Sanding between polyurethane coats


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Old 08-07-02, 05:56 AM
Zathrus
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Sanding between polyurethane coats

Staining some unfinished furniture and the Minwax poly says to "lightly sand" with 220 grit sand paper between poly coats.

Exactly what do they mean by "lightly" sand - just a grazing with a sanding block, or is a random orbital sander w/ a 220 pad safe?
 
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Old 08-07-02, 06:11 AM
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I usually just use a fine synthetic pad (Scotchbrite, etc). Just enough to take a little of the shine off the previous coat.
 
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Old 08-07-02, 06:19 PM
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Sanding between coats of polyurethane (or standard varnish) serves two purposes; removing any minor imperfections in the surface, dust particles, etc., and scuffing the surface enough for the next coat of finish to have something to adhere to.

Unlike lacquer and shellac, which partially dissolve when a new coat is applied, poly (and varnish) are reactive coatings. If you don't sand (just scuff them up a little) the next coat of finish is being paplied ot a slick surface, and won't adhere.

I go the same way tow-guy does - a spot sanding to remove imperfections, then a green Scotch Brite pad to dull the surface sheen.
 
 

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