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size, a sticky solution prepared by heating an aqueous suspension of potato starch (to 70 °-75°C) or cornstarch (to 80°-85°C). Paste is used to glue paper to cardboard, wood, and other materials, in house painting and paper hanging, and in bookbinding. For finishing textiles, paste should contain 6–10 percent starch.
(in medicine), a doughlike ointment that contains a minimum of 25 percent powdered components. Pastes have adsorptive and drying properties and are used as anti-inflammatories.
Protective pastes shield the skin from harmful chemicals or physical irritants, for example, organic solvents; aqueous solutions of acids, salts, and bases; and ultraviolet rays. All protective pastes must meet specified requirements. They cannot contain substances that irritate, sensitize, or disturb the physiological functions of the skin, and they must be easy to apply and remain firmly in place, during motion. Ordinary washing, without the use of special solvents, should be sufficient for their removal, and they must be insoluble in substances that harm the skin. Protective pastes are manufactured from starch or soap bases to which other compounds are added, for example, fats, oils, or organosilicon polymers, depending on use.
a multicomponent mixture or a pure substance with viscous, plastic properties or with elastic, viscous, and plastic properties. Pastes retain their shape but under stress flow as viscous liquids.
A distinction is made between homogeneous pastes, which consist of a single phase, and heterogeneous pastes, which consist of two or more phases. Heterogeneous pastes, which are concentrated, disperse systems in a liquid dispersion medium, are the most common. They are usually obtained by dispersing solids in an appropriate wetting agent. In many cases, surfactants are added to facilitate dispersion and to impart desired properties to the paste, for example, homogeneity and enhanced or reduced plasticity. Pastes are also prepared by simply mixing a powder with a liquid. The dispersed phase constitutes up to 70–80 percent of the matter in a paste, and the contacts between the particles of the dispersed phase are of the coagulation type (seeDISPERSE STRUCTURE).
Many building materials and paints are used in the form of pastes, for example, mastics, putties, plasters, spackling compounds, and primers. Other substances that are supplied as pastes are polishes and abrasives, molding compounds in the production of ceramic and plastic parts, pharmaceutical and cosmetic preparations, food products, and inks for ball-point pens. Pastes are easily transported and readily modified.