The pure pigment is ground into very fine powder and then mixed with a medium, usually gum tragacanth or a similar resin to bind them together.
A filler, usually clay or white chalk, is added to the mixture of pigment and binder. This creates a paste, the word from which pastel got its name.
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Filler is used for making the wide range of shades of pastel colours. The greater the amount of chalk that is added the lighter the shade. Those with more chalk are cheaper to produce. Black is also added so that a full range of shades is produced. |
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You can purchase Pastels that are either mechanically produced or hand-made: Machine made pastels are made by mixing pigments with water, gums, and other additives in large mechanical mixers. The pastel dough is then pushed through the barrel of an extruder by a long revolving screw. The solid dough is forced through a circular opening at the extruders end. It emerges from the extruder like a long pencil and is cut to stick lengths. It drops onto a conveyer belt to go through a drying operation, then a wrapping operation. The problem with extrusion is that it squeezes the pastels very tight and compresses them. This makes them hard, on the whole and it alters their consistency and response to being used. |
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Hand made pastels on the other hand hardly get pressed at all. They are rolled very gently and this makes them very fluent to use. Unison pastels are hand made and many of the colours are pure and single pigments. Many pigments will hold together after being mixed with water, rolled and dried and for those that fall to pieces a little weak starch or gum is added to give the best response without interfering with the colour. On the whole they are blended, three, four or five different pigments together and very little white or chalk is used. Artists are looking for intense and dark pastels and the best are pigment and nothing else. |