Potassium silicate is the name for a family of inorganic compounds. The most common potassium silicate has the formula K2SiO3, samples of which contain varying amounts of water. These are white solids or colorless solutions.
Potassium silicates are manufactured using a calcination process that combines silica sand (SiO2) and potassium carbonate (K2CO3) at 1100-2300°F for up to 15 minutes. The two substances fuse into glass, which can be dissolved with high-pressure steam to form a clear, slightly viscous fluid, or cooled and ground into a powder. Carbon dioxide is evolved from this reaction. The solution can be dried to form hydrous powder crystals or liquid of potassium silicate.
Woodwork protection against fire
Impregnation of wood with a potassium silicate solution is an easy and low cost way for rendering the woodwork of houses secure against catching fire. The woodwork is first saturated with a diluted and nearly neutral solution of potash silicate. After drying, one or two coats of a more concentrated solution are usually applied.
In horticulture, potassium silicate is used as a soluble source of potassium and silicon. It makes the growing medium more alkaline.
It is also used as a supplement (in conjunction with normal fertilizer) for the numerous benefits that increasing the availability of silicon compounds has. Silicon-containing compounds are valuable to a plant, and serve to support the plant. Stems thicken, the plant becomes more tolerant to drought and resists wilting, and the plant gets larger leaves and fruit (because the stem can support more weight). The thicker cell walls of the plant also provides an added mechanical resistance to sap sucking insects (e.g. spider mite) and various pathogenic fungi (e.g. powdery mildew).
Some metal cleaning formulations use potassium silicate, which also serves as a corrosion inhibitor. It also finds various uses in the fabrication of welding rods or even of cosmetics.