AW #131.pdf - Karatunov.net

t Use gravity to help fight brush marks. A single spacer
allows positioning your top at a slight angle, to help
the polyurethane flow.
I
itSet up a low-angle light to highlight imperfections.
, Use it's sharp contrast to spot wayward brush strokes,
loose bristles and other debris that appears in the finish.
Wipe the surface with a tack rag after vacuuming. I
never vacuum in my finishing area, though, because
the vac's exhaust stirs up the air.
'Iffi#j
84 American Woodworker ocroBER 2oo7
I Prime your brush
Ii by soaking it in
solvent for a few minutes.The
solvent saturates
the porous natural
bristles, so they
don't soak up the
polyurethane and
become tacky.
Suspend the brush so
it's bristles don't rest
on the bottom of the
glass.
I always slope tabletops for finishing (Photo l).
Thking this step helps me think positively about the
job ahead, because
it makes me feel like I'm doing
everything possible to insure a good outcome.
A low-angle light creates shadows that make it
easy to see imperfections in the finish (see Photo 2
and "Removing Debris", page 90). I use this light
immediately, to check for debris missed by the tack
rag (Photo 3).
Pnlvr AND Sln
Natural bristle brushes work best when the bris-
tles are saturated with solvent (Photo 4).
Saturated bristles release the polyurethane effi-
ciently and make the brush easier to clean.
Thoroughly stir rhe polyurethane. Then pour
enough to complete the job into a separate con-
tainer (Photo 5). I always open a new can of
polyurethane for the final coat.
My secret weapon against brush marks is
Penetrol (Photo 6). Penetrol makes brushing eas-
ier, whether it's hot, humid, cold or dry.
(Polyurethane is usually formulated to perform
best at 70-degrees F. and 50-percent relative
humidity-when do you ever finish in those condi-
tions?) Adding mineral spirits also makes
polyurethane easier to brush, but it thins the fin-
ish, so you might have to apply more coats. Adding
Penetrol doesn't thin the finish. I usually start by
adding two capfuls per pint of polyurethane. Like
mineral spirits, Penetrol slows the drying time,
which increases the chances of accumulating dust
in the finish.
Bnusu AND Roll
Before I brush rhe top, I prime the end grain
(Photo 7) . This method prevenrs ugly drip marks
that can result when you brush the top first, because
drips that soak into unfinished end grain create permanent
marks.
Rather than brushing the top's entire surface, I
divide it into sections that are easier to manage. For
each section, brushing on the polyurethane is a twostep
process.
First I flow it on (Photo 8). Then I brush it out
(Photo 9).
I load the brush by dipping it 7/Z of the way into
the poy'urethane. Then, starting on the top's low
side, I go directly to the surface, wirhout tapping the
brush on the sides of the measuring cup. Just dip
and go, man. I apply the poly'urethane liberally and
reload my brush often. While coating this first secrion
of the top, I also include it's adjacent long edge.