At first the available colors are ground on a stone slab (by rubbing or grounding) to bring them in a powder form. Some artists use mortar and pestle of a very hard quality stone. Then that color is dissolved in water along with some gum and then filtered. The filtration process is continued till the color becomes totally earth or sand free. Thereafter water is removed and the color is dried and kept in form of balls. When required, the desired color along with some dry gum is dissolved slowly in water with the help of finger or thumb. The color is now ready.
By dissolution, the color starts getting thicker and gains the consistency of a paste and then pressure is required to be applied. The color gets well mixed from the strength applied at this time. This process is termed as tempering. Thus this process is termed as Tempera. If the color is once allowed to get dry and then made thinner as per requirement by adding water then it gives better results.
The colors used in painting can be divided into four main groups:
- Earth or mineral colors
- Vegetable colors
- Oxide colors
- Metal colors
Earth or Mineral Colors
Colors available in the form of stones come under this category. For example consider the color black . Black is a basic color. A sand lamp is placed over a lighted lamp till black soot or lamp black "kajal' is obtained therefrom. Babul gum, Acacia resin and water are added to this kajal and ground slowly with the first finger till it gets tempered to obtain a fine black color. Black ink is also prepared at Jaipur in this manner. The only difference in the writing ink and black color is that the former has more gum than the latter. color prepared from the soot of a lamp using mustard oil, though being a watercolor, is unassailable by water after it has dried on the paper.
The colors obtained from different parts of trees or plants come under this category. For example the preparation of Red color from the bark of the peepal tree. The bark is immersed in water and cleaned. Then it is crushed along with borax -suhaga and heated in an iron pot. This makes the color come out. This color can be preserved in cotton wool or it can be kept secure by concentrating in tablet form.
Oxide or Chemical Colors
These are obtained by burning, pulverizing or mixing various materials by chemical process. For example consider the emperor of all green colors, the Jangal color. Copper powder one ser (One ser = 900 gms. approx.) and Nausadar (sal-ammoniae) two ser both should be kept in a copper pot. Lime juice should be squeezed into it till it is two fingers (about one inch) above the medicine(material in the pot). The mouth of the pot should now be covered by a cloth. It should be kept forty days in that condition. The material should then be ground in the same juice and then dried up in shade. Good quality Jangal will result. Whenever required, it should be mixed with glue to use. Gum doesn't suit this color.
The fine powder of gold, silver and lead have been used in paintings as well as mica pieces. It can be ground and applied like other colors. Gold leaves are used in two ways. In the first process, the leaves are pasted directly. For this a mixture of glue and sugar is applied at the required spot in the required size. Thereafter the gold leaves are pasted, moistening it with mouth vapours in between. Minute and fine work is done by means of golden or silver powder specially prepared. It is called Hilkari in local dialect. To prepare Hilkari, a thick paste of gum, glue or honey is applied on a metal plate. The gold leaf is pasted over it and it is rubbed with the help of four fingers or the palm in a rotating manner. By doing so, the leaves turn into a fine powder. It is necessary that the paste on the plate should be thick. If the paste is thin then the gold leaves would turn into balls. This finely ground gold powder is transferred to a tumbler gradually and simultaneously with water. In the end the whole glass is filled with water and the Hilkari. It is left as such for 24 hours and then the water is drained off. The gold or silver settles at the bottom. When required, it may be applied after mixing a small quantity of gum. On rubbing agate stone over it, that part begins to shine like gold. With Hilkari the quantity of gum should not be much otherwise the gold would not shine.