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Re: Epoxy finish
By:Paul Jacobson
Date: 4/24/1999, 8:39 pm
In Response To: Epoxy finish (Don Price)

> I have just finished putting a second layer of west system and I still
> have a rough surface. The cloth has wet out real good in that it is clear
> and there are no white spots or air bubbles.I am going to put 2 more
> layers on tonight in 3 hour intervals.Will these next to coats smooth out
> the finish or will I have to smooth it out sanding when fully cured? I
> used 207 hardner and the finish is real clear.I don't want to screw up
> now. thanks Don

Either knock down some of the roughness by sanding now, or put on just one coat tonight , sand, and then put on the fourth coat (if needed) at a later time.

The first coat of resin tends to soak into the wood, leaving the surface of the cloth exposed. Actually, a lot of resin really is on the surface of the fabric, and you don't have exposed glass fibers. What has happened is that the resin that is in the intersections of the woven bundles of fibers -- where one goes up as the crossing one goes under -- drains away and soaks into the wood, crating many tiny `pits' or `wells` at these points. The second coat of resin may, or may not, be thick enough to flood over the cloth and totally conceal the weave, by filling these pits. Of course, the second coat does not just fill those pits, it also adds a layer of resin to the resin already on top of the glass fibers. Now the fibers have two coats of resin, and the pits, or wells, in the weave are not as deep.

At this point, if you put on another coat of resin it tends to coat the high and low spots pretty evenly. A bit will drain into those wells, but a lot stays on to+p of the (now buried) glass. This is where you get the effect known as `telegraphing' the weave. Adding more thin, even coats of resin gets a thicker layer of plastic overall, but the pattern tends to keep reproducing itself.

The problem here is that if you put the second coat of resin on thick enough to completely fill the wells, and level off with the high spots from the first layer of resin, it tends to run. The solution seems to have two components: Sanding and thin coats of resin -- sometimes you put on two and sometimes you put on three thin coats. A light sanding between coats, with a fine or medium sandpaper, takes off the peaks of resin, effectively giving you shallower wells to fill. You do such a light job of sanding that you don't need an electric sander for this job. A simple sanding block -- a piece of sandpaper wrapped around a scrap of wood -- is sufficient. One or two swipes with this over the whole area kills the glossy look (which means you are knocking the highspots down) but does not go through to the fibers of the cloth. If you haver runs. by the way, this is a sure way to see them. You might as well get rid of those at this time.

The less resin you put on, the less the boat weighs. Once the cloth is completely covered by resin any additional resin adds no significant strength or ding resistance, it just adds weight. If you don't need a fourth coat of resin, don't put one on. Finish up with varnish instead.

Hope this helps

Paul Jacobson

Messages In This Thread

Epoxy finish
Don Price -- 4/24/1999, 7:17 pm
Re: Epoxy finish
Paul Jacobson -- 4/24/1999, 8:39 pm
Re: Epoxy finish
Byron Lawrence -- 4/26/1999, 2:27 pm
Re: Epoxy finish
Shawn Baker -- 4/24/1999, 11:30 pm