I’ve searched the archives a bit and haven’t found a discussion of this particular problem so I thought I’d let others know:
I am faced with having to redo a dining table that I made a couple of years ago. This was a veneer job using shop sawn mahogany (quarter sawn), 3/32 inch thick over mdf. I used Unibond 800, a urea formaldehide glue. Over time, the edges of each veneer flitch curled up, a result of drying in our extremely dry winter climate. The table top now has small speed bumps at each flitch edge that run the length of the table. Having never faced a veneer failure like this, I guessed that I had a glue failure. Well, some exploration has shown that the glue was fine, in fact the failure is in the mdf itself. The curling veneer was able to pull a chunk of mdf up with it. I never expected this would happen…. just didn’t think the forces would be this great.
I am wondering if others have ever experienced a core failure such as this. I know that many people (including myself) have used thick veneer without any problem. However, you won’t catch me doing it again like this. If I choose to use thick veneer again I will either use a plywood as a core (as was suggested by Daryl Klein at Vacupress) or use a layer of cross-band veneer between the surface veneer and the mdf.
Replies
Bummer indeed. You have my sincere sympathy (empathy, mitgefuehl, "I feel your pain") I've had to eat a job or two myself, and I hate the feeling. We work hard enough for our money to have to do anything for free.
The main culprit is the grade of MDF, or perhaps the MDF wasn't up to spec. There are all kinds of grades and densities of MDF, and you have to have a pretty high grade for that application. A lot of wholesalers aren't very good about making the differences known, preferring to offer the cheapest gade available for making cabinet boxes & such.
Still, I'd rather use MDF or high grade particle board for a veneered table top. I've had too many problems with plywood voids and inconsistencies telegraphing through. Noibody I know uses plywood for a veneer substrate any more. Maybe if you could find a plywood with a high grade MDF face? Even though it's heavy and nasty, all the high end custom woodworkers I know ( and I do work with some big ones) use MDF or particle board for veneer cores. Particle board is used when stiffness is a factor, MDF the rest of the time. Standard practices usually evolve for a reason based on collective experience.
Just a thought.....
Michael R.
As you noted the winter extreme dryness most lightly caused this problem. I would suggest the finish may have been a little too porous and allowed the dry winter to "suck" the veneer dryer on the surface. What iswas the finish? I look around my house and this winter has added at least 100 nail pops. This house is 15 years old and over the last couple of years I had fixed and painted most of the rooms, got to do most again 'cause of the winter pops!!
Nigel. I had the same problem with my four bedroom colonial and I solved the problem by using drywall screws.
Put one each about two inches above and below every nail (Be carefull to not run the screws in so far as to break the paper.
Pull out any nails AFTER the screws are set. Spot prime with shellac over new screws (Before spachling)
Sorry to hear of this problem. While I've never experienced it, you might try MDO next time,ply with a smooth papered surface. You're right that 3/32 is mighty thick for a mahogany veneer.
Sorry to hear that Sophie,
I hope the same does not happen to a piece I did!
I veneered some cherry I resawed to some MDF a few years back and
so far it's ok.
But it's good to know that it can fail. The learning from mistakes
thing is tough but valuable. Particularly when we can all share
our mistakes and successes on these forums!
The next time I do such veneering I'll probably use HDF, much denser,
stronger and of course even heavier than MDF.
The MDO might work for resawn veneer but I think even that can telegraph
through thin commercial veneer.
Good luck!
Tom
Boss, actually MDF is engineered as a substrate for veneer, laminate and paint. Many wood working/furniture companies had problems with telegraphing of the particleboard core material when they used thin veneers with a high sheen. This was solved with the use of MDF.
While Sophie's problems could be atributited to a number of problems, veneer too thick, bad batch of MDF, etc, MDF is one of the best substraies to use for veneer. The company that I work for uses hundreds of thousands of board feet of MDF veneered stock every year without these types of problems.We are the people our parents warned us about. J. Buffett
I stand corrected but have to tell you that I thank God everyday I don't know poop about MDF.
Sophie,
Interestingly enough there just appeared an article on the Fine Woodworking
Homepage about MDF for veneers.
I'm sure you noticed but it should be interesting to read.
Tom
What about L/W MDF? Is it also intended to be used as veneer substrate or something else altogether? I use it for utility and throw-away projects like sets for the Children's church musical because it saves me busting my gut handling it. I haven't done any sort of veneering and probably won't, just curious. John O'Connell - JKO Handcrafted Woodworking
Life is tough. It's tougher if you're stupid - John Wayne
This forum post is now archived. Commenting has been disabled