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The following are a small selection of helpful hints and tips from our book The Finishing
Touch. The book is a mine of information from which even the most experienced model painter
can glean something new.
Always mix your paints thoroughly using either a spatula for hand mixing or a power mixer.
Shaking the can or stirring with an electrical type screwdriver or similar shaped object is
useless.
When opening a tin of paint always clean the rim as any dust will be sucked into the tin
when the lid is opened.
If you buy a number of tins of the same colour paint mix each one thoroughly then mix them
together in a larger container. Finally put them back in their original tins. This will
ensure you have an identical shade in each tin. The original tins may have been from
different batches.
ALWAYS buy sufficient paint for the whole job.
Degreasing
A lot of so called 'experts' advocate the use of washing-up liquid and hot water for
degreasing. Don't EVER use this method. Washing up liquids always leave a film on the
surface which enamel paints do not like. Even Etch Primer will not work properly if this
method of degreasing has been used. Always use a solvent. If the model is plastic, then the
strongest solvent you can use is White Spirit or Turps Substitute. If the model is able to
stand it we recommend the use of cellulose thinners as the de-greasant. It is the strongest
solvent commonly available.
If the model consists of different kinds of material such as plastic and metal, use an
overall coat of matt or eggshell paint to give a uniform finish. Then apply a coat of white
primer or undercoat. The use of white is recommended as we always match colours on a white
background.
Brass, copper, aluminium and nickel silver, in fact all non-ferrous metals should be etch
primed before applying any subsequent coats of paint. These metals have an oxide layer which
paints do not adhere to very well. Even if abraded with abrasive paper, the oxide layer
reforms within 2 or 3 seconds!! Etch Primer has an acid in it to microscopically eat through
the oxide layer and into the metal thus providing a key for the paint.
It does not matter where or who you buy your etch primer from, you MUST use the special
thinners for either thinning for spraying, or for cleaning your brush or spray gun. Single Pack Etch Primer is the same kind of material whoever makes it. Ordinary thinners will not work and you could end up ruining your spray gun - not because the parts have been etched but because the primer has gone through a chemical change that is irreversible and so cannot be cleaned out. Single Pack Etch Primer does not etch until it is dry so will not harm your equipment under normal usage.
An instruction sheet is provided with every tin of Precision Paints Etch. Follow them. They
are there to help you get the best results possible. If your Etch Primer does not stick then
you have done something wrong!
For ferrous metals use either Rust Stabilising Primer or or 2 Part Etch Primer. For stainless steel use Red
Oxide. The acid in Etch Primer is not strong enough to etch stainless steel.
Painting
When painting with a brush always use the appropriate size and shape. Trying to paint a 5"
gauge loco with a No.6 brush will result in a very uneven finish. For such large surfaces
use a 3/8" or 1/2" flat sable brush. (See our catalogue for a full range of suitable brushes)
When cleaning a sable brush use clean thinners and when clean suspend the brush to dry with
the hairs downwards. A 1/16" (2mm) hole drilled through the handle will accommodate a thin
wire to hang it up. When dry moisten the hairs and reshape using the fingers and saliva.
Allow to dry naturally. This is the best way to preserve the shape and condition of a sable
brush.
When brushing apply a coat of paint in one direction, brush it out at 90 degrees to the
original direction using a lighter stroke. Finally brush in the original direction with a
very light stroke. With practice you will be able to achieve a brush-mark free finish.
If you apply a Dull or Matt finish and the paint dries with streaks of gloss in it, you have
not mixed the paint thoroughly enough.
Spraying
When buying an airbrush for painting models, it is wrong to expect the most expensive to
give the best results. Airbrushes were originally designed to spray ink by graphic artists.
Paint being a lot thicker will not produce satisfactory results from the expensive
airbrushes due to the fine nozzles. For a good all-round airbrush we recommend either the
Badger 200 or the DeVilbis Sprite. Both of these can be used for painting 4mm scale up to
5" gauge models. For anything larger, a miniature spraygun such as the Kite is
recommended.
Just because you have an airbrush, don't expect an exhibition class finish the first time
you use it. Practice - practice - practice.
Airbrushes can be powered by aerosol cans of propellant, car tyres or compressors. The only
power source we recommend is a compressor. The main problem with aerosol propellant is that
they freeze after a few minutes spraying. You then have to wait ages for them to thaw out
to attain full working pressure again. With a car tyre the problem is that the pressure
starts off high but then decreases as you use the air so you have to keep stopping to pump
it up. A compressor will provide a constant supply of air at constant pressure. As
compressors start to generate water vapour after about 20 minutes running a water trap is
essential. For airbrush use a miniature water trap should be used such as is made by Spirax
Sarco Ltd of Cheltenham. These can be supplied together with a miniature pressure regulator
and gauge. The water trap must be at least 3 feet (1000mm) from the outlet of the compressor.
This will allow the water vapour to condense in the line so that the swirling action of the
water trap will throw out the water droplets by centrifugal force. The condensate can then
be bled off as necessary by the valve in the base of the water trap.
Always thin the paint to be sprayed. The amount of thinners depends mainly upon the pressure
you have available. The higher the pressure the less thinners are required and the lower the
pressure the more thinners are required. Start off with a mix of 1 part thinners to 3 parts
paint. Always use Quick Air Drying Thinners for spraying as they dry about 6 times faster
than White Spirit or Turps Substitute.
Airbrush manufacturers recommend spraying from 12 inches (300mm) This is much too far away.
In most cases the paint will have started to dry before it reaches the surface and this will
give a patchy and more matt finish. You should be using about 30 p.s.i. and spray from about
4 to 6 inches (100 to 150mm). The exception to this rule is Etch Primer which must be
sprayed at NO MORE than 15 p.s.i. and from a distance of only 2 to 2.1/2 inches (50 to 65mm).
If the Etch Primer emerges from the spray gun as a mass of fine hairs, you need more
thinners and/or reduce the pressure further. The problem is that the primer is prematurely
starting to dry in the nozzle.
When spraying varnish, especially Satin or Matt varnish, DO NOT use quick drying thinners.
Use a slow drying thinners such as our PS10 Varnish Thinners. The problem with quick drying
thinners is that the varnish does not have time to flow on the surface and it will take on a
milky appearance. This is the same effect as ground glass being white rather than
transparent. All varnish coats MUST be allowed to flow on the surface.
How often have you finished a painting job and then seen a small wiggly blemish in the
coating. This is the result of wearing the wrong clothes. Never wear anything which contains
wool when painting. Even cotton garments can moult fine fibres into the air. The best way to
prevent these blemishes is to wear one of the 'throw-away' cover-alls obtainable from safety
centre shops. Look in your Yellow Pages for addresses. Alternatively a nylon coverall can be
worn if you can find one.
Having painted the model, cover it with a box, but not completely. Allow at least 2" (50mm)
gap to enable the solvent vapour to dissipate as it is heavier than air. If you don't leave
the gap the paint will take much longer to dry - maybe days!!
Lining
FINALLY...........................................WHEN PAINTING ANYTHING, DON'T BE IN A HURRY!!!!!!!!!
Good luck.
Bob Shephard
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