SEE ALSO
 SEE ALSO
Cabinet scrapers 110-111
Sanders 147-150
Fire prevention 211
Face mask/respirator 214
Clear finishes 288,290,294
Opaque paints 290
Primer 290
Spray booth 292
Shellac sticks
Wax sticks
® Removing patches
of glue
When gluing joints,
always wash away
excess adhesive from the
surface using a cloth
dampened with hot
water. If you let the glue
set, 1t seals the wood
and will show as pale
patches after staining or
polishing. Use a cabinet
scraper to remove any
spots of hardened glue
before finishing.
® Sealing knots
Resinous knots will
“bleed” through paint-
work, leaving dark
stains on the surface.
Before you apply a
primer, pick off any
hardened resin, then
paint the knots with two
coats of shellac-based
sealer.
PREPARING THE SURFACE
Woodmust be smooth, clean and free from blemishes
before you apply a surface finish. Paint may cover
minor imperfections, but a clear finish will exagger-
ate every defect, including fine scratches across the
grain. Preparing the surface is the first essential
stage of finishing wood.
FILLING HOLES AND CRACKS
When selecting wood, you should reject poor-quality materials
exhibiting cracks, holes and dead knots, but occasionally it
is necessary to accept a less-than-perfect sample, especially
when buying wood thatis rare or temporarily in short supply.
Even when you have chosen carefully, cracks can open up at
a later stage and must be dealt with before you apply a finish.
Wood putty
| Cellilose filler
Wood putty
A commercial holefilleris a stiff paste made to fill small holes |
and cracks before applying a clear or opaque finish.
Although fillers are made in a range of colors resembling
various common species of wood, at best you can only
expect a close match and the match will hardly ever be
perfect. However, you can adjust the color of the filler with a
drop of wood stain —but since hole fillers may be water-,
lacquer- or oil-based, make sure you always use a similarly
constituted stain.
Cellulose filler |
If you are planning to apply an opaque paint finish, you can
fill blemishes with ordinary spackle or water putty mixed to a
stiff paste.
Shellac sticks
Sticks of solidified shellac are ideal for repairing a crack or
small knot holes before applying any type of finish. They are
made in dozens of wood-like colors.
Wax sticks
Filling sticks of carnauba wax mixed with resins and color-
ing pigments are used to disguise small worm holes and hair-
line cracks in wood. Itis advisable to use them only for
work that is to be wax-polished, as most finishes will not
dry over a wax-filled hole. Special wax crayons are made for
retouching scratches in polished surfaces.
Using fillers
Press filler into the blemish
with a small flexible blade,
such as an artist’s palette
knife, or even the tip of a
chisel. When the filler has set
hard, sand it flush with the
surface of the wood. If the
color match isn’t satis-
factory, touch in the filler
with minute quantities of
artist’s oil paint, using a fine
paintbrush. Let the paint
dry thoroughly before
applying a surface finish.
Melting a shellac stick
Using the tip of a warm
soldering iron, melt the
shellac, allowing it to drip
onto the blemish. While the
shellac is still soft, dip the tip
of a chisel in water and use it
to press the shellac into the
crack or knot. When the
shellac is cool and hard,
pare it flush with a chisel
then sand it with very fine
sandpaper.
Filling with a wax stick
Sand the surface of the wood
and seal it with shellac
before filling with wax. Use
a warmed knife blade to
soften the wax and to press
itinto cracks or small holes.
As the wax hardens, scrape
it flush with the knife, then
burnish it with the back of a
piece of sandpaper.
RAISING A DENT
If you accidentally dent a
workpiece, lay a damp cloth
over the blemish and apply
the tip of a heated soldering
iron. The heat generates
steam, which causes the
wood fibers to swell locally,
lifting the dented section
flush with the surrounding
surface. Allow the wood to
dry before sanding.
284
SANDING WOOD
| Power sanders relieve a woodworker of the chore of smoothing
large flat areas — but for best-quality work, give the wood at
least one final light sanding by hand.
Abrasive papers
A variety of abrasive materials glued to paper backin g sheets
are used to smooth wood and hardened surface finishes. All
these abrasives are known collectively as sandpaper, though
this term was originally used to describe glasspaper only.
Glasspaper is pale yellow in color. It wears quickly and,
although not really suitable for fine woodwork, is a cheap
option for sanding softwoods. It is also known as flintpaper.
Garnet paper is made from a reddish-brown natural
mineral that forms hard particles with sharp cutting edges.
Garnet paper is a good-quality abrasive both for softwoods
and hardwoods.
Aluminum-oxide paper is even harder than garnet paper.
Itis produced in standard-size sheets for handwork and is
also used widely as an abrasive for power tools. Aluminum-
oxide papers are available in different colors. This type of
abrasive is especially good for sanding dense hardwoods.
Silicon-carbide paper varies from dark gray to black. It is
| made from a synthetic material and is used mainly for finish-
| ing metals or, with water as a lubricant, for smoothing
paintwork between coats. Often referred to as “wet-or-dry
| paper,” it is used without a lubricant for sanding hardwoods.
| A pale-gray silicon-carbide paper dusted with zinc-oxide
| powder that acts as a dry lubricant is preferable for rubbing
| down French polish, which would be spoiled by using water
as a lubricant.
Grading sandpaper
Sandpapers are graded
according to abrasive-
particle size and are roughly
classified as having very
coarse, coarse, medium,
fine or very fine grit. They
are also graded by number
(typically from 600 to 40 or,
using another system, from
9/0 to 1) — the higher the
number, the finer the grit.
Use progressively finer grits,
so that each grade removes
the scratches left by the
previous paper. As a guide,
coarse to fine grades are
suitable for general work
and very fine grades for
cutting back surface finishes.
In addition, there are
closed-coat or open-coat
types of sandpaper. Closed-
coat papers have particles
grouped closely together for
fast sanding, whereas open-
coat abrasives have large
gaps between the particles,
which clog less readily, and
so are better for resinous
softwoods.
