the rot doctor


Subject: layup and laminating resin
Date: Mon, 23 Feb 1998

Dear Dr. Rot:

I received the layup and laminating resin that you sent to me, and conducted some tests. The viscosity and long cure time seem to make this product ideal for my purposes. At the moment, I am attempting to repair a bridge in a piano. The bridge is fabricated from clear maple.

My testing revealed that this stuff has an amazing ability to penetrate and fill deep cracks, and will even penetrate into the grain of the wood itself. Bond strength exceeded the strength of the wood itself, except in one case, where I had glued two smooth samples of maple together. In this case, the bond, rather than the wood, failed when broken apart. All my samples had at least three days to cure at room temperature.

A test with a freshly split maple sample showed good results, presumably because of the resin penetrating the wood fibres and forming a more "mechanical" bond. When broken, the wood, rather than the bond, failed.

The backside of instruction sheet packed with the product (sixth paragraph) seems to indicate that this product is not appropriate for hardwoods. I was not aware of this from either the information on your website or our e-mail correspondence.

Is this indeed true? Need I worry about these "saps and resins" in a piece of wood that has been out of the kiln for fifty years? Should I be using something else? I suspect that All Wood or Tropical Epoxy may be too viscous for my application.

Thank you for your continued advice on this.

-Kevin N.
Fulton, New York


Again, thanks for your kind comments about our Layup & Laminating Resin. You testing was conclusive and just the kind of final product work epoxy manufacturers do. Very good.

I did check with our technical people just to be sure I am correct. The problem with the failure on the smooth maple samples is that the resin just doesn't get the *penetration* you are seeing on the other samples. They believe and I agree that in cases where you are gluing smooth pieces together and the issue of crack penetration is not so big an issue, use our Tropical Hardwood Epoxy Adhesive. This has about twice the viscosity of the Layup & Laminating Resin. There would be no problem if the two products co-mingling at joints, etc. I don't think you would find a smooth joint failure with the THA.

The backside of the product literature says what it does about Layup & Laminating Resin and hardwoods because we want to guarantee -- as much as we can, anyway -- that what our customers are using is going to work for them, and when they buy the resin we often have no way of knowing exactly how they are going to use it or what they are going to use it on. The simple truth is most epoxy resins will fail at least part of the time on hardwoods. With our Layup & Laminating Resin you are using a superior-grade resin under ideal conditions and in circumstances that while strength is required it is not the same kind of tremendous sheer and compression strengths required in marine and aircraft construction. So the bottom line here for you is if the Layup & Laminating Resin is working for you, by all means continue to use it. Consider using our Tropical Hardwood Adhesive on the smooth surfaces.

You are correct about the saps and resins -- they are not an issue in a hardwood as old as what you're working with.

Get back to me Kevin if you have more questions.