: I just finished sanded (320 Grit) a test panel (Bulkhead) and when I did a
: first varnish coat I noticed small pits in the weave that must not have
: filled level or sanded level on the fill coats for one reason or another.
: These pits didn't appear noticeable until the varnish went on. Will these
: pits fill in smooth with varnish or should I sand the varnish off and do
: another fill coat?

This sounds like a classic example of "off gassing" of the wood during coating. If the temperature is rising during seal coat/glassing of the wood air in the wood cells expands and blows holes in the resin. IF on the other hand you coat during falling temperatures resin will be sucked into the wood cells with contracting air. One coat of resin may not seal all wood cells so it is prudent to ensure your shop temperature is dropping during the second coat or glass wet-out.

Once you have these pin holes they can be very difficult to get ride of. I'd suggest sanding back to resin and remove as many pin holes as possible by sanding. Then recoat WITH FALLING TEMPERATURE to use the contracting air in the wood cells to pull the resin in and fill the holes.

Be glad you learned about "off gassing" on a small panel instead of on your boat hull or deck.

The other possible cause of the pin holes is squeegeeing multiple layers of glass during wet-out. Epoxy resin has no tack strength (stickiness) whatsoever, so if you try to press glass flat and remove excess resin with a squeegee the glass will spring back, every so slightly, like a sponge and pull resin or air into the weave. When you do a good job of squeegeeing off excess resin, that's why the surface will have such a uniform "matte" look to it. However, if you wet-out two layers of glass at the same time and squeegee off excess resin there is a bigger cushion of resin and glass to work out excess resin from during squeegeeing.

Every time I've wet-out two layers of glass at the same time I've ended up with air bubbles or pin holes.

All the best,

Rob Macks
Laughing Loon CC&K
www.LaughingLoon.com