Contact Cement and Bubbles Under Veneer
A report of veneer delaminating from architectural columns leads to a long string of cautions about using contact cement to apply veneer, along with advice about superior methods. March 4, 2007
Question
Veneer (cross-banded wood backer) was applied to columns with contact adhesive approximately 18 months ago. Small bubbles developed approximately 4 months after install and have been slowly growing worse since. Looking for possible causes of this problem so we can avoid it going forward.
Forum Responses
(Architectural Woodworking Forum)
From contributor M:
Where do your installed columns sit as they relate to exposure to direct sunlight, or heating sources like forced air vents or radiators? I've had contact cement delaminate when placed under direct sunlight (black hp laminate on a piece that was sitting outside my workshop on a sunny day!) and had this problem once in an old house when the finished piece was fairly close to a steam radiator.
From contributor F:
Yes, heat can definitely cause delamination. Also, I have heard that when using waterbased contact cement such as 3M Fast Bond 30, if too heavy of a coat is applied, it can dry on the surface but still be wet underneath and cause delamination later on.
From the original questioner:
Thanks for your responses. Some of the columns are exposed to sunlight - others are not. Some have adjacent HVAC vents - others do not. The columns that are not exposed to the sunlight or vents are delaminating the same way as the others. Veneer was applied to the columns (approximately 36" diameter, 96" tall) at the jobsite. We believe the contact adhesive was sprayed using a portable tank. The veneer was finished after field application.
From contributor D:
Someone needs to say that you should not use contact cement for veneer. Convenient, yes; long lasting, workable, reliable, no. I would say that veneer and contact should never be used for quality work. Use proper glue - urea resin is one good solution - get a rigid glue line, and you'll have no problems, sun or otherwise. Do a quick search on veneer glue and you'll see the good, bad and the ugly.
From contributor F:
I was tempted to say what contributor D said as well. Pressing veneer tightly to a circular surface while using proper veneer adhesives is no easy task, though. Another good way would be to use hot hide glue. Veneering circular surfaces with hammer veneering techniques will make fitting the seam much easier.
From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Check the archives for more info. One good discussion in the past is at the link below.
Veneering with Contact Cement
From contributor E:
Aside from the fact that contact cement and veneer is suicide looking for a place to be committed… Is the column concrete?
From the original questioner:
Not entirely sure of the column material - we think it may be fiberglass. That is being checked on. It may be a gypsum blend product. Thanks for your comments.
From contributor D:
My personal first experience with contact and veneer goes back many years. I quoted a panel law office with sequence match walnut, stile and rail. That was too expensive, so they wanted "contemporary" with no stiles and rails, as an attempt to save money. They still thought too high.
They found someone to lay Jacaranda product on the drywall with contact cement, and laid it on, rolled it, and sat back and passed around the congratulations. They were unaware they violated a basic rule: If you have never seen it done it before, there is a reason.
The finishers came in the next day and did the usual fog job with the lacquer. Within 30 minutes, the corners of the veneer sheets started curling and pulling away from the alleged "substrate." They tried taping the corners, propping edges up with loose moldings - it all failed. Then they came back to me and tried to fault our shop for not warning them...
There is a real problem that some manufacturers of sheet veneer suggest contact as an acceptable adhesive for their product. This is purely in the interest of increasing sales to the unaware. Such recommendations are irresponsible and definitely hurt the practice of our trade.
From contributor E:
The appropriate Jacaranda product for wall covering is sold as "Sanfoot" and the installation instructions specifically state that the installation be done by a commercial installer with 3 or more years experience and with a waterbased polymer emulsion adhesive and adhesive brand names are mentioned in the instruction. Only the brand label/name has changed over the years to keep current with commercially available labels. The Sanfoot product is also factory pre-finished to meet class A fire code requirements. Completely different product from the two ply veneer in this thread, on one hand, and someone must not have consulted with Jacaranda for proper product selection, on the other hand.
Again, contact cement is an exception where wood veneer is concerned.
From contributor E:
If it should turn out that the columns are concrete, the bad news is that they may need to have a barrier added and that is spelled r-e-w-o-r-k. I'd start with a moisture check of the substrate, concrete or otherwise, if you can get access to the substrate. The MC of the 2 ply is less of an issue at the moment.
From contributor H:
Next time try phenolic-backed veneer. Lacquer or any other finish will not effect it. Works well with contact cement or silicone adhesive.
From contributor C:
I would estimate that in the last 15 years, we have made over 20,000 veneer wrapped cylinders of all sizes. We started using contact cement and quickly learned that delamination and bubbles were often the result. We used a fiberboard core and tried everything from glue sizing to heating and re-rolling. We never had a bond quality that we could stand behind.
After a month of that, we went to a spl PVA glue and have never looked back. Unfortunately, we have used clamps and have made special cylinder presses that used air cylinders and heat to cure the adhesive. A very expensive line of machines, but the results are 99.99% perfect.
There are occasions where we have to use a contact cement and in those cases, we lay up a 3/32" thick bendable plywood and use a contact cement with white glue at all the edges. This works very well for large diameters, greater than 42", where there is not a lot of bend resistance.
In your situation, a 3-ply of some sort may have worked, but you should take a look at the stability of the core material. If a core is porous, it may be sucking the glue dry. One possible way to do this would be to use a thin plywood substrate over the core with a permanent adhesive. That way, you could do whatever it takes to get the first ply to adhere, i.e. cut it open, add glue, band clamp it, iron it to dry, etc. Sand the wood substrate and glue size it, then use the contact adhesive.
