Sodium silicate, also known as water glass or soluble glass, is a compound containing sodium oxide and silica. The viscosity of this compound varies according to the ratios of silica and sodium oxide used. This alkaline substance is available as a nearly colorless, glass-like powder, or as a syrup-like liquid when mixed with water and heated under pressure. Sodium silicate has a variety of industrial, agricultural and manufacturing uses.
Sodium silicate is used in liquid form as an adhesive in manufacturing applications. It is used to bind items such as paper cores for paper towels and toilet tissue, fiber drums, corrugated board, paperboard laminates and angleboard. The liquid sodium silicate is typically applied via a transfer roller, by cascading the diluted solution on the material surface or by immersing the material in the adhesive solution. Some manufactures prefer sodium silicate as an adhesive because it is low cost, non-toxic and environmentally friendly.
Potters and ceramics manufacturers use sodium silicate as a deflocculent, which is a thinning substance. This compound is added to slip, which is a thin liquid clay used to attach pieces of unfired ceramics, or greenware. For example, a potter would coat the edges of a cup handle before attaching it to the cup. The addition of sodium silicate reduces the amount of water needed to make the slip, so there is less shrinkage during the firing process. As a result, fewer pieces are destroyed during firing. Sodium silicate powder must be mixed in a 1 to 1 ratio with water for this application.
Silica Gel Production
Sodium silicate is one of the raw materials used in the synthetic production of silica gel. Silica gel is an effective dessicant, or drying agent. Although the name suggests that silica gel is a pliable substance, it is actually made up of irregularly-shaped hard crystals. It has a high surface area by weight--800 square meters per gram--and is microporous, which allows the substance to draw in and trap moisture. Manufacturers add moisture-sensitive dyes to some types of silica gel--these dyes change color as moisture is absorbed into the pores.