Very coarse
Medium
| the arris (the sharp “line”
Sanding by hand
Tear sheets of sandpaper
into convenient strips over
the edge of a bench. Wrap a
strip around a cork sanding
block and use it to smooth
a flat workpiece, always
working with the grain (1).
Take care not to round over
sharp corners inadvertently
when you approach an edge
— but if you want to remove
where two surfaces meet),
sand a chamfer deliberately,
using the same block (2).
Wrap sandpaper around a
shaped block when you are
sanding moldings (3).
Lay aside sanding blocks
and use your fingertips to
apply pressure to sandpaper
when smoothing curved
surfaces or for very light
sanding (4). When sand-
paper becomes clogged with
wood dust, tap it against
the workbench to clear the
abrasive particles.
When the surface appears
to be as smooth as possible,
in order to raise the grain,
dampen the wood with a
wet rag and leave it to dry.
A final light sanding will
then remove the fine fibers,
leaving a perfect finish.
Finally, remove the wood
dust with a cloth dampened
with mineral spirits, or use a
commercial “tack rag” (a
2 Removing an arris
4 Use fingertip pressure
for light sanding
® Storing sandpaper
cloth impregnated with Wrap sheets of sand-
resin). paper in plastic to keep
them dry while being
Sanding end grain stored.
Rub your finger along the
surface of end grain before
sanding. It will feel rougher
in one direction and rela-
tively smooth in another.
Sand in the smoother direc-
tion for a superior finish.
Abrasive papers
1 Glasspaper
2 Garnet paper
3 Aluminum-oxide paper
4 Silicon-carbide paper
S Self-lubricating
silicon-carbide paper
SEE ALSO
Orbital sanders 148-150
Face mask/respirator 214
Goggles 214
Safety tips 284
Abrasive papers 285
EN
a
Fill the grain of
coarse-textured wood
coarse-textured open-grain
woods such as mahogany,
walnut, oak and ash with a
grain filler before applying a
glossy finish. If you omit this
process, a pitted, uneven
finish will result.
The best method is to apply
successive coats of varnish,
rubbing down in between,
until the pores are filled.
Color-matching of filler to
wood is then not needed.
However, this is a laborious
process, so most wood-
workers prefer to use a com-
mercial grain filler sold as a
thin paste colored to match
a variety of woods. Choose
a filler slightly darker than
your wood, since filler dries
to a lighter tone and you can
always adjust its color by
adding a compatible wood
stain to the paste.
Rub the filler onto the
wood with circular strokes,
using a coarse cloth to re-
move any excess filler, and
let it harden overnight be-
fore sanding very lightly
with a fine-grade paper in
the direction of the grain.
AI EE
BLEACHING AND STAINING
In most cases, a woodworker will apply a clear finish
> E не!
== клип
directly to a sanded workpiece, but occasionally it
may be necessary to bleach discolored wood before
polishing or varnishing. Conversely, you might want
to enhance the color of an unusually dull piece of
wood with a light coat of stain or use stain to blend
poorly matched samples of the same species of wood.
Filling stained wood
If you fill the wood after
staining, the dried filler can
only be sanded very lightly
or you will change its color
— and if you stain after fill-
ing, uneven absorption may
result in patchiness. The
safest way is to seal the
stained wood with a coat of
the intended clear finish,
then once it is dry, fill the
grain. This way, the sealer
coat will protect the color
when you sand the filler.
Using sanding sealer
In place of grain filler, use
a commercial sanding sealer
when preparing fine-tex-
tured woods or man-made
boards for finishing. Brush
the sealer on and sand it
when dry with a fine-grade
paper. Seal again and rub
down the dried surface with
0000 grade (extra-fine)
steel wool. Some varnishes
may not adhere satis-
factorily when applied over
sanding sealer.
BLEACHING WOOD
Two-part commercial wood bleaches remove the color from
wood by chemical action. Having applied the bleach itself,
it is necessary to use a neutralizer to arrest the process. Not
all woods bleach successfully. Chestnut or rosewood, for
example, do not respond favorably to bleach, whereas oak
or birch react well. Always test a sample of the wood before
attempting to bleach your workpiece. Wood bleach is a potent
chemical — so follow the manufacturer's recommendations
with care. Wear protective gloves, goggles, old clothes and an
apron whenever you handle the chemicals.
Apply an even coat of bleach to the wood, using a clean
white rag or an old bristle or nylon brush. Keep checking
on the reaction for up to 20 minutes and, as soon as the
required tone is achieved, wash the surface with the
neutralizer. After about four hours, wash the wood again
with clean water, leave it to dry and then sand it smooth.
Wood stains
1 Colored water-based
stain on maple
2 Walnut water-based
stain on beech
3 Light-oak alcohol-
based stain on beech
4 Red-mahogany oil- ,
based stain on beech ©
Bleached utile 020008
WOOD STAINS
Wood must be perfectly
clean, grease-free and sanded
smooth in the direction of the
grain before you apply wood
stain. After using a powered
orbital sander, sand by hand
to remove the swirls of fine
cross-grain scratches left on
the wood. Unless you wet the
wood first and sand it smooth,
a water-based stain will raise
the grain, leaving a rough
surface after it dries.
TYPES OF STAIN
Ready-mixed wood stains
are available in an enormous
range of colors from most
paint or hardware stores, but
dry, powdered pigments that
you have to mix for yourself
usually have to be bought
from a specialist supplier.
Ready-mixed stains are very
convenient, but many pro-
fessionals recognize the
advantages of being able to
mix the exact colors they
want using dry pigments.
