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Glue Choices for Applying Veneers

Pros dig into the fine points of glue selection for veneering, compare the qualities of different adhesives, and discuss veneer application techniques. October 1, 2005

I'm re-veneering a maple dresser top for a customer that has a burn mark (wouldn't sand out) from a lamp. Contact cement is made for laminate, but what is best for veneer? I saw a post a few months back that addressed this issue, but can't find it. I don't want any checking or problems. Does anyone have any suggestions?

Forum Responses
(Cabinetmaking Forum)
From contributor F:
PVA (Poly Vinyl Acetate) which is both the common yellow glue and the more water proof white version is the mainstay of veneering these days. (I read recently that the term Aliphatic Resin is actually meaningless and that yellow glue is actually PVA.)

Also used commonly is urea formaldehyde two part glue which can be mixed with more or less of its catalyst to adjust the amount of open time you have before the pressure is applied. Also used and extremely waterproof is two part resorcinol glue which is usually brown in color.
Contact cement isn抰 usually used by folks that truly know the business of veneering.

From contributor T:
To contributor F: I've heard a lot of talk against contact cement for veneer and I haven't veneered anything for years. But in the mid 70's I was building walnut cabinets for Emu music systems and I used contact cement for the veneer. I think in those days that's all there was really (never heard of vacuum clamping back then). Anyhow, I never had a complaint or to my knowledge, a failure. I still have some big speaker boxes I veneered in 1970. They look fine too so it does work.

From contributor P:

Contact can work but it is not recommended as the odds are much greater that it will fail. Maple is much more likely to fail. Plastic resin glue is good also.

From the original questioner:
To contributor P: What is plastic resin glue and how is it used? The top I'm veneering is about 16" x 72 and has either pre-cat or CV finish which has come off in a few places in small streaks due to being used for a lizard terrarium. I wasn't planning to sand off all the finish, just scuff it. What do you guys think? Is the peel and stick veneer contact cement glue? I don't have a vacuum press or bag but could clamp it in particle board.

From contributor F:
To contributor T: Veneer presses have been around for quite some time. Before that, animal hide glue was used in a process known a hammer veneering. Vacuum presses and contact cement are fairly new. I think the main problem with contact cement is its viscosity. The unevenness of the glue itself will telegraph itself through thin veneers. I also think it is too soft setting and will allow creeping. Other than that, the good points are that it is waterproof and long-lasting. I have seen post formed counter tops that were made in the 1960's that as far as adhesion is concerned are as good as new. I have seen laminate come loose from the substrate when early water base contact cement was used.

From contributor J:
To the original questioner: You asked for the best glue to use. The answer is Urea resin (plastic powdered resin) it is dehydrated urea formaldehyde. It is rigid, permanent and can not be reactivated. It drastically reduces checking.

There are two primary families of adhesives used in wood veneering today (PVA's and Urea).
Urea, like concrete when it dries is rigid and permanent - think plywood (it is made with urea adhesive) and it cures by chemical reaction.

Pre-cat PVA's give you a little of both, more rigid than PVA and a little more malleable than Urea. They are the compromise adhesive but are not to be used with maple.

PVA poly vinyl acetate (aliphatic) behaves like candle wax. It can get solid but can be reactivated by heat and high humidity. When this happens, the glue can lose it's grip a bit, thereby allowing for bubbles and checking.

Contact is more easily reactivated by heat especially with today抯 thin veneer. It also can be activated and lose its grip with some finishes. (I suspect those speakers were made with 1/8 or thicker veneer something we would call lumber today. Also, you were forced to hammer many years ago if you did not have a hydraulic. We have a PVA today that can be hammered like the old hide glue).

From contributor F:
To contributor J: Are you saying PVA should not be used with maple veneer on just pre-cat PVA or both and why? Why just maple?

From contributor P:
PVA is thermal glue - it can be reheated and it works fine. In fact it could use Titebond paint it on and let it dry and then come back and iron it from the face and reheat the glue and it will work. But I wouldn't recommend it for a big surface.

Plastic resin glue is thermal set glue which means it cannot be reactivated. It is really cool on curved pieces as there is no spring back. I did some curved veneered doors out of cherry that I sent to Yuma Arizona and was concerned. There was no problem at all using plastic resin glue. Maple is so dense that it expands and contracts more than most woods and so requires the best glue.

From the original questioner:
One of my suppliers now is swearing by FSV glue which he says is a water base PVA and great for veneering maple. I can't find a supplier in Arizona who has urea resin glue.

From contributor J:
Contributor F - Precatalyzed PVA's have an ingredient that can react with maple. The reaction can result in a pinking of segment of the maple. Granted this doesn't happen 100% of the time but can and does happen.

Maple, being a dense species, does not wet out well. A PVA, especially a thicker viscosity PVA, will have less water - thus less wet out and less grip. With less grip on the veneer and the inherent tension and stress of maple, it can more easily pull on a PVA glue line resulting in checking, cracking and blisters.

To the original questioner: FSV is indeed a PVA based adhesive. It has what the back room tech's call increased tackifiers and modifiers.

Anyhow, it was brought about for a few reasons;
1. Folks like the fast bond of contact, so we needed to develop a glue to give them that fast tack with a PVA and offer a better glue line when it comes to wood veneer.
2. It was developed to use with paperbacked veneer and again, offer a better bond than contact. Ideal for that last sheet at a field install.
3. You can hammer veneer with it.

4. It was tinted pink so the guys in the shop wouldn't have to drastic a shock when they were asked to try glue different than the Wilsonart spray contact product that is pink.

From contributor S:
1. Urea or plastic resin adhesive is not good to use unless you can clamp the entire surface 100% flat for at least four hours. If you have a ripple in the surface it is going to be hard to sand out without sanding past the veneer. Urea or plastic resin adhesive can not be mixed to adjust open time there is a formula to mix according to or you can end up with problems. Like lumps or excessive bleed through. Urea or plastic resin adhesive works best in a vacuum bag.

2. Yellow has the same problem as with urea or plastic resin adhesive. Again you have to pressurize the entire surface 100% the same everywhere or you will develop dents and ripples.

3. Veneer grade contact can work if (1) you use two ply veneer so the little bumps from spraying the contact on don抰 telegraph and (2) if you seal the veneer with shellac sanding sealer before finishing it. With both the yellow and urea adhesive you need to make a MDF blank and then laminate the blank on the underside so if the glue bleeds through it will not stick to the MDF.

The veneer needs to be oversized so if it moves it can be trimmed later. Roll the adhesive on the item to be veneered so it is even. Place veneer and then place the MDF. Load the MDF blank with weights from the center out. Wait four hours. Remove weights leave for twelve hours before finishing. Don抰 roll contact adhesive it never comes out even - spray it. Let it dry to the point where it feels just slightly tacky. Watch out for dirt as even a little bit will cause major bumps in your work.

From contributor R:
I would suggest rolling out a good coat of white glue on the veneer and the top to be veneered. Let it dry overnight. Place the veneer on the top, put down a piece of aluminum foil on the top. Set an iron on cotton and iron the bad boy down. Piano tops veneered years ago look the same today as they did years ago - no bumps, no lumps, and no hollow spots.