: HELP! After my second coat of varnish (z-spar captains)air bubbles have
: appeared.I wet sanded inbetween coats with 400 grit.The boat is epoxied
: with west system epoxy that has been cured for 2 weeks.I used a new badger
: hair brush for the application of the varnish.This is the same way I
: varnished a kayak I built last year but had much better success. Could it
: be bad varnish or too hot 80/90 degrees F. TIA Don

Hi Don,

Are these air bubbles or solvent popping? Solvent popping is caused when the surface of the varnish skins over before the solvents below have evaporated out. It is usually a result of applying the varnish too thick, either in one coat or in applying multiple coats before the first coats have flashed off.

The temperature will have an effect on solvent popping but it usually just aggravates an existing problem. You could check the instructions with the varnish and see what they recommend for various temperatures. Usually they will alter the amount of solvent or replace it with a slower drying solvent. The solvents are more to do with allowing the product to flow out better at different temperatures.

I would say that you are probably putting too much material on in one coat. Go with less material but more coats.

You do not have to sand between coats. You can apply three coats wet on wet as per the manufacturer's instructions. (check the flash time between coats) Allow these to dry and sand them before applying more.

This was the old way of achieving high gloss finishes with laquer. You applied three coats, allowed them to dry, wet sand. Apply three more coats, allow to dry, wet sand. Etc. Until the desired results were achieved. The final coats were sanded with ultra-fine paper (2000 grit) and then polished to restore the shine. Laquers being thermal-plastic (as opposed to thermal-set) would actually reflow with the heat of the polishing process.

Keep in mind that 3 thin coats, with proper flash time between, is far better than one thick coat. The film built will be the same so you will get the same protection but the finish is much nicer.

Ian