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Varnish

varnishes, resins, oil, gums, spirit, water, soluble, sandarac and turpentine

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VARNISH. A solution of gums or resins which is applied to the surface of objects to afford a glaze and protect the article so coated. Its use is largely decorative and applied to en hance the appearance of woodwork (furniture and house fittings) as it brings out the beauties of the grain and color of woods more dis tinctly and permanently and at less cost than the process of polishing, being applied with a brush similarly to painting. Varnish is also used. as an upper or outside coating of paint to enhance and make more permanent the pigments. The ancient Egyptians were ac quainted with the art of varnishing, but its origin appears to have arisen in the East. In India, China and Japan the practice of lacquer work, a species of varnish application, was known at a very early date. It has been claimed that Japan was acquainted with the art of lacquering 500 or 600 B.c., but the majority of authorities place its first usage there to the 3d century of our era, as an art acquired from their neighbors the Coreans. The natives of China and India probably knew the art much earlier than the Japanese. Varnish and lacquer work are, however, generally treated in the arts as separate and distinct. True var nish does not appear to have been known in Europe till the 17th century.

A practical varnish will cover the following requirements : It must be a homogeneous fluid or solution ; must be fixed or permanent in effect as to tone of color, transparency (or opaque ness), and must, on application in thin layers by brush or otherwise, dry within a short period by evaporation of its volatile solvents (alcohol, ether, benzene, spirits of turpentine, etc.), leaving a film of smooth, lustrous (some times purposely dull), elastic oil and resin, im pervious to its surrounding atmospheric con ditions. It must when dry be free from cracks or flaws. In general varnishes may be divided into natural, oil, spirit and water varnishes. Natural varnishes so called are the group of lacquers as used in India, China and Japan and are produced in liquid form by nature as the saps or juices of trees (Rhus vernicifera). They are generally treated under the title lac quers (to which refer) and will not be con sidered here. Oil varnishes: These are a prod uct manufactured from linseed oil, gum resins, driers, and a solvent such as turpentine or white spirit. The gums are largely fossil resins. Oil varnishes in commerce are frequently divided into the two general classes: carriage varnishes and cabinet varnishes; both are of very similar character as to composition and manu facture, but the best and most durable for open air use are selected as carriage varnishes, the re mainder being termed and used as cabinet var nishes. Spirit varnishes consist of a kind made from various resins dissolved in a volatile spirit —methylated spirit (grain alcohol dena turized), turpentine, etc. They are generally

made without oil, but some have a small ad mixture of oil. Water varnishes find but small application in the industrial arts. There are lac water varnish, glazing varnish, glue varnish and crystal water varnish. The first makes a good paper varnish and is used on harness, as is also the glue varnish.

y Materials used in the manufacture of var nishes may be placed under the following groups : drying oilsesins, gums, solvents and G coloring matter. Good drying oils are made from old linseed oil of the best quality (best Baltic preferred). It should be aged at least a year before use•by being stored in containers to exclude any attack of the air. While difference between raw and old stored oils is great, the cause is' not known to science, nor have the chemists discovered the reactions caused in ageing. The selection of resins in the ingredients employed is more important than any other, for the lustre and permanence of the products depends absolutely on the qualities of the resins used. Gums as known in commerce are the exudations from trees and consist of what are termed water soluble and spirit soluble. The water soluble gums are of course not correctly used in varnishes as it is required that varnishes shall not be affected by water. For varnishes the resins available for the commercial markets are: amber, kauri, copal, dammar, shellac, mastic, sandarac, ben zoin, elemi, animi, pine resin (rosin), asphal tum. Most resins come to the market either in the form of knotty masses, drops, cylindrical pieces or blocks. In the factory the gums are divided into classes as follows: oil varnish gums, as amber, animal, copals, sandarac, rosin and kauri. Ethereal varnish resins are : all oil resins after they have been fused; dammars, mastic, sandarac, rosin, Manila copal. Spirit varnish gums are: lac, Manila copal, sandarac, mastic, rosin, melted resins. The points or characteristics to be considered are hardness, fusibility, solubility, appearance, color. The resins mentioned under oil varnish are insoluble in oils, ether and other solvents, until liquified by fusion; rosins, some soft copals ana san darac are exceptions being soluble in alcohol. The gums grouped under ethereal varnish are more or less soluble in benzol, coal-tar naphtha,, turpentine, ether, acetone, etc. The enumerated spirit varnish gums are soluble in alcohol and methylated spirit. Natural coloring matters used in varnishes are: turmeric, gamboge, dragon's blood, gum accroides, aloes, etc. Some artificial or coal-tar colors also enter into the manufacture of varnishes.

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