Varnish is the solution of resins or resinous substances like amber, copal, shellac, gum resin etc. in solvents like oil, turpentile, alcohol etc. Depending upon the solvents used varnishes are classified as, oil varnishes, turpentile varnishes, spirit varnishes and water varnishes.
Properties of Varnish:
- It is combination of a drying oil, a resin and a thinner or solvent
- Glossy but may be designed to produce satin or semi gloss sheens by adding of flatting agent
Components of classic varnish
There are many different types of drying oils, including linseed oil, tung oil, and walnut oil. These contain high levels of polyunsaturated fatty acids.
Resins that are used in varnishes include amber, kauri gum, dammar, copal, rosin (pine resin), sandarac, balsam, elemi, mastic, and others. Shellac is also a resin. In the 1900s in Canada, resins from local trees were used to finish pianos. As a result, these now antique pianos are considered difficult to refinish. However, shellac can be used over the existing resins provided sufficient time is allowed for thin coats to cure. Thus the original finish can be returned to its original lustre while preserving the color and age-related crackle.
Solvent (traditionally turpentine)
Traditionally, natural (organic) turpentine was used as the thinner or solvent, but has been replaced by several mineral-based turpentine substitutes such as white spirit or “paint thinner”, also known as “mineral spirit”.
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