Popular Woodworking – August 2019

(Michael S) #1
POPULARWOODWORKING.COM ■ 29

Materials List


WOOD:
4 bdft walnut
MOLD:
4' x 8' sheet of melamine particle board
100% silicone caulk
Paste fi nishing wax
Screws

CONCRETE:
10 lbs. GFRC mix
5 lbs. alkali resistant (AR) glass fi bers
AR glass mesh sheet
Concrete sealer
11 / 2 " Tapcon concrete screws
SPECIALTY TOOLS:
GFRC concrete gun and hopper
Buckets for mixing and measuring
Concrete paddle mixer
Fondant ball tool (cake decorating tool)

Concrete & Walnut Table


Demold, Sand and Seal
Taking a concrete project out of
the form is like Christmas morning
for makers—waiting to see what
your project will look like can be
diffi cult! In many cases, GFRC can
be removed from the form after 24
hours. However, I waited 48 hours
because of the lower temperature
in my shop.
Before demolding, I took the
opportunity to grind down the un-
derside of the table while it was in
the form. Grinding the underside
while still in the form allows you to
use the sides of the form as a guide
to grind to a consistent thickness.
There’s really just one rule to
demolding a concrete piece: don’t
touch the concrete with any tool.
I typically use a cheap “sacrifi cial”
chisel, a mallet and my hands, to pry
the sides of the form away.
After demolding, I wet-sanded
the tabletop by hand with #400-grit
sandpaper. A quick, high-grit wet
sand is an incredibly easy way to


(^3) / 4 "
30° 15"
EXPLODED VIEW
60°
120°
fi nish GFRC. You simply wet sand
until you feel the micro-texture
of the melamine disappear under
your hand (usually only takes a
few seconds in one location). After
sanding, I apply a couple coats of
concrete sealer with a clean micro-
fi ber cloth.
One note before we move on to
the woodworking—depending on
whether there are any fl aws you
want to fi x, you may want to do a
slurry coat (or two) to fi ll in voids
and get a perfectly smooth surface.
A slurry coat is just the same GFRC
mix as used for the face coat, wiped
in by hand to fi ll any voids or pin-
holes in the surface. In my case, I
applied one slurry coat to patch up
some places on the vertical surfaces
where the slumping resulted in
rough patches.
Making the Walnut Base
To support the other end of the ta-
ble, I decided on a rhombus-shaped
leg made from a single walnut board.
61 / 2 "

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