Water-based stain
Water-based stains flow and
penetrate well and, because
they are relatively slow to
dry, it is easy to get an even
distribution of color. You
can even shade water stains
when they are on the wood,
using a damp rag to remove
color. Once it is dry, any
wood finish may be applied
over a water stain. You can
buy ready-mixed stain or
dry, water-soluble aniline
powder. To make your
stain, mix about loz (30g)
of the powder in 1 quart
(1 litre) of warm water.
Let the stain cool before
applying it.
Alcohol-based stain
Alcohol-based stains are not
popular with amateur wood-
workers because, being
dissolved in methylated
alcohol, they dry very fast
and skillful application is
required to avoid overlaps
and hard edges showing
when the stain dries. For this
reason, alcohol-based stains
are often sprayed on. This
type of stain will not raise
the grain of the wood. Buy
it ready-mixed or in powder
form to be mixed with
alcohol, using the same pro-
portions recommended for a
water stain. Adding a little
shellac (French polish)
makes it easier to brush on
alcohol stain and helps bind
the pigment.
An alcohol-based stain
may “bleed” through a sub-
sequent coat of French
polish or brushed-on cellu-
lose lacquer, but a sprayed
lacquer finish will not be
affected in the same way.
Oil-based stain
Oil-based stains evaporate
reasonably quickly, but
there is usually plenty of
time to achieve a satisfactory
result. These stains, based
on mineral spirits and oil-
based solvent naptha, will
not raise the grain. Oil-based
stains will be redissolved by
the solvent content of poly-
urethane varnish and wax
polish. Seal the stained sur-
face with one coat of shellac
sanding sealer before apply-
ing varnish and two coats
before applying wax. Oil
stains are only available
ready-mixed.
APPLYING
WOOD STAIN
You can apply stain to a
flat area of wood with a
good-quality paintbrush or
a paint pad. Spread the stain
liberally and evenly; work
with the grain and blend
wet edges as quickly as
possible. As soon as you
have applied a coat of water
stain, wipe the wet surface
with a soft, dry cloth to dis-
tribute the color evenly and
absorb excess stain.
You may prefer to apply
stain with a ball of clean rag
— especially if you have to
color a vertical panel,
since it is easier to control
runs. Using a rag is also the
only really practical way to
stain turned components.
Wearing protective gloves,
saturate the rag in stain,
then squeeze it out to avoid
dripping spots of color on
the wood. Drips and runs
may show through the
finished coat of stain unless
you can blend them before
they begin to dry.
MAKING A TEST STRIP
Each species of wood
absorbs stain differently,
affecting the color of the
Stain as it dries. The type of
finish you use to overlay the
stain also has an effect on its
color and tone.
Before you stain a work-
piece, make a test strip,
using a scrap of the same
wood. Paint the test strip
with one coat of stain and
allow it to dry; then paint
the strip with a second coat,
but leave a small section of
the first application exposed
for comparison. Two coats
of stain are normally suffi-
cient, but for the purposes
of the test make three or even
four applications and leave
them to dry thoroughly.
Paint a band of clear finish
along one half of the test
strip to see how it affects
each coat of stain.
UNSTAINED BEECH
CLEAR FINISH
FIRST APPLICATION
OF STAIN
SECOND APPLICATION
THIRD APPLICATION
Test strip
FUMING WOOD
Exposure to ammonia fumes
chemically colors woods
that contain tannic acid.
Oak — the most popular
wood for fuming — turns a
golden honey color to a
medium-dark brown,
depending on the length of
exposure. Mahogany,
chestnut and walnut can also
be colored with ammonia.
You can obtain a strong
ammonia solution (27 to 30
percent) from a retail
pharmacy or chemical-
supply house. Alternatively,
you can use ordinary
household ammonia, though
expect the process to be
slower. Ammonia irritates
the eyes, nose and throat —
so build a fume cupboard
either outside or in a well-
ventilated room and wear
goggles plus a face mask or
respirator when handling
the chemical.
Making a fume cupboard
To construct a makeshift
fume cupboard, make a
scrap-wood framework to
enclose the workpiece, then
drape the frame with black
plastic sheeting to create an
airtight tent. Seal all seams
and joints with duct tape.
Don’t use transparent
287
plastic, as daylight can affect
the color change.
Place several saucers con-
taining ammonia solution
inside the tent along with
the workpiece. Do not
include metal hardware or
exposed screws, since they
will stain the wood.
Leave the tent sealed for
about 24 hours to obtain a
medium-dark color. Check
from time to time if you want
a lighter tone. Even when
you remove the workpiece,
the reaction will continue
for a while and the wood
will darken still further.
PLASTIC COVER
FRAMEWORK
Home-made fume cupboard
FRENCH POLISH
French polish, the most celebrated wood finish of
Victorian times, is still very popular today. The
polish is made by dissolving shellac, a secretion of the
lac insect, in industrial alcohol. It can be burnished
to an almost glass-like texture that belies its vulner-
ability to scratching and its susceptibility to alcohol
and water, which etch the surface leaving white
SEE ALSO
Safety tips 284
Abrasive papers 285
Wood stains 286-287
i Waxes 294
stains. Despite these obvious disadvantages, French
polish is such an attractive finish that many wood-
workers are prepared to put in hours of practice in
order to master the technique.
French polishes
1 Unfinished mahogany
2 Mahogany finished
with button shellac
3 Mahogany finished
with garnet shellac
4 White shellac on
maple
TYPES OF SHELLAC
“Orange” and “white” liquid
shellacs are widely available
commercially, or you can
make your own blends by
dissolving dry shellac flakes
in methylated alcohol. Once
mixed, liquid shellac has a
limited shelf life, after which
it will not dry hard.
Blond shellac
This is the highest grade of
shellac flakes, ranging from
super-blond, the lightest in
color, to various grades
known as “lemon.”
Button and garnet shellac
Button-lac was once shellac
sold in the form of discs or
“buttons,” but these have
not been available for years.
Now the term is used to
describe a less-refined grade
of shellac flake that is darker
in color than the blond and
lemon varieties. Garnet is a
rich red-brown in color.
