: Correction

As per a Chemist friend of mine "Varnish will cure in depth as the oxygen from the air diffuses into the coating and reacts with the resin, catalyzed by the "through dryers" that are present. Varnish cures not-that-fast, and the hardness that develops does not indicate complete cure, as the areas beneath the surface are not fully cured where another fresh application can react even a couple of days later. I think in the Good Old Days, when LEAD was the only drier needed, the surface was tacky enough long enough that excessive airborne debris accumulated by the time another coat could be applied, necessitating sanding to clean it up. when cobalt was introduced as a top drier, its much greater reactivity led to a more fully cured outer film surface (dry-to-dust sooner), which gave poorer intercoat adhesion, thus again necessitating sanding for good adhesion unless the cobalt level was reduced considerably, which does not seem to be the case with most products. In the last ten or fifteen years modern gloss-enhancing additives have been developed, and they really destroy intercoat adhesion unless the drier levels are reduced so far that dirt accumulation is again a problem."

Therefore I think we are both correct, however I will continue to sand the epoxy with a coarser grit than between varnish coats.