I have some old Flex Coat, and the clear bottle of Varnish has hardened on the bottom. Can I still use the portion that is still liquid or is the whole bottle bad? What is the best way to store Flex Coat or any finish?

Cool, out of sun.
Take the top off the bottle of clear and microwave (don't want it to blow up in ma's m'wave) it in 10 second bursts until it's liquid again. Do this every 5 or 20 years as needed; never goes bad!! LOL

Putter

Randy, that works?

I have some large bottles where the resin has hardened into a brittle band across the surface about 1/4" thick. I've never had this happen to me before and as usual, have been overthinking the problem. I always have sticky bottles, even on ones I haven't opened and was think of a "cross contamination" of sorts where a little bit of hardener seeped into the resin and started to set up somehow.

The older I get, the less chances I like to take. Always been afraid of waving rod finish where I heat up my burritos!

The clear part of my rod finish has been nuked twice, maybe 3 times in the last 15 years. It sets up like beeswax towards the bottom of the container. When the container is tipped, exposing this part of the hardened finish, it looks crystalline in nature.

After nuking this, it's been good for years again.

I learned this on some cork seal that I'd bought and it was set up similarly. I just did it for the heck of it before I threw it away. I was really surprised! Worked great on that, too.

I don't know what the hardened ring at the top is that you're running into? I'm just not sure-you could be right, that could be a cross contamination of some kind...

Putter