Pastel Chalks
2003-4-24
Chalk pastels are made by compressing powdered pigments to form hard sticks of colour. Perhaps for this reason they are often referred to as hard pastels. They should not be confused with the softer, waxier pastel "crayons".
Typically, model makers employ pastel chalks in one of two ways. Before doing so, however, they must return the stick back to into its powdered form. This can be done by rubbing the stick against very fine sand or emery paper. This will produce a fine dust which can be collected in a suitable receptacle.
In this state, the powder can can be applied "neat" with a soft brush. By employing a dust in this manner means you are equipped with the perfect medium with which to replicate dusty deposits and other residue. Black chalk, for example, is perfect for portraying sooty stains around exhausts or blast marks around impact points. The dust can be dabbed on with a brush - or even a cotton bud - and then blended "out" into to the surrounding paint work. Browns and other muddy colours can be used to represent dirt and other muck on wheels and under carriages, etc. Orange powder, if used in moderation, makes excellent rust - especiallly when applied to features such as chains or other old iron work.
Modellers also use chalk powder to provide definition. If applied (with a deft hand) along panel lines, it can be used to enhance shadows by making deep recesses appear even deeper. This fools the eye into believing it is seeing far more relief than is actually present. The same technique can be used where any two surfaces meet at a steep angle.
The second method of using pastel chalks has been made fashionable by modellers in the far east. After reducing the chalk into a powder it is mixed with a carrier medium - such as Tamiya Acrylic Thinner (ref# X-20A). The resulting mixture is then applied with a brush like a paint. After a while the thinner will evaporate leaving the chalk powder in place. This technique is sometimes used to accentuate bolt heads, rivets and such like.