Orange shellac
Commercial liquid shellac
suited to most wood finish-
ing purposes, with a longer
shelf life than commercial
“white” shellac. It is usually
sold in 31b cut, or three
pounds of dry shellac mixed
with one gallon of alcohol
by the manufacturer. This
is a good rough guideline for
mixing dry shellacs as well.
White shellac
Bleached “white” shellac
has a short shelf life in dry
form, andis therefore always
sold premixed. Its liquid
shelf life is short. It is suit-
able for use on marquetry or
other low-wear applications,
especially over light-colored
woods.
Dewaxed shellac
Natural shellac contains
waxes that very slightly dull
the appearance of the film,
but also make it more
flexible. To achieve finishes
of the highest gloss and
hardness, manufacturers
remove the wax.
Colored shellacs
Shellacs can be tinted with
alcohol-soluble dyes. A
green color can be used to
“tone down” raw-red
mahogany; a red-brown
will enrich dull-brown wood.
288
BRUSHING SHELLAC
Traditional French polish-
ing demands skill and
practice before you can
achieve perfect results.
Consequently, many wood-
workers prefer to brush
slightly thinned shellac onto
the wood then rub down
between coats rather than
apply the polish in the tradi-
tional manner.
The technique for brushing
shellac is easy to master. Use
a soft brush to apply an even
coat, then after 15 to 20
minutes, rub down lightly
with self-lubricating silicon-
carbide paper and apply a
second coat. Having applied
a third coat in the same way,
rub it down with 0000 steel
wool dipped in wax polish,
then after five minutes,
burnish with a soft cloth.
Applying brushing French polish
Use a soft brush to apply an even
coat of shellac to the surface.
Rubbing down with steel wool
Rub the final coat lightly in the
direction of the grain.
TRADITIONAL
FRENCH POLISHING
Traditionally, French polish
is applied, thin layer upon
layer, using a ball of cotton
wrapped in a white linen rag
to make a soft pad known as a
“rubber.”
Making a rubber
Upholsterer’s skin wadding
is the best material for mak-
ing a rubber, but ordinary
cotton will do almost as
well. Take a handful of the
material, squeeze it roughly
egg-shaped and place it in the
center of a 9 to 12in (225 to
300mm) square of linen (1).
Fold the fabric over the
cotton (2), then turn in the
edges (3), gathering the loose
material in the palm of your
hand (4). Smooth out any
wrinkles across the sole of the
pad.
а
1 Place ball of wadding on a
square of linen
a
= } i Je y
С ==
4 Hold in the palm of your hand
Charging a rubber
Unfold the linen square, then, holding the rubber in the
palm of your hand, pour shellac polish onto the pad until it is
fully charged but not absolutely saturated. Fold the rubber
again, as described left, and press it against a scrap board to
squeeze out the polish and distribute it evenly across the sole.
Use your fingertip to apply a drop of linseed oil to the sole to
act as a lubricant.
Applying the polish
To apply French polish to a flat surface, first make over-
lapping circular strokes with the rubber, gradually covering
the whole panel with shellac (1). Then go over the surface
again, this time using figure-eight strokes (2). Varying
the stroke ensures an even coverage. Finish with straight
overlapping strokes parallel to the grain (3).
Very little pressure is required with a freshly charged
rubber, but gradually increase the pressure as the work
proceeds. Always keep the rubber on the move, sweeping it
on and off the surface at the beginning and end of each com-
plete coverage. If you stop with the rubber in contact with
the work, it will stick and scar the polish, in which case you
must let it harden thoroughly before rubbing it down with
very fine self-lubricating silicon-carbide paper. Recharge
your rubber with polish as necessary and add another spot
of linseed oil when the rubber starts to drag.
Assuming the first application is free from blemishes, leave
it to dry for about half an hour, then repeat the process.
Build up four or five coats in this way, then leave the shellac
to harden overnight. Keep your rubber in a screw-top glass
Jar while you allow the polish to dry.
The next day, sand out any runs, dust particles or rubber
marks with silicon-carbide paper before applying another
four to five coats of polish. Judge for yourself when you have
built up a protective body of polish with the required depth
of color, but 10 to 20 coats will be sufficient.
Polishing moldings and carvings
Panels with large shallow moldings can be polished with a
rubber, but use a soft brush to apply slightly thinned shellac
to deep moldings or carvings. A squirrel-hair brush from a
specialist supplier is ideal, but you can make do with an
ordinary good-quality paintbrush. Apply the polish rela-
tively quickly and evenly, but not too quickly or it will run.
When the shellac has hardened, spirit off with a rubber as
described below, but only burnish lightly or you will remove
too much polish from the high points.
Spiriting-off
The linseed-oil lubricant leaves streaks in the surface of the
polish. Remove the streaks and burnish the polish to a gloss
finish using a rubber practically empty of shellac but with a
few drops of methylated alcohol on the sole. Apply the
rubber to the polished surface using straight parallel strokes
only, gliding on and off the panel at the beginning and end of
each stroke. Recharge with more methylated alcohol as soon
as the rubber begins to drag. Leave the work for a couple of
minutes to see if the streaking disappears. If it doesn’t, spirit
off again until you have achieved the required finish. After
half an hour, burnish the surface with a dry, soft rag, then
leave the work for at least a week to harden completely.
Creating a satin finish
If you don’t care for a high-gloss finish, matte the fully
hardened surface by rubbing it lightly with a ball of 0000
steel wool dipped in soft wax polish. Use straight, parallel,
overlapping strokes until the surface is dulled evenly, then
burnish it to an attractive satin sheen with a soft cloth,
adding a little more wax polish if necessary.
