The principle of this stain is simply the hydrogen gas contained in the coal acting on the iron, iron being of a softer nature than the steel, which it does not affect, the flame also possessing a quantity of tar, it is imperceptibly embodied by the iron during the action of the oxide, and, when finished, by filling up the spaces created, it becomes decidedly more impervious to damp or wet than any other stain or browning which is composed entirely of oxide of iron.
CHAPTER XXXI.
RECIPES FOR BROWNING GUN BARRELS.
Solution for Browning Gun Barrels.—Make a solution by putting together in a glass vessel, spirits of nitre, three-quarter ounce; tincture of steel, three-quarter ounce; black brimstone, one-quarter ounce; blue vitriol, one-half ounce; corrosive sublimate, one-quarter ounce; nitric acid, one drachm, and copperas, one-quarter ounce. Mix with one and one-half pints of rain water, and bottle for use. Clean the barrel till entirely bright, rubbing it over with finest emery paper, then apply the solution with a clean white cloth. Set away for twenty-four hours. At the end of this time a rust will have formed over the barrel. Go over it with a steel scratch-brush, then rub off all the rust with a woolen cloth. If you find the brown not dark enough, cover again with the solution and set away twenty-four hours longer. Remove the rust exactly as in the first instance, then, the color suiting, wash off with a wet cloth, rub to thorough dryness, and finish by rubbing with linseed oil, to prevent further rusting.
This application browns the barrel beautifully, and in case of twist leaves the markings prominently plain.
The tincture of steel is sometimes not to be obtained at a small drug store, in which case the unmedicated tincture of iron may be made to answer reasonably well.
2. Sulphate of copper, one ounce; sweet spirits of nitre, one ounce; water, one pint. Mix. In a few days it will be ready for use.
3. Tincture muriate of iron, one ounce; nitric ether, one ounce; sulphate of copper, four scruples; rain water, one pint; if the process is to be hurried, add two or three grains of oxymuriate of mercury. Put in lime water to neutralize acid.
4. Spirits of nitre, one pound; alcohol, one pound; corrosive sublimate, one ounce. Mix and cork for use.
5. Tincture of muriate of iron, one ounce; nitric ether, one ounce; sulphate of copper, four scruples; rain water, one pint.