Vacuum using epoxy with veneer

[Craig Beck]

I'm new to veneering and plan to veneer birds eye maple to steel for parts on an auto dashboard. I live in Texas, so it will be subject to high heat and humidity. From what I've read, epoxy seems to be the choice of many (although not all) for this type of dissimilar combination. However, the readings also indicate that if any joint is pressed together too tightly, the epoxy is squeezed out causing a dry joint that doesn't stay bonded. I've been building experimental composite aircraft for many years so have a fair amount of experience bonding fiberglass to foam with epoxy. For some applications, we use vacuum to draw unnecessary epoxy out, but we only use 11 inHg so that the pressure doesn't crush the foam. To reduce the probability of creating too much pressure and draw too much epoxy from the bond between the maple and the steel, would it make sense to reduce the vacuum from the normal 18 - 21 inHg used in bonding veneer and wood to something near 10 inHg, or even less?

Second question, has anyone used West's relatively new GFlex epoxy to bond veneer and steel?

[John TenEyck]

I recently vacuum bonded some veneer to Melamine with epoxy. I ran the vacuum pump at the 20 - 22" Hg I normally use. I didn't see any glue squeeze out at the edges. It's been about 4 or 5 months now and everything is fine. A perfect vacuum is only 14.7 psi and 20" is only about 75% of that; it's not a lot of pressure. I think epoxy is a good choice for your application and you should get good results at normal vacuum levels. But if you want to run at lower vacuum a dry run would be in order to determine the minimum vacuum level needed to assure the veneer conforms to the substrate.

John

[Larry Copas]

I've been using GFlex for a couple of years now. I have bonded shop sawn veneer to aluminum plate and also knife scales to the knife. I actually bought it to install an under mount stainless steel sink into a laminate countertop. I wanted a flexible but watertight bond. It has preformed perfect in all applications, even some routine glue ups.

If I have any questions about West products I call there engineering department. They have always steered me straight, even suggesting a competitors product if it would be the best solution. They are a great company.

[Craig Beck]

Thanks for the help

[Mike Henderson]

I don't think it's possible, with a vacuum press, to squeeze a joint "dry" - to the point where the veneer won't adhere. A portion of the glue will go into the wood and that will give you adhesion. The only time I ever had bubbles in veneer (lack of adhesion) was when I didn't put enough glue on the substrate.

One problem with epoxy is that it can come through the veneer and show after you apply the finish. So you need to use enough glue, but not too much. I think some people use backed veneer to avoid that problem.

Mike

[Peter Quinn]

Maple is fairly closed grained, the birds eye aspect may be more open than some, perhaps a thickner might help solve both the squeeze issue and the bleed through issue. West systems sells a number of fillers as part of their system, perhaps the 406 silica based filler might be a decent color match for maple?