The three ingredients of a varnish are: resins or resinous substances, solvents and driers.
1. Resins
As stated earlier, the commonly used resins are copal, lac or shellac and resin. Copal is available from the earth at places where pine trees existed in the past. It is a hard substance in a variety of forms. Lac or shellac is obtained by the exudation of some insects. Resin is obtained from pine trees.
2. Solvents
Based on the type of resin, the type of solvent is decided. Table 12.1 shows the solvent for different resins.
Table 12.1 Solvents for different resins
3. Driers
To accelerate the process of drying, driers are added to the varnish. Common driers used in varnishes are litharge, white copper and lead acetate.
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