of veneer should be used together. The situations where unbalanced construction is ok are rare, but probably out there somewhere.
Do a search here for contact and veneer, and you will see you aren't the first with this tale of woe, unfortunately. I also suggest you don't believe the mass marketers of veneer that endorse contact as a way to lay up their product. The company you used may be reputable, but contact would not be considered good practice in any professional shop.
Oddly enough, with the advances in veneer slicers, mass production and better glues, veneered furniture was a boom product in the early 20th century. Any old casework was dolled up with QSWO or any nicer veneer and sold to the buying public. The veneer soon peeled, chipped, and bubbled due to the poor practice (square edges and corners all veneered). This gave veneer a reputation as weak that you may still find as you offer solutions to your customers today.
From contributor B:
Lacquer and contact cement is a sure-fire recipe for failure. Either lose the lacquer or the contact cement (or both). Raw veneer? I don't think so. Sounds like you need dimensionally stable laminated sheets. Maybe the phenolic backed veneer might have been a better choice after all, or the internal membrane stuff? Even the "peel-n-stick" should have been ok. I believe however that you shot yourself in the foot with the lacquer. Even the fumes are a highly affective adhesive remover.
From the original questioner:
I might disagree with the notion that the lacquer is the issue. This project sat in my shop for days before the install, and the problem occurred two weeks after installation. I highly doubt the lacquer seeped through the veneer and affected the contact cement. If this were the case, I'm sure I'd see an instant reaction. It really takes a good soaking and a little elbow grease to loosen contact cement from a wood surface. I can see however that contact cement might have too much elasticity to handle slight wood movement. Can anyone elaborate on this element?
From contributor G:
Your bond is flexible, your substrate is stable and rigid. Your veneer will see surface tension from the cured lacquer and thus will shrink relative to the substrate. The veneer will move at a different rate as well if using contact cement. That is why you see ripples or light crazing in your finish. The veneer is buckling as the finish cures and contracts. You need a near rigid bond between the veneer and substrate, they must act as one. Now you have to do both sides to balance the panel. Finish is required on both sides as well. I have even caused an unsupported panel to cup by excessive finish and hand rubbing on one side. Whatever you do to one side, you have to do to the other.
From contributor T:
I disagree with most of the answers so far. Contact works fine to stick sheet veneer products to substrate but it has to be pressed pretty hard. I usually use the corner of a wood block just slightly rounded off to press veneer, not a roller. Second, your description of your walls as balanced with ribs being the center of some complicated panels sounds adequate. Third, the people that are telling you not to use lacquer over this type of lamination are correct. Lacquer over veneer over contact is a sure recipe for failure. Conversion varnish works fine. I have no fancy scientific explanation for the preceding three points, just experience in doing it different ways. Both paper-backed and wood backed (NBL, 2 ply) veneer will work fine.
From contributor T:
In reply to your point about thinking if it was the lacquer causing the problem, you would see an immediate effect - this is not true. Sometimes it takes a week, sometimes a month. Believe me, I have done it wrong enough times to know! I have had to redo a couple of projects because of this. I did everything the same, but took it to a finisher that sprayed it with CV instead of doing it with lacquer myself. The CV finished projects are still good a number of years later.
From contributor E:
I have had many failures with paper backed and wood on wood backed veneer. What works for us is a heavy paper backed veneer (.22mil) or phenolic backer. It becomes kind of like a laminate (available from most veneer suppliers). We use a spray adhesive rather than the brush/roll on adhesive.
From contributor C:
Is your wall exposed to direct sunlight or near a heat source by chance? It has been my experience with veneer and contact cement that exposure to direct sunlight or a heat source will cause the veneer to shrink and the contact not being a rigid glue lets go when soften slightly by the heat!
A balanced sheet is the way to go and use different glue and as noted finish both sides. You most probably won’t get a call back except for more work. I learned these things by trial and error and through experience. Just add it to the cost of the job because this way the customer pays for it and not you.
