AS LETTING GROW CRYSTALS
If we dissolve a little water salt and soon we let evaporate the solution, salt returns to crystallize, returns to the solid state, although probably the crystals that form are very small and imperfect. Other salts that can be obtained easily (in a pharmacy or an ironworks), with which exist we can try to obtain well formed great crystals and. Two of those salts are the sulphate of copper (a blue substance that is used to disinfect plants) and common alum (double sulphate of aluminum and potassium).
SINCE ONE BECOMES
Copper sulphate: To grind the substance until obtaining a fine powder (to accelerate the dissolution). In a glass bottle (as the used ones for jams, instantaneous coffee, etc.) to half spill some 8 flat spoonfuls of worn out copper sulphate (approx 70 or 80 g) and glass of water (approx 100 ml). To place the bottle within a broad pot or with water and to warm up to boiling (bathroom of Maria), maintaining about 15 to 20 minutes. Salt will dissolve until the solution is saturated, being a rest of salt without dissolving. Taking care of not burning the fingers, in the heat of the moment filtering the solution through a cotton piece, fine fabric or filter paper for coffee, to another clean bottle. To let rest the limpid solution in the bottle covered with a paper in a calm corner. Soon after (hours or days, according to the degree of saturation of the solution) small blue crystals will begin to form, that will be growing with running of the days, reached some cm of length.
As improving the growth of crystals:
In order to obtain more perfect crystals, to tie a crystallite with a fine thread or a hair and to suspend it in a saturated solution and it fries. The crystal will grow slowly, showing expensive and defined angles good.
If a thread of cotton in the saturated solution submerges (leaving an end in the edge of the bottle) will form a chain of crystallites throughout the same.
Common alum: To come as before, but dissolving 3 or 4 flat spoonfuls (about 30 g) of good alum ground glass of water in the middle. The alum easily forms beautiful colorless crystals with form of octahedrons (as if they were two pyramids of Egypt united by the bases).