OT - rubbing out spar varnish

Re: OT - rubbing out spar varnish

Glenn Madsen near San Francisco

>I've used very little birch, so take this with whatever reservations you want...

But I wiped a quart of spar (McCloskey's Gloss), on a bathroom remodel I did. Thinned 20%-30% with naptha, I didn't need to degloss or rub it out. It was over cherry and soft maple, and the maple had two or three coats of shellac under it, but not the cherry. Looks pretty nice two or three years later.

I wonder of it's the birch causing the challenge?

Maybe

Bill Houghton, Sebastopol, CA

>It's got some nice curl, which also means some rough grain spots. And I'm having to finish outside, due to no garage, which may not help.

Tomorrow, I'll try some wet sanding with a fine sandpaper.

Re: OT - rubbing out spar varnish

Jesper, Denmark

>The traditional spar varnishes are phenolin resins with maybe tung oil. They are quite soft when dry, so rubbing out can be a problem.

They are also quite sensitive to proper application technique - use a high quality natural bristle brush and many coats. First coat thinned 50%, second 25 % third a little and then several coats unthinned. Sand lightly between coats with 100 grit. 24 hours between coats minimum. In marine applications, 7 or more coats are normal, mostly for UV protection.

100 grit between coats ??

Bryan in Broad Ripple, IN

>Are you sure you didn't mean 300 or 400 grit between coats. IMO, 100 grit would be waaaay to course for a finishing regimen...even if you sanded as lightly as possible.

-Bryan

My conclusion

Bill Houghton, Sebastopol, CA

>Don't use spar varnish if you expect to need to rub it out, particularly if you're on a deadline. It's possible that it might rub out better if I waited until it had cured more - say, a month. But I didn't have that luxury. Wet sanding with 220 paper followed by No. 0 steel wool, both lubricated with mineral spirits, helped; a coat of wax helped more. It's still not the kind of finish I'll be pointing out to visitors, although, now that the stove's in, there's no sightline that lets you see how bad it is. And the birch, though it finished up darker than the maple countertop (didn't use maple because what I had available had so much tearout it looked like it had been attacked by woodpeckers), is really pretty.