289
1 Cover the panel with
circular strokes
2 Continue with figure-
eight strokes
3 Finish with straight,
parallel strokes
SEE ALSO
Safety tips 284
Abrasive papers 285
Applying French polish 289
Spraying finishes 292-293
Waxes 294
Arris 311
Lacquers, varnishes
and paint
1 Cellulose lacquer
on maple
2 Clear catalyzed
lacquer on pine
3 Black catalyzed
lacquer
4 Clear polyurethane
varnish on utile
5 Tinted polyurethane
‘varnish on oak
6 Solvent-based paint
on pine
UNFINISHED WOOD
LACQUER, VARNISH AND PAINT
appropriate solvents, time between coats and pre-
Lacquer, varnish and paint are grouped together here
because these finishes are applied in similar ways,
cautions for use. Most paints are in effect clear
either by brush or spray gun. Consult the label for
lacquers or varnishes with additional pigments.
Nitrocellulose lacquer
This has been a popular
industrial wood finish for
decades, primarily because
it dries extremely quickly.
There are special brushing
varieties, but lacquer nor-
mally has to be sprayed on
to achieve the desired result.
Lacquer dries by solvent
evaporation, leaving a
surface layer that is partly
redissolved by the next
application — a process that
eventually results in one
integral coat of lacquer.
Nitrocellulose lacquer is
practically water-clear and
will hardly change the color
of the wood to which it
is applied. It forms a hard
finish that is resistant to
heat and moisture.
PRIMER
UNDERCOAT
Catalyzed lacquers
A catalyzed lacquer cures by
chemical action — the lacquer
won't set without the intro-
duction of a hardener. With
precatalyzed lacquers, the
catalyst and lacquer are
mixed by the manufacturer,
although setting does not
occur until the finish 1s
exposed to air. An acid-
catalyzed lacquer is supplied
as two separate components
for the woodworker to mix
just before applying it to the
work. Catalyzed lacquers
are very transparent — they
are also exceptionally hard-
wearing and stain-resistant.
Both gloss and matte
lacquers are available, and
you can buy opaque black
and white acid-catalyzed
lacquers as well as the more
familiar clear variety. All
catalyzed lacquers can be
diluted with special thinners
for spraying and some are
formulated for brushing on.
Most are extremely toxic.
TOP COAT
Varnishes
Synthetic resins such as
polyurethane are used to
make modern wood var-
nishes that are heat-resistant,
waterproof and extremely
hard-wearing. Although
most varnishes can be used
straight from the can, some
are supplied with a catalyst
that is added just before the
varnish is applied. These
two-part varnishes are so
resistant to abrasion that
they are used for finishing
wooden floors, but they
have a relatively short pot
life and adhesion between
coats is not always satis-
factory. They also give off
unpleasant fumes.
Exterior-grade varnishes
are made to be weather-
resistant — and “yacht
varnish,” which will with-
stand exposure to salt water,
is especially suitable for
coastal climates.
There are clear varnishes
that dry to a matte, satin or
gloss finish, and tinted var-
nishes are available for
coloring wood. As a tinted
varnish does not penetrate
the wood like a true stain,
there is always the possibility
of color loss due to localized
wear. As a safeguard, apply
one or two additional coats
of clear varnish to preserve
the color. Tinted varnish 1s
useful for adjusting the
color of a workpiece that has
already been varnished. You
can apply varnish with a
paintbrush or dilute it with
thinner for spraying.
Paint
Solvent-based paints for
wood are made from solid
pigments suspended in a
synthetic resin, such as
alkyd, vinyl, acrylic, urea
or polyurethane, mixed with
oil. Certain additives alter
the quality of the paint to
make it glossy, matte, satin,
fast-drying and so on. Most
solvent-based paints have a
liquid consistency, but you
can also buy thixotropic
(nondrip) paints that are
jelly-like in the can and flow
only when agitated by brush-
ing them onto a surface.
Paints with specific proper-
ties are used in sequence to
build up a hard-wearing
protective coating. A primer
is used first, to seal the bare
wood and prevent absorp-
tion of subsequent coats. It
is followed by one or two
applications of a heavily
pigmented undercoat to
obliterate the primer and
build up a body of paint.
The final top coat provides a
wipe-clean surface of the
required color and texture.
Opaque paints are intended
for finishing cheap hardwood
as well as softwood and
man-made boards. Resin-
based paints can be applied
by brush, and all but thixo-
tropic paints can be sprayed.
Water-based paints will raise
the grain if used to finish
wood.
When you have finished work, brush out excess paint, var-
nish or lacquer on newspaper in order to clean the bristles.
Flex the brush in the finish-maker’s recommended thinner
(mineral spirits for most paints and varnishes), then wash
the dirty thinner from the bristles with hot soapy water and
rinse them. Shape the bristles with your fingers while they
are still wet. When dry, wrap the bristles in soft paper and
slip an elastic band around the ferrule of the brush to
secure the wrapping.
290
APPLYING FINISHES BY BRUSH
Spraying produces the most professional-looking finish, but it
is expensive to build and equip a spray booth that complies with
health and safety recommendations. Consequently, applying
clear finishes and paints with a brush is the only viable option
for many amateur woodworkers. However, provided you use
well-maintained, good-quality brushes and exercise care and
patience, you can achieve more than satisfactory results
employing ordinary workshop facilities. Buy a range of
brushes — say +, I and 2in (12, 25 and 50mm) wide — for
general work, and a 4in (100mm) brush for coating large
flat surfaces.
Brushing cellulose lacquer
It requires a certain amount of experience to apply a brushing
lacquer without leaving brush marks or ridges that are diffi-
cult to rub down. First, using a soft cloth or a brush, apply
lacquer thinned by 50 percent to act as a sealer coat. Load
a soft brush with full-strength lacquer and, holding the
bristles at a shallow angle to the horizontal surface, lay
the finish onto the surface with long, straight strokes. Don’t
attempt to brush it out like varnish, and avoid going back
over the same area twice. Quickly pick up wet edges with
fresh lacquer and allow the brush marks to flow out by
themselves. Build up two or three coats of lacquer, rubbing
down with very fine silicon-carbide paper in between. Each
coat usually takes about an hour to dry — but check the
manufacturer’s instructions. If you are unhappy with the
appearance of the final coat, flatten it with sandpaper again
and apply a commercial rubbing compound with a soft cloth
to buff the finish.
