I started revarnishing my S&G Arctic Tern a week or so ago. I used a quart of System 3 Marine Spar Varnish but went for Satin rather than high gloss varnish this time. Sanded off all of the old varnish and started on the hull. Got four coats on it and it looked great. Then went to the deck, and put several coats on, wet sanding in between. Yesterday when I went out to do what I hoped was going to be the last coat, a cold front had come through, the temp in the garage was probably mid 40s, and I was near the bottom of my quart of spar varnish. As I poured it out I noticed it was thickening quite a bit, but I went ahead and applied a coat anyway. 24 hours later, the deck, which had looked pretty good during the first three coats is now kind of hazy, and in a few spots the varnish turned white--looks like white paint on the deck. How did I screw up, and how do I fix it? There's still a bit of varnish in the bottom of the can, but it appears to be starting to harden--it is now really thick. Can I add some kind of thinner to it and still use it, or am I, as I fear, going to have to make the 70 mile drive to the nearest store that sells marine varnish and plunk down another 40 bucks for a second can? And if I do that, what can I do to keep that surplus varnish from hardening, so that I might use it at the end of the paddling season to touch up the finish? Thanks for any advice you can offer.