Troubleshooting Veneer Failure on MDF

Contact cement is the culprit in a veneer bubbling incident. Rx: re-do with the right glue. April 21, 2008

Question
We used 3 layers of 1/4 MDF to form panels in a 20 foot diameter x 20 foot ht lobby. We used contact cement to glue the qaurtersawn oak custom veneer to the MDF. The project was sprayed with c144-15 then installed on site. 9 months later, after 3 weeks of rain, our customer called to say the veneer is bubbling. We went to the site to see the problem and it was bad. Most of the panels had bubbling on the entire surface, and it seemed mostly on the large flecks of the grain pattern. Why did this happen and how do we fix it and prevent it from happening in the future? Also, who is fully at fault?

Forum Responses
(Veneer Forum)
From contributor R:
To answer your last question first, you are at fault here. Contact cement is the last thing you want to use when laminating wood veneer to any substrate. Wood, be it veneer or solid, is porous. So when you spray your finish on your panel, it bleeds through and starts to break the contact cement down. It may not be noticeable at first, but with time and the constant movement of your veneer and substrate, something has to give, and in this case it's your veneer. The flakes in the veneer where it's happening the worst is due to the fact that in these areas the veneer is very thin - you can almost see through it. Whenever you glue veneer to any substrate, you have to use a PVA or a urea type of glue in order to create a strong bond between the two surfaces. After the glue dries and hardens, it creates a barrier between your substrate and veneer that holds the two together and helps to limit the movement between the two. It also holds up very well to most finishes and solvents. Contact cement is good for p-lam and that's about it. I will also add that it happened after it rained probably because of high humidity in the air and, again, wood is porous and is like a sponge, so as it absorbs moisture, it swells and causes the veneer to break away from the contact cement. There is no way to fix this problem other than to take the panels back to your shop and re-fabricate them with the right glue.


From contributor D:
Try using bubble-free veneer. You can get it at Oakwoodveneer.com. It has layers behind the wood that prevent the lacquer from seeping through and ruining the glue. I had the same problem as you a few years back and found this stuff. It's great for contact cement applications.

From contributor C:
Despite what the well-intentioned but inexperienced will say, don't ever, ever, ever use contact cement for any type of veneer work.

From contributor P:
If I read your post right, you say you glued 3 layers of 1/4 MDF together. I assume these are up against a curved wall. Thus a 10ft rad? What did you glue those together with? If you use contact cement, you are still in the wrong there as well. I hate to say it, but you will probably end up having to remake the whole thing, pressing the entire panels with the correct glue. The MDF is fine unless it is a humid environment, then you will need to finish the backside as well to control the moisture and balance the panel. How much work of this type have you done before?

From contributor N:
I’ve recently used exterior grade MDF for a veneering project and it holds up great. I’ve also done a test on it. Soaked a 1-inch thick piece in the water overnight. The expansion was like 0.002. Fixing bubbles on contact cement successfully is impossible. I think the least expensive way would be to bring this thing back to the shop, rip the veneer off, clean off contact cement, and redo it in the vacuum bag, preferably with Unibond 800 or such. That depends on the condition of the MDF itself. Any type of exterior or semi-exterior woodwork calls for a durable finish. I like 2k urethane. Encase the piece in the finish and it will be fine even if the building is submerged underwater.
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