Varnishes are more or less transparent liquids which are used to provide a protective surface coating in much the same way as paints do” At the same time they allow the original surface to show but add a lustrous and glossy finish to it. All varnishes have basically the same components as paints.
Varnish is a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials. Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent. Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss sheens by the addition of "flatting" agents.
Types of varnishes
Natural resin varnishes:
Body made from natural resin obtained from certain trees. Natural resin obtained from living trees or from fossils(which are superior) Vehicle in varnish is the same as used in oil-based paint. Resins dissolved in oil ► mixture heated to temperature (500-600OF) depending on the amount of gloss required. Oil and natural resin varnish ► OLEO RESINOUS varnish. Thinner and dryers used in varnish are the same as used in oil based paints
Modified natural-resin varnishes:
Made from natural resin ► altered by chemical action. Common resin is heat treated with glycerin to form a gum. This gum is treated as the body for the varnish. Less expensive varnish than the oleo resinous varnish
Synthetic resin varnish:
Synthetic varnish produced by plastic industry
Chemicals used include nitrocellulose, amino resins, silicon etc
Vehicle most often the same as for oleo resinous varnish
Coal tar derivatives may be used as thinners
Dryer is also the same as for other types of varnishes
CLASSIFICATION OF VARNISHES
Long oil varnish:
Long oil contain 40 to 100 gal of oil per 100 lbs of resin
Takes longer time to dry
Marine and spar varnish belongs to this group
Tung oil used ► impervious to water
Medium oil varnish:
Medium-oil contain 12 to 40 gal of oil per 100 lbs of resin
They dry faster ► harder
Harder film than long-oil varnish but are not impervious to water
Floor varnish belongs to this group
- Short oil resins:
Short-oil contain 5 to 12 gal of oil per 100 lbs of resin. Dry rapidly ► form a hard, brittle film that withstand much rough usage. Polishing varnish belongs to this group
How to Varnish
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They are paints used for the treatment of masonry walls. Water instead of oil is used as a vehicle ► known as water-paint too. Powdered white chalk and glue boiled in water are mixed. Usually colored by mixing different pigments. All Distempers mixed with water only before being used. Distemper affected by weathering condition and takes off if washed ► to be used only in interior works. Cheap, durable and easy interior finish. Should be applied on clean and dry surface.