Thin Epoxy

[Delwin D Fandrich]

----- Original Message -----
From: "Farrell" <mfarrel2@tampabay.rr.com>
To: <pianotech@ptg.org>
Sent: February 26, 2003 7:54 PM
Subject: Thin Epoxy


> I ran across this site and thought of Del and Ron N. and Ron O. They are
out by Del. The topic of low viscosity epoxies has come up on the list
often.
>
>   http://www.rotdoctor.com/products/product.html
>
> A couple very interesting products:
>
> -    CPEST (Clear Penetrating Epoxy Sealer)
> -    Tropical Hardwood Epoxy AdhesiveT
>
> The sealer is said to be of diesel fuel viscosity and penetrates into wood
way more than other epoxies (laminating bridge caps - your soundboard
coating thing). They also claim that WestSystem is petroleum based and cures
brittle (I certainly agree that it is brittle).They say their epoxy is wood
based and cures flexible. I'm not sure exactly how that might benefit/effect
our work on pianos, but there it is (in a bridge cap, I don't see where it
would make much difference - brittle or flexible). The penetrating sealer
really gets my interest. Hmmm. Maybe we can laminate a thin strip of Kevlar
into those bridge caps and use this penetrating sealer for the ultimate
bridge cap - 'course it might be a bit of work to get a pin in it and to
notch it.
------------------------------------------------------


I am aware of this product, but have not used it. I've been just a bit
apprehensive, mostly because I consider the advertising and promotion, along
with the so-called comparison tests, to be just a little bit misleading.
Basically, CPEST is a solvent-thinned epoxy resin. The major difference
between this and other standard structural epoxies is that CPEST is supplied
pre-thinned. In these 'tests' only its penetrating capability, not its
structural strength, is being compared, yet the other standard,
multi-purpose coating and penetrating epoxies have not been thinned to
anywhere close to the viscosity of CPEST. I suspect that if the other
epoxies had been thinned out with their appropriate solvents to the same
viscosity as CPEST they would have penetrated much better than is indicated
in this test. They would also loose some of their structural strength, as
does, I suspect, Dr Rot. But this characteristic is not tested. You may
notice that CPEST is not really being marketed as a structural epoxy while
the others are. In terms of flexibility, if structural epoxies such as WEST
System or System Three structural epoxies significantly they cure to a
somewhat more flexible state as well.

So, what have we? I suspect that CPEST is a basic structural epoxy thinned
with whatever thinners are appropriate for the resin/hardener system and
sold as a thin, penetrating epoxy sealer that is "strong." Before becoming a
believer I would like to read an independent analysis of the material.

Besides, in the soundboard work I've been doing I don't want the kind of
penetration being described by Dr Rot. These boards are not rotten, they are
structurally and stiffness impaired. I want all of the structural strength
and stiffness I can get. O.K., within reason.

Del