Varnish

Definition - What does Varnish mean?

Varnish is a type of paint with a solvent that evaporates to leave a hard, transparent, glossy film. Varnish is primarily used in wood finishing but can be for other materials as well. It is traditionally a combination of a drying oil, a resin and a thinner or solvent, and is employed for protection against deterioration and corrosion.

The advantage of varnish is its very rapid cure rate compared to oils; in most cases they are cured nearly as soon as the solvent has fully evaporated.

Corrosionpedia explains Varnish

Varnish is a preparation consisting of resinous matter dissolved in oil (oil varnish), alcohol (spirit varnish) or another volatile liquid. When applied to the surface of wood, metal, etc., it dries and leaves a hard, more or less glossy, usually transparent coating.

Varieties of varnish include:

  • Resin varnish - Consists of a natural, plant- or insect-derived substance dissolved in a solvent, called spirit varnish or solvent varnish. Shellac is a widely used single-component resin varnish that is alcohol-soluble.
  • Spar varnish - Originally intended for use on ship or boat spars, to protect the hull from the effects of sea and weather
  • Polyurethane varnish - Typically hard, abrasion-resistant and durable. It is popular for hardwood floors.
  • Acrylic varnish - Typically water-borne varnish with the lowest refractive index of all finishes and high transparency
  • Lacquer - Quick-drying, solvent-based varnishes or paints

After application, the film-forming substances in varnishes may harden immediately, as soon as the solvent has fully evaporated. Otherwise, they may need to undergo certain curing processes, primarily chemical reactions between oils and oxygen, and chemical reactions between components of the varnish.

Environmental factors such as heat and humidity play a very large role in the drying and curing times of varnishes. The drying and curing time of all varnishes may be sped up by exposure to an energy source such as sunlight, ultraviolet light or heat.

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