It is in general more economical to buy varnishes than to make them on the small scale. Occasionally, however, our readers may find themselves in a situation where a simple recipe for a good varnish will prove valuable. We give a few recipes which are easily followed, and which will undoubtedly prove useful in special cases.
The following varnish for basket work is said to dry rapidly, to possess sufficient elasticity, and to be applicable with or without admixture of color: Heat 375 grains of good linseed oil on a sand bath until it becomes stringy, and a drop placed on a cold, inclined surface does not run; then add gradually 7,500 grains of copal oil varnish, or any other copal varnish. As considerable effervescence takes place, a large vessel is necessary. The desired consistency is given to it, when cold, by addition of oil of turpentine.
The external surfaces of brass and iron are generally blacked or bronzed with compositions given under the head of lacquers. The insides of the tubes of telescopes and microscopes should be coated with a dead black varnish so as to absorb the light and prevent any glare. The varnish that is generally used for this purpose consists of lampblack, made liquid by means of a very thin solution of shellac in alcohol, but such varnish, even when laid on warm metal, is very apt to scale off and thus produce two serious evils - the exposure of the bright metallic surface and the deposit of specks on the lenses. It will therefore be found that lampblack, carefully ground in turpentine, to which about a fifth of its volume of gold size or boiled linseed oil has been added, will adhere much more firmly. The metal should be warm when the varnish is applied. Care must be taken not to use too much gold size, otherwise the effect will be a bright black instead of a dead black.
1. For those objects to which it is applicable one of the best black varnishes is obtained by applying boiled linseed oil to the iron, the latter being heated to a temperature that will just char or blacken the oil. The oil seems to enter into the pores of the iron, and after such an application the metal resists rust and corrosive agents very perfectly.
2. Fuse 40 oz. of asphaltum and add 1/2 a gallon of boiled linseed oil, 6 oz. red lead, 6 oz. litharge, and 4 oz. sulphate of zinc, dried and powdered. Boil for two hours and mix in 8 oz. fused dark amber gum and a pint of hot linseed oil, and boil again for two hours more. When the mass has thickened withdraw the heat and thin down with a gallon of turpentine.
There is a most beautiful transparent green varnish employed to give a fine glittering color to gilt or other decorated works. As the preparation of this varnish is very little known, an account of it may in all probability prove of interest to many of our readers. The process is as follows: Grind a small quantity of a peculiar pigment called "Chinese blue," along with about double the quantity of finely-powdered chromate of potash, and a sufficient quantity of copal varnish thinned with turpentine. The mixture re-jmires the most elaborate grinding or incorporating of its ingredients, otherwise it will not be transparent, and therefore useless for the purpose for which it is intended. The "tone" of the color may be varied by an alteration in the proportion of the ingredients. A preponderance of chromate of potash causes a yellowish shade in the green, as might have been expected, and vice versa with the blue under the same circumstances. This colored varnish will produce a very striking effect in japanned goods, paper hangings, etc., and can be made at a very cheap rate.