Decal Delaminating from Epoxy Finish

      Troubleshooting a situation where a decal on a wood table is lifting under the epoxy finish. March 13, 2014

Question
WOODWEB Member:
I made a coffee table and two end tables out of eastern white pine slabs a few years ago. The customer wanted Harley Davidson logo decals on each table. Now for some reason, I think expansion and contraction, the decals on the end tables are lifting up through the 1/8" thick epoxy coating. I now have to repair it which can't be too difficult because it just has to be sanded and recoated, but what will stop this from happening again?

Forum Responses
(WOODnetWORK Forum)
From contributor G:
I think first we need to know:
How dry were the slabs?
Are they real decals (soak in water, slide onto surface) or were they plastic self-adhesive sheets?
Does the underside of the slab have the same 1/8 inch finish?
Is the failure between the wood and the decal or is the epoxy lifting off the decal?



From the original questioner:
They dried for a year outside. I got them right from the mill. I didn't check the humidity. The decals were self-adhesive and not soaked in water. The underside of the table was lacquered with 3 coats of pre-cat top coat. The failure seems to be between the wood and decal but the decal is moving and folding.


From contributor G:
I am having trouble with this one. Obviously the adhesive on the sticker is the weak point. The epoxy sticks to the top of the sticker (and to the wood) but the sticker glue has (or is) failing to maintain a bond to the wood... but you know all that already!

Those pour on two part polyester table top finishes; the ones that look like they are a quarter inch thick are often used to embed paper things in the finish (decoupage). In that method the wood is first given a thin layer and the paper items are put on top as the lower coat while it is still wet, then it is given the heavier top coat. That way the graphic material is in the finish and not under the finish. I suppose if both sides of the sticker see the same material and the top of the wood sees only the coating, then nothing can move.

With your deal however, if you let the first coat dry, put the self-adhesive sticker on, and then top coat, you still have one side of the sticker seeing epoxy and the other seeing what is probably a latex (rubber) cement self stick material, which I am guessing over time has very little grab compared to the epoxy.

Can you get the graphics without the peel and stick feature? Could you copy them onto paper or plastic film which would have no self stick stuff? I am thinking that if you put the paper or plastic film on top of a wet layer of your finish - maybe even spray a spritz coat on the back of the graphics at the same time to get a good wet to wet bond between the graphic and the underlayer, then top coat according to the finishes recommendation, that the graphics would be buried in the finish and would be better behaved.

I considered if your wood was too moist, but since you have it coated both top and bottom, and since the epoxy is sticking by itself this probably not the problem. Also if the wood is fully encased in epoxy it is not changing its moisture level much at all, so the wood is not moving.

Hope that helps some. I would try a test panel with non-self-stick graphics embedded in the finish. (After it is dry, try a few days in the sun, and then a day in a really warm environment as an accelerated aging test to see if that method is stable.) If that doesn't, then try the pour on two part finish stuff with non-self-adhesive paper graphics. That will work except you don't get as hard a finish, although I have seen it used in plenty of restaurants.



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