Troubleshooting Veneer Lifting and Gaps

Pros tried to figure out what caused the problems with a bad batch of veneered panels. March 31, 2008

We purchased veneered panels from an outside source. During production the veneers looked okay until we started finishing. In some there is this unsightly gap about 2mm wide between the joints. In others, they are lifting or raised at the joints. Quite a lot of this is happening and all the units have been fully built. I cannot redo this anymore, as my delivery is overdue. What is the cause of the raised joint and gaps in the joints? How can I repair the situation when I have already fully assembled the items?

Forum Responses
(Veneer Forum)
From contributor J:
Have you called your supplier about this? They should at the very least be willing to troubleshoot this with you, as they will know what kind of glue they used, etc.

If they used a regular PVA and the veneer has dried and shrunk, you might be able to re-expand it and stick it down with a clothes iron and some water. Maybe they could lay up a two-ply from the same flitch that you could contact cement (can't believe these words are coming out of my... er... fingers) over the trouble areas. In any case, if it's a problem with the layup, they should be supporting you.

From contributor E:
Sounds like your supplier may have used PVA glue. Is the veneer maple? Maple is bad about doing this with PVA glue. A 2mm gap is really bad; a slight gap can be filled when finishing, but this sounds like it may have to be routed out and glue in a filler strip. If it's not possible to get an invisible match, you might want to consider making the fill obvious, as in a contrasting infill. At any rate, your supplier should accept responsibility for this and correct the situation.

From contributor R:
Been using PVA glue for years. Never had a problem with it other than pre-cure before it went in the press. There are a number of reasons why this may have occurred. If it's maple and they used either tape or a stitcher to fabricate the faces, there's the beginning of your gap problem. Maple is notorious for shrinking in a hot press. When you edge glue the veneer and fabricate it through a Diel splicer or some comparable machine, you greatly reduce the chance of this happening. Reason: you're gluing the joints together the same way you would glue two pieces of lumber together, therefore creating a joint that is stronger than the wood itself. When the maple face shrinks during the hot press process, the edge glue in the seams holds. On the other hand, if the faces were made with the old Kuper type stitch, especially with maple, you're doomed from the start. This type of splice line has no holding strength whatsoever. So this is one type of possibility that could have caused this.

Another possibility is the pressing process itself. Too much glue causes lifting at the seams, which may not be immediately noticeable when it comes out. Not enough time in the press is another culprit, as is the wrong heat range. My guess is the faces were Kuper stitched, the veneer was at a high moisture content, and what you have is a delayed de-lam problem. Saw it many times years ago when I first started doing this. When I make faces they are always edge glued with Borden DS-200 run through a Kuper FL/Innovation splicer and pressed at 205 degrees Fahrenheit for 2 minutes at the appropriate pressure, with a PVA glue provided by National Casein. Have pressed thousands of panels over the years with great success. Your panel manufacturer seems to be totally at fault here. Substandard work.

From contributor D:
As a veneer press specialist, might I ask you a few questions before answering.
1) What is the veneer species?
2) How thick is the veneer?
3) What method did your supplier use to pre-cut the veneer?
4) What method (very important) did your supplier use to seam the veneer together to produce the face?
5) What adhesive was used to press the veneer?
6) What type of panel was the veneer pressed onto (PB, MDF, ply, etc.)
7) How was the veneer pressed onto the panel? (hot, cold, vacuum bag)

From contributor C:
All of the suggestions for why your panels crapped out are correct. But this should be an issue for your supplier to figure out. Did you have these custom made or are they stock 4 x 8's? We do thousands of panels a month and find that any time someone overlooks a basic rule, it shows up later. We now follow proven guidelines like robots, and have very few problems. These days, lots of guys are buying little presses and zig zag splicers. But there is more to getting a tight face, flat panel and check free product than you would think. Rules for one wood do not apply to other woods. We do flk, MDF, ply and lumber core, all of which require different approaches.

From the original questioner:
Thanks for all your advice. It is true, different veneers and substrates have special needs. We are currently doing tests on the Geronggang veneer specie we are using. I had to initiate the testing and seek all your kind advice and am taking from here.

I would like to share the remedy we undertook. Having completed finishing when this situation popped up, we washed off the finish with acetone. Then we applied super glue to all (as in all) the seam lines. We let this set then sanded it down flush. It filled the gaps well enough and we hope it holds over time. We finished it again, making adjustments to the stain as we all know when we wash off the finish, there is stain that cannot be removed.

I know this is the problem of the veneer vendor, but having a close relationship with our supplier, we jumped in and are working out the problem together.

From contributor U:
Similar topic, different scenario. New table - after 3 months, can feel and see veneer lifting on surface. Does anyone have a website or technical reference book that they can refer me to for research purposes? Have more furniture of this line coming, and am concerned about a repeat occurrence.

From contributor E:
Take this up with your dealer or the manufacturer. They should take care of this for you. As for the other pieces, sometimes there are problems in the manufacturing process. I call them Friday afternoon pieces, where a mistake is made and the piece goes on past the inspectors and out the door. I would let the dealer know that if your other pieces have this problem you will demand a refund. Most reputable furniture dealers will work diligently to satisfy the customer. If your dealer will not work with you, call the manufacturer direct. If your piece is custom, consult with the furnituremaker.

From contributor E:
I responded above without thinking of the possibility that the veneer damage could be caused by the homeowner. The only thing that would cause this in such a short time would be overexposure to direct sun, heat or water on the surface from glasses and/or wet rags. If none of these apply, then I would go back to what I stated above.