Sanding Between Coats of Conversion Varnish

How to select the most effective grit for prep sanding of CV between coats. July 3, 2008

We currently top coat first with a vinyl sealer and then two coats of post catalyzed conversion varnish. We sand between coats with 280 grit sanding sponge. The 280 sponge seems ok for sanding after the vinyl sealer, but not aggressive enough after the first coat of conversion varnish. Any suggestions? We finish flat stock (plywood), cabinet doors, and molding.

Forum Responses
(Finishing Forum)
From contributor A:
Not aggressive enough in which way? Taking too long to sand? If so, is it because you are having to sand out orange peel or junk out of the finish due to a dirty finishing room?

Any courser grit than 280 could leave sanding scratches showing through, although that also can depend on who's CV you are using and how soon you are re-coating. Also, the fastest way to find answers to this type of question is to do some samples of doing it another way, and see the results for yourself.

From contributor G:
How about using a machine for the flat stock?

From contributor D:
A 280 sanding sponge is a joke. The normal rule of thumb is that a sanding sponge is 3X the grit of its stated P value. Therefore a P150 sponge is the equivalent of P400 sandpaper. P150 sponges are about perfect for sanding between coats.

From contributor R:
The sponges work ok if all you want to do is scuff the surface, but the softness of the foam limits their leveling ability - as in removing imperfections or orange peel. A 280-320 silicon carbide on a rubber block or a sander would better suit this process.

From contributor W:
We have also used the sanding sponges for scuffing but use the 150 grit from Dixon. They have also come out with a velcro backed 5" sanding sponge made to work on a random orbit that will speed up your scuffing.