Some experienced woodworkers prefer to use a “pull-over
solution” made from one part cellulose thinner mixed with
three parts mineral spirits to put the final shine on nitro-
cellulose lacquer. This is not an easy technique to perfect and
you must take care to avoid stripping the surface by applying
too much solution. Having flattened the lacquer with silicon-
carbide paper, moisten a cloth pad with pull-over solution
and apply it to the surface, using overlapping circular
strokes followed by straight ones in the direction of the
grain, as when applying French polish.
Applying acid-catalyzed lacquer
Chemical composition and balance is crucial to the curing
of acid-catalyzed lacquer, so it is essential to follow the
manufacturer’s recommendations for mixing the com-
ponents and preparing the surface of the wood. Clean the
wood well, since the presence of grease or wax, for example,
can delay curing for days.
Mix just enough lacquer for your needs, and don’t return
the residue to the original container or the entire contents
will become unusable.
The specific method of application may differ from product
to product, but as a rule you can brush a liberal coat of
lacquer onto the wood, spreading it with straight, parallel
strokes along the grain. There is no need to brush it out like
varnish — just leave the film to settle naturally. When you are
coating a large area, work relatively quickly to blend wet
edges before the lacquer starts to set. This will probably take
between 10 and 15 minutes. Apply a second coat about two
hours later and, having rubbed it down lightly with very fine
silicon-carbide paper to remove dust particles, add a third
coat two hours after that. For perfect adhesion between
coats, try to apply all three in the same day.
If you want a mirror finish, leave gloss lacquer to harden
for 24 hours, then buff it with a polishing compound on a soft
cloth. For a satin finish, rub the gloss lacquer with 0000
steel wool dipped in wax polish then buff with a clean, soft
rag.
Applying varnish
When finishing bare wood
with clear or tinted varnish,
first apply a sealer coat
thinned by 10 to 20 percent
with mineral spirits. Use a
soft cloth pad to rub it into
the wood in the direction of
the grain, or brush on the
sealer coat where a pad
would be inconvenient.
Apply the second coat by
brush not less than six hours
later — and if more than 24
hours have elapsed between
coats, key the surface of
gloss varnish with a very fine
silicon-carbide paper.
Remove the wood dust,
using a cloth dampened with
mineral spirits, before
brushing on the varnish. For
a hard-wearing surface,
apply a third coat in the
same way.
To load a brush with var-
nish, dip only the first third
of the bristles into the finish
and touch it off on the inside
of the container to remove
excess liquid. Do not drag
the bristles across the rim of
the can, as that promotes
bubbles in the varnish —
which, if transferred to the
work, may end up set in the
surface coating.
Paint the varnish onto the
wood, brushing it in differ-
ent directions to spread the
finish evenly and blend each
new coat with the wet edges
of the previous application.
Finally, “lay off” with light
strokes in the direction of
the grain. Don’t brush back
over a coat of varnish once
it has begun to set or you
will leave permanent brush
marks. If this should
happen, leave the finish to
harden overnight then rub
out the brush marks and any
other blemishes with silicon-
carbide paper lubricated
with water.
If dust particles settle on
your final gloss surface,
either rub down and varnish
again or modify the finish
with steel wool and wax.
Dip 0000 steel wool in wax
polish and burnish the
surface in the direction of
the grain. Buff the treated
surface with a rag to raise an
attractive soft sheen free
from obvious imperfections.
291
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Apply a sealer coat of varnish with a cloth pad
Applying paint
Most solvent-based paints
are applied like varnish,
brushing them out to provide
an even cover, then laying
off with parallel strokes of
the brush. However, there
1s no need to brush out
thixotropic paints — instead,
apply a fairly liberal coat of
paint, brushing with virtu-
ally parallél strokes only,
and leave the brush marks to
flow out naturally.
Allow enough time for each
coat of paint to dry accord-
ing to the manufacturer’s
instructions, then rub down
with a very fine silicon-
carbide paper and wipe the
surface clean with a rag.
Leave the final top coat to
dry overnight in a dust-free
environment before hand-
ling the workpiece again.
AVOIDING RUNS IN
PAINT OR VARNISH
If you neglect to brush out
a liberal coat of normal
solvent-based paint or var-
nish on a vertical surface, it
will sag to form a heavy ridge
similar in appearance to a
draped curtain. Prevent
“curtaining” by applying an
even coat, then lay off with
upward brush strokes (1).
Teardrop runs are caused
by flexing a loaded brush
against a molding or the
corner of a panel. Always
apply paint along moldings
— never across them — and
pay particular attention to
brushing out in both direc-
tions from corners where
two moldings meet (2).
When painting up to the
edge of a panel, brush out-
ward away from the center
(3). If you brush back
against the arris, you will
scrape paint off the bristles,
leaving it to run down.
fra]
| | АНИ il
1 Laying off
3 Brush toward edge
SPRAYING WOOD FINISHES
Once you have mastered the basic techniques, you
can finish a workpiece with a perfectly even coat of
varnish, paint or lacquer, using a spray gun and com-
pressor. When these volatile finishes are distributed
as a fine mist in the air, they form a potentially
explosive environment and constitute a serious health
hazard. You should therefore either spray woodwork
outside or build a spray booth equipped with an |
efficient exhaust system. However, check with your
local authorities to see if you are allowed to spray in
your locality and to make sure that you will not be
violating any fire or safety regulations.
