For satin, this is what I do assuming you are starting with good old finish:
-Sand to 150 with orbital and then 3M flat block
-Wipe down with mineral spirits
-Apply Goldspar thinned 10% for first coat with 333 thinner either with foam roller and then tipped with brush (flat large surfaces) or with a high quality brush (I like Corona Europa brushes).
-Sand with 220 and keep repeating the steps until you get 4-6 coats. Use thinner only if necessary
If you want gloss, it's basically the same procedure but I like to start the first 2-3 coats with Interlux Interprime as it builds very quick and levels out to get me to that really smooth surface for the final 2-3 coats of gloss varnish. I prefer Interlux Schooner 96 personally for gloss.
General varnish tips I have learned from doing it a lot.
-Don't go over wet varnish with the brush after it has been down for a couple minutes or it will drag.
-Don't use foam brushes
, in my experience they don't lay down enough varnish and you sand it all off because the coat is too thin.
-Don't varnish out of the can. Pour enough varnish into a plastic cup through a 190 micron paint
strainer every time and work
out of that.
-Scuff sand between coats. You don't want to sand heavy as you are building the finish that's just makes you insane. Lightly scuff with 220 or red scotchbrite just to get a good bond. The only coat that really matters is the last coat. so don't worry about a couple dust spots. For the final coat, I personally, will wet sand it, wash it and then wipe down with mineral spirits and tack cloth. That get's me the glass smooth finish.
-There's a saying about "laying" down a coat of varnish and it's true. You want the varnish to flow off the end of the brush. You aren't "working" it like latex paint
. I have a shallow angle to the brush and let it do the hard work.
-You don't want the brush to drag, if it is the finish will look terrible. Often it is because the varnish is too thick and you can fix this by adding some thinner. I add just enough so that if flows out like a thin real maple syrup.
-Take surgical care of your brushes. I have 4 qts of mineral spirits and I work it through each can blowing it off with the bristles with an air gun after each. Then I keep cycling the cans down the line as cup 1 will get really bad and discard. You should have no dust nits or anything in your brush. If you fail to take care of your brush, it will make you want to swear off varnish forever.
If you made it this far, you are probably thinking, this dude is nuts, no way am I going to do all those steps. And you'd probably be right and why a lot of people go to Cetol. But I really enjoy it and looking at varnish just makes me happy.
Here's an example of what I did. My companionway
steps were getting janky and the top step had cracked. I bored holes for brass rods and reinforced all the steps so it matched. Stripped all the satin varnish off and sanded well. Put on 4-5 coats of Goldspar and it looked and felt great.
And my helm
seat that I keep in high gloss.