الفهرس 
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Abstract
Varnish is a liquid coating material containing a resin, solvents and
driers that dries to a hard transparent film.
Most varnishes are a blend of resin, drying oil, drier and volatile solvent. When varnish
dries, its solvent portion evaporates, and the remaining constituents oxidize or polymerize to
form a durable transparent film. The early varnishes were solutions of natural resins that are
the secretions of plants. Among these natural resins are dammar, copal and rosin. The
natural varnishes are produced by heating the resins, adding natural oils such as linseed oil,
cooking the mixture to the desired viscosity and then diluting it with turpentine. The
resultant coating took three to four days to harden, had a yellow tint and eventually
developed cracks as it aged. Natural varnishes have largely been replaced by varnishes
containing synthetic resins, chief among which are the alkyd, polyurethane, phenolic, vinyl
and epoxy resins. Phenolics continue to be used in marine and floor varnishes. Alkyds are
made with an alcohol such as glycerol, a dibasic acid, such as maleic or phthalic acid, and
oil, such as castor, coconut, linseed, or soybean, or a fatty acid. Unlike natural resins,
synthetic resins can be manufactured in large quantities and can be chemically tailored with
great precision for particular uses. For example, the molecular structure of alkyd resins can
be manipulated to vary with viscosity, their hardness, their solubility in water or other
substances, and their capacity to mix successfully with various pigments. Varnishes consist
mainly of binder i.e. a carrier and solvent, both will be discussed below.