SPRAYING EQUIPMENT
SEE ALSO
Goggles 214
Respirator 214
Safety tips 284
Abrasive papers 285
Lacquer, varnish
and paint 290
Waxes 294
HORN AIR CAP
FLUID TIP
Spray gun
Paint-spraying equipment mixes pressurized air with a liquid
finish and deposits it in the form of very fine particles on the
surface of the work.
Spray gun and compressor
An electrically powered
compressor pressurizes fil-
tered air and delivers it via a
flexible hose to a spray gun.
Squeezing the gun’s trigger
opens an air-inlet valve,
allowing air to flow through
the gun and exit through the
fluid tip —a small hole in the
center of the air cap — where
it is mixed with paint or a
clear finish siphoned from a
sealed container that is usu-
ally mounted below the gun.
Some of the pressurized air
is diverted to horns on either
side of the fluid tip, where it
emerges through tiny holes,
causing the spray to spread
out like a fan. Air flow and
fluid output are modified by
turning valve screws on the
back of the spray gun. Some
guns are made with an addi-
tional air-adjustment valve
à at the base of the handgrip
@, for finer tuning.
AIR-FLOW SCREW
FLUID-OUTPUT
SCREW
HANDGRIP
AIR-ADJUSTMENT
VALVE
AIR-SUPPLY HOSE
FINISH CONTAINER
Cleaning a spray gun
When you have finished
spraying, empty the finish
container and add clean
thinner. Operate the gun
until perfectly clear thinner
emerges, then release the air
pressure, dismantle the air
cap and clean the compon-
ents with a rag dampened
in solvent. Use a wooden
toothpick to clear a paint
blockage in the cap.
Use a toothpick to
clear a blockage
Building a spray booth
The only safe way to spray
indoorsis to construct a fully
enclosed booth that will
isolate this activity from the
rest of the workshop. Install
a powerful exhaust fan on
an outside wall to remove
noxious solvent fumes.
However, these fumes create
such a flammable atmosphere
that even a sparking electric
motor can cause them to
ignite — so obtain a fan with
an explosion-proof motor
from a specialist supplier and
fit a paint filter in front of the
fan to collect the overspray.
Y ou will also need explosion-
proof lamps that can be
switched on or off from
outside. Check with your
supplier that your com-
pressor is safe to use inside
the booth, or install it out-
side with a connection for the
hose fitted to the booth wall.
Ideally, include a water trap
at this point to prevent
moisture in the pressurized
air from condensing in the
hose and spoiling the work.
To hold small workpieces,
make a turntable, using a
disc of chipboard screwed to
an old swivel-chair base, and
stand it in front of the filtered
fan. Support larger pieces on
sawhorses.
292
THINNING PAINT,
VARNISH OR LACQUER
All finishes, most of which
are sold in a brushable con-
sistency, must be diluted
with the appropriate thinner
to render them fluid enough
to be sprayed. Check manu-
facturers’ recommendations
for the type of thinner to use
and the ideal ratio of thinner
to finish.
Having measured out and
mixed the components, use
the following rough rule of
thumb to test the consistency
of the finish. Stir the finish
with a wooden stick, then
lift it out and watch how the
finish runs from the tip.
When the finish runs in a
steady, continuous stream,
it is about right for spraying.
A slow, interrupted stream
indicates an over-thick
consistency that will not
spray efficiently. It is not so
easy with this method to tell
when a finish is too fluid, but
a short burst of diluted finish
sprayed onto a vertical
practice board will give you
a clue — if it runs almost at
once, it is too thin.
For a more accurate gauge
of consistency, obtain a
viscosity cup from the spray-
equipment manufacturer.
Fill the cup, which is similar
to a funnel, with thinned
finish and time how long it
takes to empty. Adjust the
consistency until the time
corresponds with the
recommended figure.
Use a viscosity cup to test the
consistency of a finish
BASIC SPRAYING TECHNIQUES
If you have never sprayed finishes before, it is best to practice
on a piece of scrap board before spraying a workpiece.
Spraying a vertical panel
To spray a vertical panel, hold the gun approximately
8in (200mm) away from the surface, with the air horns
turned horizontally to create a vertical fan-shaped spray
pattern. Point the gun directly at the work and keep it mov-
ing on a path parallel to the surface throughout one pass
(1). Avoid swinging the gun in an arc (2) or the finish will
be applied thinly at each end of the pass. Squeeze the trigger
just before each pass, and don’t release it until the spray
pattern is clear of the work at the other end (3). Aim the
center of the spray pattern at the edge of the panel. On the
return pass, overlap the previous application by about 50
percent (4) and continue with overlapping passes until you
have covered the panel with finish.
2 Swinging the gun produces an uneven coverage
me (e
3 Start and finish clear of the work
4 Overlap previous application on the return pass
pres EU
Spraying a horizontal panel
To spray a horizontal panel, such as a table top, spray the
edges first then work in parallel bands, aiming the gun at
about 45 degrees to the surface. Work away from you,
overlapping each pass as you do so.
Spraying legs and rails
Aim the gun at a corner to spray two sides of a leg or rail
simultaneously. Spray from the opposite side of the leg to
coat the remaining surfaces.
Spray enclosed
surfaces in sequence
Spraying inside
a cabinet or drawer
When you spray the inside
of a cabinet or drawer, be
systematic and concentrate
on spraying each surface in
turn to achieve even cover-
age. Spray the underside of
the top panel first, followed
by one side, always using
overlapping vertical passes.
Continue across the back of
the cabinet or drawer in the
same way. Then spray the
other side, and finally the
bottom surface. Spray the
outside after finishing the
interior.
293
A new approach to spraying — called High Velocity,
Low Pressure, or HVLP — is finding its way into
the woodshop. Here's why.
Traditional spraying uses a relatively small
amount of air under high pressure to atomize the
coating and transfer 1t to the work. The air com-
pressor usually requires a large storage tank to
provide a continuous supply of pressurized air.
