Did a stock with Helmsman poly spar varnish. Two days later, a t-shirt pad left weave marks in the finish, with light pressure in a leather padded vise. Can I speed up the hardening? I know spar is softer than regular. Will a shot of oxygen from my welding tank inside a big baggie do it? Or is heat or UV light an accelerant to the curing??

Most manufacturers formulate their Spar Varnish with linseed oil and Tung Oil. The larger the portion of Tung Oil, the better quality of Spar Varnish. Other companies choose to put more linseed oil in their formulations, primarily to lower the cost. Tung Oil is about four times more expensive than linseed oil. However, linseed oil is an inferior oil for Spar Varnish
linseed oil completely deteriorates causing the finish to breakdown. Additionally, linseed oil's drying and curing time is very long. The increased dry and cure time allows moisture to remain between coats which eventually permits competing products to crack and peel and stops protecting the wood surface. Linseed oil has no waterproofing properties. over time, linseed oil turns a wood finish very dark, almost black
I use truoil with a stain added or thinner.
It doesn't work real good if you try putting a poly finish over it.

Lanny,

Through experience I have found the fastest AND SAFEST way to dry poly is to get warm, dry, moving air to it for as long as possible. With direct heat you run the risk of air bubbles popping up through the finish.

Jim