Gypsum is one of the most widely used materials not only in construction, but also in art, in dental technology, in the jewelry industry, etc.
The quality of gypsum products is primarily determined by the choice of gypsum powder and careful adherence to the technology for preparing the solution. It is quite possible to make a plaster cast at home.
This material has been used since ancient times, before the invention of machines and electricity. All that is needed for preparation is dry gypsum and water, a container for preparing the solution, a spatula for stirring. It is also good to have a fine-mesh sieve (0.2-0.5 mm) for sifting dry gypsum before preparing the solution. Fresh gypsum of good quality in its original packaging does not require pre-screening. For modeling, there is now a wide variety of kits on sale, which, in addition to plaster powder, include tools for working with plaster.
The basic requirements for the process of obtaining a gypsum solution are the same for all types of gypsum and methods for obtaining a solution - the powder is poured into water, stirred with a spatula, avoiding the formation of air bubbles in the solution. You can pour it in a thin stream, while stirring the solution (in this case, foam may form on the surface that needs to be removed) or pour it into the middle with a mound and stir with a spatula with cutting movements inside the liquid volume, without trapping air during stirring. In industrial conditions, evacuation is used to remove air from the solution.
It is impossible to delay the cooking process, you need to have time to make the plaster cast in 1-2 minutes. The consistency should be the same as heavy cream or sour cream. Usually, 1 kg of powder is poured into 0.7 liters of water. Too liquid solution will lead to a decrease in the strength of the products, too thick - poorly fills all the corners and convolutions of the form.
Dry gypsum can be added to the solution to obtain the desired consistency, but the gypsum cannot be diluted with water. Also, you cannot use a vessel with the remnants of the previous portion of gypsum to prepare the solution.
Depending on the brand of gypsum, the solution hardens in a time of 5 to 30 minutes, so you need to mix it in small portions, which will be used in a limited hardening time. It is possible to work with the solution during the period from the beginning of setting to hardening. Next, the product must be left in a warm room to dry. Low temperatures have a negative effect on the quality of plaster products.
