Page:Popular Science Monthly Volume 92.djvu/418

 Varnish and Varnishing

Strange gums and oils and how they are made into protective coatings

By H. M. Beattie

��VARNISHES are of two kinds. Spirit varnishes are made by dissolving a gum, such as shellac, in alcohol, but oil varnishes, in which class are most of the varnishes we know com- mercially, are made by cooking resinous gums in oil, and adding thinners, such as turpentine, or a petroleum product.

The charac- ter of the var- nish depends on the quali- ties and prop- erties of the raw materials used. Much gum and little oil produce the hard, high gloss, rubbing-var- nishes used on pianos and fur- niture. Var- nishes which must be more elastic and tougher, but which are not exposed to the weather, con- tain a less pro- portion of gum to oil, while the exterior varnishes of all kinds contain the greatest quantity of oil and are known as "long- oil" varnishes. Varnish which is used on a railway coach must have elastic qualities, and must be able to withstand the ele- ments better than the varnish used on a chair, or on the interior trim of a house. The varnish that is used on tables and interior trim must be able to withstand mor(! blows and rough treatment than the carriage varnish. The varnish maker has spent many years in developing a

���The long-leaf pine which grows in our Southern States produces both turpentine and resin

��particular varnish for each particular pur- pose, and while he makes a universal varnish adaptable to almost any need, experience has shown that for the best work, a particular varnish manufactured for a particular purpose always gives more lasting satisfaction.

Varnish Mak- ing Begins in New Zealand

The gums used in var- nish come mostly from New Zealand and from Af- rica. The gum from New Zea- land is called kauri gum and is the best known. It is a semi-fossil resin that has been buried in the ground, many hun- dreds of years. It is sought for in primitive ways. Armed with a long iron rod, the native prospec- tor explores the ground sometimes to a depth of six feet. He can tell by touch when he strikes gum. He then digs up the piece, which may weigh a few ounces or many pounds. He sorts this gum and sells it to the for- eign middleman who in turn deals with the varnish maker. The kauri gum is a harder, tougher gum than the African gum and commands a higher price.

The oil most used in the manufacture of varnish is linseed oil. Linseed oil is obtained from flaxseed. Flaxseed has

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