I thought this section might be different from the others, but after trying to post, I realize I still have to check the "professional" box, which I'm not. Not knowing where else to ask, yet, I'll send this futile question into the ether, anyway. Bought a can of spar varnish, that was older (last one on the shelf at ACE, so....). I thought I stirred it well, but 1st coat just won't dry. Apparent progress turned out to be harder at night, then softening in heat. A test piece after extended mixing dried normally. Normally, I'd steel wool and second coat this top, wondering what options I've got. Could I consider the uncured varnish something that would kick off with a new, well-stirred coat, without buffing between? If I wait for weeks (already 2, some progress, but still slightly tacky), will it eventually cure? Should I hit it with paint thinner and scraper and try to get it down to something that'll dry? Chart cabinet destined for decorative, no real sweat about future weather. Thx.

You got the "professionals" notation because this is a forum for true professionals. A lot of detailed technique and business acumen is passed between members.

However your inquiry fits right in and there is no reason not to respond.

I'd pick up some Japan Drier. You can get that at most any paint store. Dampen a rag with it and lightly rub it over the existing finish. Try it first in an inconspicuous corner.

The softening problem you are having is common enough with old oil varnish. Mixing in a cap full of Japan Drier per gallon usually solves the problem. I have some decades old oil varnish that I keep around for an occasional small project. You can't get it any more and it was a good product. But........I don't use it for architectural items as it will soften in high heat just as you are experiencing.

BH Davis

I have done Fine Art professionally and have been refinishing wood and painting my entire life. I recently decided to refinish an old oak floor. After preliminary sanding, I applied Minwax penetrating stain. I then applied a coat of traditional spar varnish to half of the floor. After three days the varnish would not dry at all. We are experiencing summer days of interminably high humidity and daily thunderstorms. Since I don't have until winter to wait for this varnish to dry, I determined to find a correction for it. I tried brushing small segments with lacquer thinner, which is a blend of solvents. That helped some, but it a stronger solution was needed. Having occasionally worked with Formby's Furniture Refinisher, I was familiar with the concept. The Formby's product contains MEK, which which is in the same chemical family as paint remover. MEK is extremely volatile and evaporates quickly. In adding a very small amount of MEK to a container of lacquer thinner I was able to duplicate the effect. The process involves removing most of the varnish but leaving behind a very thin coat of it, which is then no longer tacky to touch. This correction will work but it is a laborious process. If working indoors, wearing rubber gloves, running a large fan and opening all the windows of the room is an absolute necessity. Use a metal or glass container for the solution. Apply it to a small section of the wood with a 1-inch brush. Wipe off the mostly dissolved varnish with a clean rag. The rags will become laden with varnish and solvent; let them dry and dispose of them properly. This process solved the problem. I now plan on buying some Japan Drier and adding it to my varnish, then testing it in a small area before proceeding with this refinishing job.