Veneer Checking on Architectural Columns

      Movement of the veneer (attached using contact cement) is the likely culprit in this failure. September 16, 2008

Question
I did a job for a client in pre-cat lacquer. Itís a wood veneer on two columns 20' high about 3' diameter with a reception desk. All the veneer is checking. How can I fix the problem and the finish onsite?

Forum Responses
(Finishing Forum)
From contributor C:
Contact cement?



From contributor A:
What is the wood species and type? As in, is it a crotch or burl or highly figured? Was the temperature, and humidity stable before during and after layup and is it consistent environmental in the current location? Is the current environmental similar to the conditions during manufacturing? Itís difficult to answer your question without this background info as a start.


From contributor A:
On a second look, it is unlikely that 20'x3' columns are crotch or burl? What is the wood species and did you re-finish or was it ready to finish for you and are you certain that the veneer is checking?

It seems unlikely that a finish pre-cat or otherwise would cause any type of veneer to check. Something else is going on. Try to provide more info and maybe something will make sense.



From contributor M:
You will first have to decide if it is really the veneer "checking" or the finish shattering. Some pre-cat lacquers can shatter (looks just like shattered glass in a car window) if the dry film thickness is exceeded. Get a cheap 100x magnifier from Radio Shack and scrape away some finish from a bad area. After the finish is removed look at the veneer with the magnifier. If you can no longer see the checks it is a finish problem if the checks are in the veneer then it is a glue problem. (These weren't glued up with contact cement were they)? Let us know what you find out.


From contributor J:
To answer your question, the only way to fix the problem, is to strip off the old finish, iron everything down, and finish it again. I had the same thing happen to a huge wall unit that was white oak. It was contact cemented on white melamine and then after it was finished it was left out in 10 degree weather for three days, then brought into an 85 degree Manhattan apartment.


From the original questioner:
The veneer used was carpathium elm. It was glued up using contact cement and was done in Las Vegas NV during the winter.

The shop that laid up the veneer on MDF was probably no warmer than 60 degrees. My shop where we finished was about 65-70 degrees. It was installed in a new building probably about the same temp until heat and air was turned on.

Itís in the front of the building that is all glass so the temp changes. It is cracking vertically, not like glass. I have seen this before when the mil thickness is too much or too much caty added to the product.



From contributor A:
First thoughts are; if this is a true carpathian elm (French), then you are dealing with a species with little bending properties. It holds up quite well to water yet does not steam bend all that well. Much is dependent on the mil thickness of the veneer and how they laid it up. Since there is no cracking pattern following a burl or eye pattern but instead a vertical crack I would lean toward the radius bending (degrees and/or process) being the cause. Be it the mil thickness (of the veneer), (in this case the thicker the worse the cracking would be), the mfg process and adhesive chosen as all possible parts of the problem. Now, on top of that throw at it an environmental change of +/- 40 degrees fast and frequent and you are seeing exactly what I would expect.

Can you find out the mil thickness of the veneer? No matter what it is I don't know who is going to be responsible for this one unless there is one point person who spec'd this project without taking all these things into account. Wood moves, shift happens, and the finish will crack also. There may be some answers to fix this but more info is still needed or time and effort is just going to be wasted.



From contributor C:
Cracks with grain are a glue/manufacture problem. Broken glass look is a cold check and a finish problem. Contact cement will always move, after all it was designed as a shoe makerís glue.


From contributor R:
The fault does not lay in the hands of the finisher for this problem. Contact cement should not have been used for laying up this veneer. It would not matter the finish that was applied for it would have eventually cracked one way or another. The fact that you used a pre-cat instead of a varnish instead of a 2KPoly makes no difference.

I donít think it even makes a difference if itís a true or genuine carpathian elm. It shouldnít have been laid up using a contact type cement as the glue. I donít see the advantage of stripping and refinishing the elm as the finish is not the problem, itís the type of adhesive that was used.

Also the fact that a vertical surface like a desk has a cracking issue eliminates the radius glue up as being an issue. Contact cement might be fine for applying a wood veneer to the edges of a door or drawer front but not for large surfaces such as you have alluded to.



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