Is it ok to use contact cement for wood veneer?
The short answer: sometimes yes, most of the time no. There are many complexities that are involved with this question, some of the variables are what kind of contact cement (i.e. the solvent; water based or not), what kind of veneer (paper backed or not, straight grain or wavy), what kind of finish are you putting on the veneer . . . the list goes on.
Why is contact cement bad for veneering?
Contact cement was originally invented for gluing plastic laminate. Although superficially similar to wood veneer in that you have a large thin piece of material to glue down, plastic laminate is a man made product that has no movement. It does not expand and contract with humidity like a wood veneer will.
Why does the kind of finish matter?
The kind of finish is very important because of the solvents used in the finish. For example, spraying lacquer on a veneer that has been glued down with regular contact cement will risk the veneer to unglue. This is because the contact cement is reactivated by the lacquer as it penetrates through the veneer.
The same principle applies for a water based contact cement, and a water based finish..
If I use a backed veneer, is that better?
Yes, if the veneer is paper or phenolic backed, this definitely helps stabilize the veneer from expansion, and more importantly, protect the finish solvent from penetrating through the veneer to the contact cement. But be aware that the edges of this veneer will be succeptable to lifting as they will be exposed, unless they are covered up by an edgebanding for example before finishing.
How to apply the veneer?
You must position the veneer exactly over the substrate properly because once the veneer is touched to the substrate you will not be able to shift the veneer (compared to if you were using a PVA glue for example). There is no play when using contact cement.
Lay thin pieces of wood or dowels across the substrate so that you can position the veneer over the substrate properly but without actually have the two touch. Then, press the veneer to the substrate on one side, and one by one pull out the pieces of wood, while at the same time pressing down the veneer with a j-roller or block of wood to make sure it is gluing properly to the substrate and that there are no air bubbles.
What is the most important factor overall when using contact cement for gluing veneers?
Definitely the finishing products you will be using. Getting the veneer properly laid down and glued on to the substrate is tricky, but not overly difficult, if you prepare yourself adequately.
Choosing the proper finishing products that won’t afterwards lift the veneer off the substrate (because the glue is reactivated by the solvent) is more important.