Solving a Dimpling Issue in a Small Veneering Project
Dimples in a finished veneered panel seem to be traceable to issues with the substrate and the adhesive. September 6, 2010
Question
Problem: many dimples in veneer.
1. Red oak, cut on bandsaw and edge glued prior to veneering. 1/16" thick (sanded on Performax).
2. Method - solvent based contact adhesive, 2 coats, applied with adhesive roller cover. 25 minute drying time between coats. 30-35 minutes last coat. Pressed out with j-roller (I know, not the best).
3. Days later ran through Performax 120, 180 grits.
4. Used scraper plane for final leveling.
Applied stain and then saw the problem: tons of pencil sized craters or dimples throughout the veneer (veneer ended up being sanded in one corner, so I will start project from scratch).
What is the most likely cause of dimples in shop-made veneer? No bumps - just depressions. Could simply having sanded the veneer to far too thin a layer been the cause, considering I used contact adhesive? I've no vacuum bag and am not sure how thick of a veneer I could heat up with an iron, using PVA glue. This project is 19" wide and 6' long.
I would have preferred to use other methods, but I think I need to just refine the technique of using contact cement. I want the results to be defect free - no waviness, dimples, etc.
Forum Responses
(Veneer Forum)
From contributor N:
Contact adhesive and thick veneer is not a good match to start with. My guess is you need a different adhesive.
From contributor B:
The Performax sanding system may have been part of the problem. My Performax heats the wood quite a bit when I am sanding and heat and contact cement don't go together. Thick veneer and contact also don't go together. Try regular glue and a vacuum bag and you will be miles ahead. You are wasting your time on refining your contact cement technique, as there is nothing refined about contact cement.
From contributor G:
Solvent based stain and contact cement don't go together, either.
From contributor B:
I was thinking the same as others. If you are stuck with contact cement, best find some paperbacked veneer. Jonathan Benson's veneer and inlay book might be a good purchase if you don't want a vac press.
From contributor X:
Just what was the base like? What were you applying the veneer to? Did it have defects like bubbles, softness, etc.?
From the original questioner:
Thanks. I'm suspicious of the contact cement as well, as I know it's not the ideal method. The substrate was 3/4 veneered plywood. Like nearly all veneered plywood, it has less than a perfectly flat surface - there are undulations or slight bumps and valleys throughout, but they are definitely not similar to the defect in the veneer's surface that I ended up with.
I've got a rotary vane vacuum pump, leftover from my days doing air conditioning. I could use that with a vacuum bag, correct? I'm going to use 3/4 MDF for the re-do.
What's the thickest veneer that could work white glue or PVA and an iron? I'm guessing shop-made veneer would be too thick to pass the heat, correct?
From contributor W:
You can use the rotary vane pump such as a J/B or Robinair. That's what I just used to build my system - it's a J/B 7 CFM unit and it works like a dream. I bought everything except the pump from this place. They have a builder's kit which has all the hardware, then you need to order the size of the bag you need and make a decision on the plastic used in the bag. I bought the polyurethane bag - DuraMax elite, and it's very tough. I veneered a curved piece that had sharp corners (won't do that again), but the bad came through fine. You will also want to use the cold press glue since it dries to a very hard glue line with no creep.
From contributor E:
I have no idea if this is appropriate to your needs (size of work), but there is lots of furniture out there built over the centuries that has veneer that thick, done with hot hide glue and a veneer hammer. The glue, unlike PVA and contact cement, is stainable, and in fact the outer surface is lubricated with hide glue when it is applied, leaving a nice primed surface for woods that tend to blotch in staining.
From the original questioner:
Thanks to everyone! I picked up 2 quarts of cold press glue from a not-so-nearby Woodcraft store and did a small test piece of veneer. It came out perfect! Typical temp in my shop this time of year is 62-66, so the cold press glue will work just fine and I'm okay doing the veneering job I've got to tackle, by using cauls. I've also chosen MDF as the substrate and will veneer both sides. I appreciate everyone's comments!
