While I don't do much refinishing, I do apply lots, and lots of
polyurethane - Here's some of my suggestions:
First, I'm not sure about the 100 grit sanding between coats, or was this an
attempt to remove the previous poly? Either way, start by doing a general
sanding, with about a 180 grit paper in a random orbit sander. This is to
knock down the previous coats and dust nibs. Don't worry about removing all
of the previous coats, you're just looking to smooth out this surface and
make a little tooth on the surface for the subsequent coats to adhere to.
Vacuum or blow off the surface.
I'm not sure if you're using waterbased or oilbased poly - Assuming it's oil
based, thin the poly with mineral spirits - in about a 3 parts poly to 1
part spirits mix. Off the shelf poly is too thick to apply out of the can.
Don't worry if the can says "Do not thin" - That is printed there so the VOC
level stays low enough to sell in California. Next, Use a good brush, I
usually use Purdy brushes, and dip the brush fully in mineral spirits - This
will help the brush flow better.
Dip the brush 1/2 way into the poly mix, and pat it against the inside of
the container - Do not scrape it along the edge - and using a full brush
stroke, with the brush held at a 45 degree angle, glide along and off the
end of the top.
Repeat, overlapping only enough to avoid dry spots.
Charge (Dip the brush into more finish) when you start to feel it drag
Do not fuss with the finish - Let it level itself out while it dries - The
extra mineral sprits in the poly will aid in this.
After the poly dries, scuff (barley the weight of your hand) sand with 320
paper and remove the dust.
Apply about 2 more coats following this procedure, then allow to cure for 2
to 3 weeks, then rub out the finish with mineral oil, pumice, and 0000 steel
Hope this helps
Roycroft Renaissance Artisan
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