HVLP takes a different approach. Instead of
a compressor, a single or multi-stage turbine
delivers a large quantity of air through larger
hoses at relatively low pressure. Working with a
spray gun designed for this air supply, you will
get a better coating of the suface, with less blow-
back, overspray and waste.
Costs of the two systems are roughly compa-
rable, and application patterns and gun-handling
techniques are very similar.
OIL AND WAX
Oil and wax are among the easiest wood finishes to
apply, no experience being necessary in order to
achieve first-rate results. Unlike varnishes and
lacquers that coat the surface, oil penetrates the wood
without leaving a film that holds brush marks or
other blemishes — and provided you use a fast-drying
variety, it does not form a sticky surface to attract
dust particles. Wax is used as a finish in its own right
SEE ALSO
Finishing on a lathe 199
Safety tips 284
Abrasive papers 285
Sanding sealer 286
French polish 288
a
and also as a dressing over varnish and lacquer.
® Restoring an oil finish
If the surface becomes
scratched or stained,
you can easily renovate
it — simply by applying a
dash of fresh oil.
Oil and wax polishes
1 Danish oil on iroko
2 Clear wax on oak
3 Antique wax on oak
WOOD-FINISHING OILS
Oil is traditionally used to treat naturally oily woods such as
teak and afrormosia, which tend to reject the majority of
finishes. But it is equally suitable for other hardwoods — and
even for softwoods, which it endows with a rich amber color.
Oil’s water-resistant properties are particularly advantageous
for exterior woodwork. Moreover, a subsequent application
nourishes oiled wood suffering from the effects of exposure to
the sun. However, it is not suitable as a finish for the interior
of drawers or cupboards, where it could stain the contents.
Linseed oil
Raw linseed oil is suitable
for small objects only. It can
take up to three days to dry,
by which time it may be
covered with fluff and dust.
Boiled linseed oil is margin-
ally better since it dries after
24 hours, but neither oil
forms a hard, durable finish.
Tung oil
Pure tung oil, also known
as China wood oil, is the
most durable oil finish. It
shrugs off water and is
resistant to heat and alcohol.
It takes 24 hours to dry, but
careful rubbing down with
very fine silicon-carbide
paper between coats will
produce a superb finish.
Apply five or six coats in all.
Danish and teak oils
Tung oil and other vegetable
oils usually form the basis of
a number of commercially
prepared finishes known
variously as Danish or teak
oils. Driers are incorporated
in these oils to shorten the
time between applications
to about six hours. Heat,
alcohol and water may
temporarily leave white
stains on the surface, but
they disappear quickly.
More permanent blemishes
can be effaced with a wipe
of fresh oil.
Salad-bowl oil
Most wood-finishing oils
contain toxic materials.
However, you can buy
non-toxic “salad-bowl oil”
for wooden counter tops,
chopping blocks and other
objects, such as bowls and
spoons, that come into
contact with food. Or, if
you prefer, use olive oil, or
other edible oils, instead.
WAXES
In the past, woodworkers
made paste wax by dissolving
a mixture of beeswax and
hard carnauba wax in turpen-
tine. These raw materials are
still available, but there are so
many excellent ready-made
preparations on the market
that most woodworkers do
not find it necessary to make
their own.
Wax makes for an attractive
mellow finish that seems to
improve with age. It is pro-
duced in a range of colors,
from practically transparent
for pale woods to deep brown
“antique polishes’ that create
the impression of an aged
patina and will disguise
scratches in a finished surface.
Silicones are added to
some polishes to make them
easier to buff, but if they
penetrate the wood, they are
difficult to remove and will
repel practically any other
finish should the workpiece
ever have to be restored.
Liquid or cream waxes
Liquid or cream waxes are
fluid enough to be brushed
onto the wood. Two or three
applications are required to
build up a protective body
of polish.
Paste wax
A paste wax, made to a
slightly thicker consistency,
is ideal for application with
a pad of very fine steel wool
or lint-free rag. On harden-
ing, it can be buffed with a
clean soft rag to an impres-
sive luster.
Woodturning wax stick
À stick of wax, hard enough
to be used as a friction
finish, is rubbed against a
workpiece spinning on a
woodturning lathe.
APPLYING OIL
Apply a generous coat of
Danish or teak oil to a clean
well-prepared surface with a
cloth pad or paintbrush.
Leave it to soak into the
wood for a few minutes,
then wipe over the surface
with a clean rag to absorb
excess oil. Six hours later,
apply a second coat and
leave it to dry overnight.
The next day apply one more
294
coat, and buff it to create a
sheen.
It takes longer to finish a
surface with pure tung oil.
After the initial coating,
applied liberally with a
brush and rubbed over as
already described, apply
several thinner coats to
allow the oil to dry between
applications. If dust par-
ticles adhere to the surface
during the 24-hour drying
period, rub it down lightly
with very fine sandpaper in
the direction of the grain.
APPLYING WAX
Although you can apply
wax directly to bare wood,
it 1s an advantage to seal the
surface first with a varnish
or, for superior-quality
work or oil-stained wood,
with two coats of shellac
sanding sealer or white
French polish. Sealing pre-
vents the initial coat of wax
from being absorbed too
deeply into the grain,
especially when you are
using a liquid wax. It also
prevents dirt from sinking
through the wax and
permeating the wood over
a period of time.
Having flattened the sealer
coats with very fine silicon-
carbide paper, if you are
using a liquid wax, apply
the first liberal coat with a
brush or use a soft cloth pad
to rub it into the wood with
circular strokes first and
then straight ones in line
with the grain. One hour
later, buff up the wax and
apply a thin coat with the
pad in the direction of the
grain only. Add a third coat,
if needed, similarly and buff
it as before. Leave the wax to
harden for several hours,
then burnish the surface
vigorously with a clean soft
rag.
If you decide to use a paste-
wax polish, apply it with a
pad of 0000 steel wool,
rubbing with the grain only,
and bring it to a shine with a
soft cloth.
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