The Cool Tool UNIMAT 1 Manual Del Usuario página 30

SURFACE TREATMENT OF WOOD
Especially with wood, surface treatment (san-
ding and painting) is very important. Natural mate-
rials initially have a very beautiful surface which in
the cause of time easily becomes "shabby" (e.g.
water marks).
SANDING:
When sanding by woodturning, the workpiece
should be fixed. First it is sanded with grain 150 and
then with a finer paper.
Press the sanding paper on to the rotating work
piece and keep on moving to the left and to the right
in order to avoid grooves. After the sanding you can
"polish" with saw dust.
Sanding tips for other woodworking techni-
ques:
Hold sanding paper evenly and use, if
possible, a sanding block. Work with the fibre,
never against it. Keep the sanding paper dry,
damp ness soaks up the glue and that can ruin your
work. Glasspaper quickly loses its sharpness,
garnet-paper is more expensive but lasts much lon-
ger. After the final sanding stage wet the wood.
This way the fibres will erect, then sand off these fine
"hairs" with fine sanding paper.
Also after the first painting you should again
finish the workpiece with fine sanding paper (800)
to receive a smooth, beautiful surface.
Furthermore: The graining gives you the
amount of grains per unit area, sanding paper 800
is therefore 4 times as fine as sanding paper 200.
28
HANDBOOK
STAINING:
Staining means colouring wood without covering
its natural structure. It does not protect the surface
and therefore the wood should be lacquered after it
has been stained. According to the solvent there exist
water stain, oil stain, spirit stain and chemical
stain. As a beginner in model making you should
start with water stain, as it is cheap, colourproof, non-
poisonous, and it is easy to apply. They are offered as
powders and can be mixed to suit your requirements.
To begin with apply the stain generously with a brush,
sponge or lint-free cloth and rub it thoroughly imme-
diately afterwards with a clean (and also lint-free)
cloth. If you do not apply enough stain or you apply
it too slowly it will develop an uneven surface. Before
lacquering (sealing) leave the work piece to dry for at
least 2 hours.
Tips for staining:
First try the staining shade on a leftover piece
of wood. Apply the stain generously. Too little
stain will produce marks, therefore it is advised to
mix enough stain before starting. Always work with
the grain (when applying and rubbing). Sand the
surface only after it has been sealed, otherwise
it can lose colour.
BEESWAX:
Beeswax is offered as paste and is the most
"natural" way of surface treatment. Although it does
not give the same wood protection as for instance oil
or lacquers (see page 26). The wax should be rubbed
into the wood with a soft cloth. This must be carried
out very carefully in order to prevent stains.
OIL
Oil is a natural way to seal wood. It has the
advantage of protecting the surface, it leaves the grain
beautifully visible and the wood keeps its "warmth"
when you touch it. The oil is applied generously and
quickly, left to dry for a short time and then rubbed
completely dry with a clean cloth. Sand off the "hair"
with fine sanding paper and repeat the procedure.
Two applications are generally sufficient. Shortly
before the wood is completely dry, sand it gently
once more with sanding paper grain 1000.
INSOLUBLE COVERINGS
These are all modern lacquers and two-compo-
nent products. They harden in two steps. First the
solvent evaporates (the resulting surface is now suffi-
ciently hard to continue with further processing). The
second hardening stage happens through a chemical
process whereby finally a new substance has develo-
ped. This process can last up to 10 days. These pro-
ducts are widely used in industry and trade. Applied
with spray pistols or other technical appliances they
leave a long-lasting surface.
Tips for use in your own workshop:
Do not brush on hard but rather let the lacquer
flow over the surface. Use a lot of water when working
with wet sanding paper, be careful with edges. Work
in a dustfree environment with sufficient airing, wear
an overall. Clean the brush immediately after use, buy
thinner and lacquer from the same supplier.