The very cheap varnishes are made from common rosin treated in various ways, with the idea of hardening the rosin and rendering it, if possible, less liable to the action of dampness or moisture which causes rosin to fluoresce or turn white. The extreme brittleness of rosin and its likelihood to soften at a lower temperature than most other gums, compels special hardening treatment to be resorted to. Some very fair interior varnishes are now produced from rosin by processes too lengthy to describe here. There are a multitude of brands of varnishes adapted to various and special requirements in the arts. We shall only consider the ones of immediate interest to the painter.

The brands, names and kinds of varnishes for carriage and exterior and interior house work are legion, yet they admit of simple classification and in many cases, differ only in name and price. In the first class are varnishes containing from 20 to 30 gallons of linseed oil to the 100 pounds of gum. This includes the wearing bodies and all carriage and other exterior finishing varnishes; the so-called spars, marine and the better grades of inside finishing. They are made from Zanzibar, kauri, or a mixture of the two in varying proportions. In a general way, therefore, any good grade exterior finishing is adaptable to practically all the uses for which the hundreds of outside finishings under many and divers names are recommended.

Interior finishes are usually made from lower grades of kauri, manila, and some rosin, with somewhat less oil. You, therefore, never go wrong in doing inside finishing on woodwork with a spar or exterior varnish, unless rubbed work is required. Hard oil finishes, interior coach, number one furniture, number one coach, and similar varnishes are made from low priced gum and rosin, with from 6 to 10 gallons of oil to the 100 pounds of gum, and the thinner used is apt to be in part, at least, if not wholly, benzine, for the price at which these varnishes are sold does not admit of anything else. These cheaper grades of varnish yellow with age, because of the benzine they contain, and turn white and perish easily, because of the small amount of oil and the nature of the gum used.

Under short oil varnishes are classed all rubbing varnishes, whether for carriage, furniture, or house use. The best grades contain gums similar to those used in the exterior finishes and from 6 to 10 gallons of oil to the 100 pounds of gum. The cheaper grades of rubbing contain cheaper gums, and some rosin. Floor varnish is a compromise between a short oil, hard drying varnish, and a varnish of the so-called long oil variety. It must have hardness and elasticity combined.

Cheap hard oils, furnitures, copals, ceiling, and sizing varnishes are made mostly from rosin or very low grade manila and rosin mixtures, thinned with cheap solvents. Some of these cheap varnishes are very good for the purposes intended, as the art of producing good cheap varnishes has been made a special study. The trouble is that the purchaser usually expects too much from cheap varnishes and is, therefor, disappointed.

What does it cost to make an ordinary gum var-nnish?

The yield would be from 35 to 38 gallons and the cost of the raw materials entering into each gallon of varnish approximately, $1.40 per gallon, to which must be added the cost of manufacture and the dozen and one other items of expense which the manufacturer must bear. Manilla varnishes can be made somewhat cheaper. The bare cost of material in the making of a cheap pure gum varnish can hardly be brought under one dollar per gallon.

The linseed oil used in oil varnishes is boiled with the addition of certain so-called dryers, of which red lead and certain compounds of manganese treated in various ways are the most important. The drier is introduced into the oil, either direct or through the medium of the resinates or oleates of lead and manganese.

Liquid dryers are made by heating together some compound of lead or manganese with linseed oil or rosin and thinning the mixture after proper treatment with turpentine or benzine, to what is considered proper strength to be put on the market. They owe their drying power to the fact that salts of lead and manganese have the property of combining with oils and resins to form oleates and resinates of these metals, lead and manganese. These oleates and resinates are soluble in oil, turpentine and benzine and impart the drying properties to the oil in the paint into which they are introduced. They hasten the oxidation or drying of linseed oil by acting as carriers of oxygen from the air to the oil.

Linseed oil gains from 14 to 16 per cent. in weight in drying, due to the oxygen it absorbs.

Japan dryer and other heavy bodied siccatives are made in the same general way as liquid dryers and owe their body to the addition of gum resin or shellac and the use of less reducer.

In the fabrication of oil varnish, the gum resin to be used is carefully sorted and a definite amount, usually 100 to 150 pounds, styled a "batch," placed in a large kettle, preferably of copper. The capacity of such a kettle is usually from 75 to 125 gallons. The kettle of gum is placed over a hot fire of coke and the gum carefully melted, either with or without covering the top of the kettle. When no cover is used, it is styled an open melt; when the gum has properly melted, prepared linseed oil is added and the mixture further heated and stirred and dryer added if necessary. The kettle is then drawn from the fire, allowed to cool sufficiently and then turpentine or benzine is added in sufficient quantity to give a proper varnish body to the mixture when cool. The varnish is then carefully filtered and tanked for sometime, as ageing materially improves oil varnishes.

Cheap varnishes are simply filtered and are then ready for the market.

Many special processes have been introduced, and particular methods of procedure, but in a general way, the foregoing gives the processes in common use.

To test the quality of liquid and Japan dryers it is only necessary to add the dryer to pure, raw linseed oil in the proportion of one part of dryer to ten parts of oil. Mix thoroughly, and spread in a thin film on glass and allow the film to dry, observing the length of time required to cause the oil to become tacky, dust free and dry.

A good dryer should dry twenty parts of oil in 12 to 24 hours at the longest. Other features of the dryer can be observed also. The dryer should mix readily with the oil, otherwise if it separates and is insoluble, it can be put aside as of little value. The behavior in drying should also be noted. The film of oil should dry smooth and free from crinkles and striae or other imperfections. Comparisons between different dryers can be made easily by this method of adding fixed, accurately measured proportions of dryer to raw oil and observing the action of the mixtures side by side. A fluid ounce of liquid contains 480 drops. 24 drops of dryer to the ounce of raw linseed oil would be about 1 part to 20.

Varnishes can be tested by spreading them on glass and observing their action in drying and the nature of the surfaces they produce. Exposure to steam and the weather will develop their wearing qualities or lack of them.