AW Extra 3/20/14 – Wipe-On/Rub-Off Finishing

Wipe-On/Rub-Off Finishing

This two-step process guarantees flawless results.

By Kevin Southwick

No brush marks, drips, runs, bubbles,
hairs, dust or orange peel—
and beautiful results every time. For
most furniture projects, it doesn’t
get easier than using a wipe-on/
rub-off finishing process. This two step
method eliminates all the usual
problems because rubbing off all of
the finish that isn’t absorbed by the
wood leaves no wet film in which the
problems can occur. The clear and
important difference between this
method and all others (including
wiping on and leaving a film build)
is the rubbing off. No attempt is
made to build a film on the surface
of the wood. Rubbing off the source
of all the problems is the big trick.

The wipe-on/rub-off method
avoids time spent cleaning brushes
and it dramatically reduces or eliminates
sanding between coats. There
are some limitations, though. This
method can produce only a satin
to semi-gloss finish and the finish
itself won’t be waterproof (see “One
Drawback,” below).

Finishes suitable or formulated
for wiping on and rubbing off are
widely available. They offer convenience,
but you can also easily
concoct your own wipe-on/rub-off
finish. Thinning out an oil-based
brushing varnish is one way. In fact,
just about any finish can be wiped on
and rubbed off, as long as it doesn’t
dry too fast. Shellac, lacquer and
most waterborne finishes fall into
this category; they get sticky before
you can rub them off.

Choosing the right material(s)
for your wipe-on/rub-off finish can
be confusing. Tung oil and linseed
oil are natural vegetable oils that
have been in use for ages. Paste wax
is another classic wipe-on/rub-off
finish. Then there are products like
gel varnish, “Danish oil” and wiping
varnish, as well as custom blends you
can mix up yourself. So how do you
choose the right formula? Here are
three simple considerations.

• The type of resin (or solids).
The materials that remain and
harden to seal the wood after the
solvents evaporate are important
because they have varying degrees of amber tone, working time and
durability. For example, boiled linseed
oil has more amber color than
pure tung oil, while pure tung oil
has a longer working time. Oil-based
varnishes come in a variety of tones,
will dry much faster and are more
durable in every way than both tung
oil and linseed oil.

• The thickness of the material.
Thicker or more concentrated material
is more effective at sealing the
wood, but may be harder to apply
and remove. For example, brushing
varnish straight from the can is
hard to rub off because it’s thick and
goopy. Rubbing off is much easier if
the varnish is thinned out.

• Working time and drying
time. Faster drying time means less
working time, so it’s important to
choose a material that has enough
working time to allow you to get it
all rubbed off before it gets sticky.
You’ll need a long working time if
you plan to rub in the finish with
wet/dry sandpaper. Products with a
lot of oils have the longest working
time—they require a day or longer
to properly cure. Gel varnish, on
the other hand, dries so fast you can
apply two coats in one day.

One favorite wipe-on/rub-off finish
is a combination of equal parts
boiled linseed oil, 100% pure tung
oil, and polyurethane varnish (Photo
1). This blend balances the color
and drying time of the two oils and
is more durable due to the addition
of the polyurethane. You can thin
the blend to make it easier to smear
around and remove. Use a gloss poly
varnish to slightly increase the sheen.
Master furniture maker Sam Maloof
used this type of finish extensively.
He even developed his own branded
version (available at www.rockler.
com). To make a “Danish oil” type
material, simply thin any oil-based
brushing varnish 50% or more with
mineral spirits or paint thinner.

 

Tips for applying

• When you prep the bare wood
for a wipe-on/rub-off finish, sand
to a higher grit than you would for
a film building finish (220-400 grit vs. 150 grit, Photo 2). The quality
of the sheen of a wipe-on/rub-off
finish is determined by the smoothness
or texture of the wood surface
itself. The 150 grit scratches that
would be filled by the layers of a
film-building finish will leave the
wipe-on/rub-off surface looking
dull and lifeless.

• If you choose a finishing material
that has enough working time
you can create a surface that looks
spectacular and feels super-smooth
by rubbing in the first application
of finish (Photo 3). Use a soft block
and fine wet/dry sandpaper (600-
1000 grit) to create a slurry that
helps to seal the wood. You can feel
the difference immediately by running
your finger across the still-wet
wood. This step needs to be done
only once, unless you miss a spot.
Following this application, two
more wipe-on/rub-off coats are usually
enough to create a nice finish;
more coats will slightly increase the
sheen.

• The best way to determine if
you’ve removed all of the finish that
hasn’t been absorbed by the wood
is to continue rubbing with clean
rags until they remain completely
dry, showing no signs of excess finish
(Photo 4). Good rags for this
process are soft and absorbent;
knit cotton and Scott shop towels
are good choices. Note: The finish-soaked
rags are likely to spontaneously
combust, so dispose of them
immediately and properly.

• Only two problems commonly
occur with wipe-on/rub-off finishes
and they’re both easily avoided.
The first occurs when wet finish
that isn’t absorbed by the wood is
left on the surface to create streaks,
rag marks, and sticky or shiny spots.
The second occurs as slower-drying
oils or excess solvents bleed back
out of the pores of the wood and
leave little rings. If they’re still
wet, these rings can be removed by
rubbing. But if they’re allowed to
harden on the surface, they must
be sanded off.

Click any image to view a larger version.

1. Make your own high-quality wipe-on/rub-off finish by blending
100% pure tung oil, boiled linseed oil and polyurethane varnish.

2. Finish-sand to a finer grit than for a film-building finish. Wipeon/
rub-off finish shows scratches that a built-up finish hides.

3. Rub in the wet finish to create a silky-smooth surface.

4. Keep wiping until your last rag comes up clean.

One Drawback—
It’s Not Waterproof

It’s virtually impossible to achieve a 100% waterproof seal
with a wipe-on/rub-off finish alone. Fortunately, there’s an
easy fix: Just apply a thin coat of waterproof material on
top. That’s all it takes to build a consistent, durable film. In
fact, if you want a waterproof coating
that retains the low sheen and very
“close to the wood” look of an oil
finish, the wipe-on/rub-off method
is an excellent and thorough way to
prep the wood’s surface.

After three rounds of wipe-on/rub-off finish on the
entire piece, brush one coat of thinned-out (25-50%) oilbased
brushing varnish on the top or any other horizontal
surface that a glass or cup might find. Don’t bother to
brush vertical surfaces—there’s really no need to make
them waterproof.

If brushing creates a dust or brushmark
problem, you don’t have to
wait until the next day to deal with it. Simply wash off
the messed-up varnish film with paint thinner or mineral
spirits and try again. Most oil-based products can be
removed this way for at least an hour or more.

This story originally appeared in American Woodworker April/May 2011, issue #153.



April/May 2011, issue #153


Purchase this back issue.