Builders' Forum Archives
Re: Best way to thin varn
Posted by Terry Mcadams on Jul 21, 2004
I use lacquer thinner to thin for a couple of reasons: It not only helps the varnish flow and flatten quickly, but also helps the varnish dry faster and subsequently helps prevent runs and sags in the finish. It also seems to speed curing on humid days. I've used penetrol also, as Charlie says, but I seem to prefer that more for paint than for varnish.
I use the lacquer thinner 5% to as much as 10%. More if it's very hot/humid or if I'm working on vertical surfaces.
As a rule, the thinner the varnish and the varnish coat, the better it will flatten and dry.
Also, give the existing work a good wet sanding with a soft rubber block to give your top coat the best chance at looking good.
Lastly, use small batches, as Charlie says (I can do a deck coat with 2 - 3 oz. of varnish), and work FAST. Very fast. I use a brush (not particurlay clean or expensive, I might add) and quickly lay on the stuff against the grain. Then I scrub the brush round the wet varnish and over to the wet edge of the last section done, even working the stuff into a bit of a lather on vertical surfaces (to stiffen the varnish even more). Then I tip with the same brush with the grain and get the heck away from it. Some folks tip with a separate foam or bristle brush, which is ok, as long as the brush is wet with varnish - a dry brush can cause bumps in the finish.
I use a boat polish as a final step to remove the few dust bumps, and make the finish feel as good as it looks, which I personally think every britework job should do.
The unvarnished truth.
In Response to: Best way to thin varnish? by Melissa on Jul 20, 2004