How much should I sand after sanding sealer and in between coats for polyurathane?
Answers:
If you want a mirror-smooth surface, sand the wood with successively finer grit papers until you get down to about 220 grit. If you're applying a semi-gloss or nongloss finish, there is no point in doing this much sanding!
TIP: For the smoothest possible finish, before applying sanding sealer, moisten the wood surface with a damp cloth and let it dry completely. This will raise the grain. Sand smooth with 220 grit paper.
Two different products go by the name "sanding sealer." (1) One of them causes wood fibers to stand up and stiffen so they can be sanded off, (2) the other fills the grain to make the surface smooth.
(1) If you're using this kind, sand lightly with 220 grit paper until the surface is very smooth. It will take only a little sanding to do this.
(2) If you are using pore filler, first CHECK TO BE SURE IT IS COMPATIBLE WITH THE BRAND OF POLYURETHANE THAT YOU ARE USING!! Some types of pore filler and polyurethane are incompatible and the polyurethane will not stick permanently. Follow the directions for drying time before sanding and recoating. Sand lightly with 150 grit or finer paper wrapped around a block. The goal is to create a smooth surface. Depending on how rough the surface was to begin with, you may have to sand more or less.
BETWEEN COATS of varnish, sand lightly with 150 grit or finer paper. The goal is simply to roughen the surface so following coats will stick. It is important to follow the label directions on drying times; otherwise you may get a gooey mess that won't dry for weeks or the successive coats may not stick to each other.
Other answers:
The above answer is very good and detailed. It shouldn't have taken 3 months to resolve this question.
The above answer is very good and detailed. It shouldn't have taken 3 months to resolve this question.