School chalk is of two main types: lumpy and pressed. Natural chalk used for the production of school crayons is mined in quarries or extracted from rock. This raw material is absolutely safe, non-toxic and does not contain impurities. The pressed chalk is based on calcium sulfate, which is obtained from gypsum. For the manufacture of school chalk of a certain form, starch and limestone are used. Lumpy natural chalk is almost entirely composed of calcium carbonate. Sorted natural chalk is used to produce school chalk.
Colored crayons are produced by a similar technology with the only difference being that various dyes are added to the mass during the production process. The manufacture of chalk for drawing and writing on boards and on asphalt includes several main stages: grinding of raw materials, settling of heavy impurities, drying on a grate, adding adhesive, molding.
For the manufacture of the highest quality crayons, elutriated chalk (or, as it is also called, fused) is used. To prepare elutriated chalk, natural chalk is broken into pieces, sorted, impurities are removed, and then ground with water on millstones. The resulting mass settles, with the result that heavy impurities (sand, stones) are deposited at the bottom of the tank. Then a liquid with a cleaner feed is passed into the second and then into the third tank until all impurities are at the bottom of the tank and removed. The remaining chalk solution is left for several hours to settle, after which the water is drained, and the remaining mass is transferred to boxes with perforated walls, which are covered with a cloth. Then the mass is dried on a wire rack. If the chalk crumbles during drying, then a small amount of a solution of dextrin or glue is added to it. Recently, so-called non-crumbling crayons without dust have become increasingly popular. They are made using special technology using casein. The main difference between such crayons from ordinary ones is that they do not get dirty hands and clothes when used.
Colored crayons should also have a certain hardness. However, when dyes are added to the chalk mass after drying, the chalk becomes too friable. Therefore, in the manufacture of colored chalk, chalk powder is mixed with a certain amount of mineral paints to obtain the desired shade and mixed in an aqueous solution of wood glue, gum arabic or dextrin. In principle, you can use any mineral paint, but keep in mind that when mixed with chalk, some colors are distorted (for example, bakan, Prussian blue and chrome yellow). Colored crayons can be used not only for drawing on asphalt (in this case they should be very hard), but also for writing on the board. To give the crayons greater softness, they add a soap solution, oil or wax. Ready and dried crayons are immersed in oil, which improves their color and gives them great softness. A mixture of chalk, coloring matter and a binder is laid out on a flat surface that is pre-coated with several sheets of paper. Paper absorbs a large amount of moisture, resulting in a chalky mass acquires a thick consistency. When the mass becomes sufficiently thick, a piece the size of a nut is taken from it, and then it is rolled into a cylinder. At the last stage of molding, the cylinder is rolled with a smooth plate to give it a flat surface. Finished crayons are laid out on the boards, covered with paper and dried at room temperature.
This technology is considered quite expensive due to the large amount of manual labor. To reduce the cost of production, crayons are made from a mixture of light clay, water and chalk, to which dye is then added - ultramarine (for blue crayons), mummy and cinnabar (for reds), ocher (for yellows), etc. The whole mass is uniformly mixed and It is transferred to special wooden or metal forms, pre-greased with fats. After molding, the pieces of chalk are removed from the molds and left to dry in air or in a poorly heated room.
In addition, crayons can be made by grinding rubbed chalk with calcined gypsum (which does not set when wet) and steatite. Then mineral paint is added to the mixture, and it is mixed with a weak solution of dextrin. The mass is placed on filter webs to remove excess moisture. The dried mass is cut into prisms of the desired size and left on gypsum plates for drying, from time to time turning them on the other side.
The degree of drying of the chalk and its composition determine the hardness of the product. Harder chalk is used for drawing on asphalt, chalk of medium hardness is used for writing on blackboards, and soft chalk is used for tailor's work.
For the production of white and colored crayons in such ways, complex expensive equipment is not required. The total cost of acquiring everything necessary for production will be about 50 thousand rubles. In addition, cardboard packaging is needed for the packaging of finished crayons (white crayons are usually packed in bulk boxes of 100 pcs., And colored ones into small boxes of 6-12 crayons). The total cost of organizing a small production of chalk is from 100 thousand rubles (including the purchase of raw materials). Finished products are delivered to stationery stores, shops for goods for children's creativity, specialized stores for schools, as well as directly to public educational institutions.
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