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Q. - Why is it necessary to sand wood before staining or
finishing it?
A. ? Wood is a relatively soft,
porous material, which is why we are able to change its color by applying a
penetrating stain or a dye to it. But since it is soft, it can be scratched and
dented between the time it leaves the sawmill and reaches our garage or
basement workshop. These dents and scratches actually absorb more stain than
does unblemished wood, so unless we sand them out, these dents and scratches
will appear even worse after staining.
In
addition, the final milling process often crushes the top layer of pores in the
board, making it more difficult for our stain to penetrate the wood. A light
sanding will open the pores so that we can achieve the color we want.
Q. - What grit of sandpaper should I use?
A. ? The grit number appears on the
back of each sheet of sandpaper, along with several indecipherable letters and
symbols. Grits below #100 are considered Coarse and are used when you need to
quickly remove a good deal of wood or thick finish, such as when you are
refinishing a floor or a painted door. Grits between #100 and #200 are
considered Medium and are used most often to remove shallow scratches and to
open the pores of the raw wood. Grits between #200 and #400 are considered Fine
and are used between coats of dried new finish. Grits above #400 are Very Fine
and are used for final buffing of the last coat of finish (more on that in
Finishes).
Q. - Why do instructions always call for us to sand ?with the
grain of the wood??
A. ? If you examine any board you
will see that the pores of the wood align themselves in one direction, called
the ?grain? of the wood. Many of these pores look like tiny scratches. When we
sand the wood, the abrasive in the sandpaper often leaves similar scratches in
the wood. When these sanding scratches align themselves with the pores of the
wood, headed in the same direction as the grain of the wood, we don?t notice
them. But when these sanding scratches go ?against the grain,? they stand out
like a sore thumb!
Q. - A friend says I should never over-sand an antique I am
refinishing. Is she correct?
A. ? Absolutely! While we want our new furniture to be
blemish-free, we expect an antique to show signs of age. We call it ?character.?
Some people refer to the mellowness which old wood and an old finish acquire
after decades of sunlight, dusting and daily use as ?patina,? which is what
distinguishes an antique from a nearly identical, but new reproduction.
Naturally we don?t want dangerous splinters or broken rungs on our antiques,
but we do want those shallow scratches, dents, dings and worn spots to remain.
After stripping, but before staining or finishing, sand very lightly with
#180-grit or finer sandpaper just to remove any remnants of the previous finish
and to open the pores for the stain or finish.
Q. - What is the best way to remove
sanding dust?
A. ? With a soft bristle attachment
on the end of a vacuum. Second best is a tack rag, which is generally
cheesecloth moistened with just enough varnish to make it ?tacky.? Do not use a
tack rag if you are going to apply a water-based stain, for any oil left on the
wood will prevent the water-based stain from penetrating the pores of the wood
(more on water-based products in Staining and Finishing). Instead, use a rag
moistened with water.
The
three worst ways are (1.) a dry rag which only pushes the dust around, (2.) a
dry paint brush which only flips the dust temporarily into the air, and (3.) a
blast of compressed air, which sends the dust swirling around the room before
it settles back onto your fresh stain or sticky finish after you leave.
Q. - In the past when I have
applied a stain, my wood turned blotchy. How can I avoid this next time?
A. ? Stains and dyes both rely on
the open pores in the wood to absorb them. Oftentimes, however, those pores
don?t always present themselves in an organized and unified manner. Most
softwoods, such as pine and fir, have an irregular pore structure, especially
around knots and natural blemishes. Many hardwoods, including cherry and maple,
present a similar problem. In nearly every case the board looks perfectly fine
before the stain has been applied, but afterwards turns blotchy as the
irregular pores absorb the stain unevenly. The most well-known exception, one
which generally looks great when stained any color, is oak, for oak has a more
predictable grain pattern and pore structure. Even so, knots in oak are going
to turn blotchy and even the grain in oak can benefit from the following
technique.
The
best way I have discovered to reduce the blotchiness is to apply a coat of
Minwax Wood Conditioner to the wood after sanding but just prior to staining.
The thin-bodied conditioner prevents the larger pores from absorbing too much
stain but won?t completely seal the smaller pores. It is available in both
oil-based and water-based formulas, so read the instructions carefully as they
vary from each other in the amount of time needed to be absorbed into the wood.
If
you insist on staining your pine doors with Dark Walnut stain, however, no
amount of Wood Conditioner is going to eliminate all blotchiness, so don?t
expect miracles. Stains can vary the natural color of wood somewhat, but can?t
be expected to turn a knot-riddled pine board into premium walnut.
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