Wasserglas

Wasserglas, known in English as water glass, is an aqueous solution of silicate salts, most commonly sodium silicate (Na2SiO3) or potassium silicate (K2SiO3). The liquid is clear, viscous, and highly alkaline, typically with a pH around 11 to 13. Commercial products vary in the silica-to-alkali ratio and degree of hydration, and are often described by the modulus SiO2/Na2O.

Production and composition: Wasserglas is produced by dissolving silica in a strongly alkaline medium, such as sodium carbonate or sodium hydroxide, to form a sodium silicate solution, which is then diluted with water. The resulting solution contains polymerized silicate species with surface-active properties. Upon drying, the solution can form a glassy film, which explains the name water glass.

Chemistry and behavior: The solution consists of silicate ions that can polymerize to form a three-dimensional network. When concentrated, heated, or acidified, the silicate can gel or precipitate silica, strengthening a coating or binding matrix. Dried films are relatively water-resistant and often adhere well to porous materials.

Applications: Wasserglas is used as a binder and sealant in ceramics, casting, and foundry work; as a consolidant and protective coating for porous building materials such as stone and brick; and as a preservative or fixative in conservation and crafts. In traditional practices, it has been used to coat eggs to reduce porosity and extend shelf life. It also serves as an adhesive for paper, textiles, and wood in some craft contexts and laboratory settings.

Safety and handling: Wasserglas is caustic and highly alkaline, and contact with skin or eyes should be avoided. It should be stored in tightly closed containers away from acids and moisture, with disposal conducted according to local regulations.