Wood Veneer on MDF: How Thick Is Too Thick?
Craftsmen report problems using thick wood veneer on an MDF substrate. June 9, 2007
Question
Occasionally I have a need to do a stain grade wood countertop or bench top with a solid wood border. I now refuse to bind solid wood in a mitered frame because I know nature will win and the frame will burst come summertime. On the other hand, I don't like the durability of a 1/32" veneer over MDF. One deep scratch and you can never really repair it. (I also don't want an expansion joint in the top.) So, what about veneering 1/8" solid wood on MDF? Or even 3/16"? At what point in thickness does the thick wood "veneer" begin to behave too much like solid wood and overstress the glue joint to MDF? Would yellow glue be the way to go to bind the 1/8" solid stock to the MDF substrate?
My guess is that a very thin veneer is still trying to expand and contract, but the glue is easily strong enough to overcome such a small expansion force. I'm guessing that if you double the thickness of the veneer, you roughly double the movement force. I wonder at what point the glue loses to the stress of the wood movement.
Forum Responses
(Furniture Making Forum)
From contributor S:
Perhaps you could experiment with some pieces of various sizes and a warmish oven and be the first guy to put out some data on this thinly covered issue!
From contributor B:
I did this on a project with 1/4" thick hard maple. They were 9" x 12" plaques with the hard maple thick skin applied onto an MDF backer. When these plaques were placed in heated rooms (low humidity), the maple curled and pulled away from the MDF at the ends. This was a serious failure. You could place a damp cloth on the face of the curled plaque face overnight and in the morning it would be lying flat again.
I then tried the same thing with 1/8" hard maple. Whereas the wood was no longer strong enough to pull away and curl at the ends, it still failed. This time the maple split in the center.
So, my experience is that this is not a good idea with hard maple. Perhaps mahogany or some other very stable wood will work better, though.
From contributor C:
To the original questioner: I think you are right on with your thoughts. We have done a lot of applications where 1/16" or thicker veneers are glued on edges and top surfaces to allow for a faux solid top and get a nicely eased edge. Also have had very good luck with moisture resistant yellow glue. On the thicker laminates, say 3/16 to 1/4" thick, you can see the glue lines in the surface after some time, but not negatively. So yes, they are moving a lot more than the 1/16" veneers.
From contributor K:
I have done many projects with thick veneer in the range of 1/16" to 1/8". Over time I have become more cautious and prefer to stay at 3/32" or less. I have seen serious failures at 3/16" and over. I think the problems vary with the species used and its relative stability in service - vg doug fir is going to be better behaved (and glue better) than flatsawn rock maple. The best adhesives will have a rigid glue line. Yellow glue tends to creep under stress. I like to use epoxy for its long assembly time, water resistance and gap filling property. Urea formaldehyde is good also. Both will cure faster with added heat. If you use epoxy, be sure to sand the mating surfaces for good adhesion, particularly with dense hardwoods. I like to join leaves of veneer together with yellow glue and masking tape, then run the assembly through the widebelt prior to gluing it to the substrate in a vacuum press. You can also join the leaves together with tape on the substrate as you do the final glueup, but you have more pieces to deal with and may have a harder time getting an inconspicuous joint, as the glue you are using for the layup will ooze up through under vacuum.
From contributor E:
I made a pair of end tables and used Australian lacewood for the top. Since I only had a small amount, I resawed to about 1/4" and joined 3 pieces about 4" wide with Gorilla Glue. I laminated the entire thing onto some MDF core maple plywood (1/4") which was dadoed into a solid maple, mitered frame. It's been two years now and on each table, one of the joints has raised up and separated slightly. I don't know why - could have been the grain direction - but have decided to only use solid wood from now on, since there are a lot of unknown factors when you combine all of the different wood and grain directions. These pieces were put into a mitered top.
