(m) Removing Paint Stains.—3 parts potash, 1 oz. caustic lime; lay on with a padded stick and let remain some hours.
(n) Ditto.—Moisten with washing soda dissolved in warm water; renew for ½ hour; wash off with clean water.
(o) Bottles.—If oily or otherwise greasy, they should not be washed with water, but wiped with dry tow, or a dry dirty cloth, so as to remove as much grease as possible. By changing the cloth for one that is clean, the vessel can be wiped until all traces of grease disappear.
(p) Ditto.—A strong solution of an alkali, such as pearlash, may be used, whereby the removal of the grease is materially facilitated.
(q) Ditto.—If soiled by resin, turpentine, resinous varnishes, &c., wash with a strong alkaline solution, and rub by means of the wire and tow.
(r) Ditto.—If the alkali fail to act, a little sulphuric acid may be employed with advantage. The latter acid will also be found advantageous in removing pitch and tar from glass vessels. Nitric or sulphuric acid may be employed to clean flasks which have contained oil.
(s) Ditto.—“To clean a silver-bottle, pour in a strong solution of potassium cyanide; shake a few times, pour out, and rinse with water 2 or 3 times, and your bottle is perfectly clean. Keep the solution, and filter and strengthen when required. By doing this you can sun your bath better in 2 hours than in a week’s exposure in the dirty black bottles photographers appear to delight in.” (Phil. Phot.)
(t) Ditto.—Alexander Müller, of Berlin, after speaking of the various methods in vogue for cleaning glass vessels, as, for example, sand (which is objectionable, as it scratches glass), shot (good, but should be followed by a wash of dilute nitric acid, to get rid of lead), brushes, copper scale (also good, but requires subsequent rinsing with some dilute acid), bits of paper or linen, wood ashes, salt (especially rock-salt), gypsum and marble-dust (very good), ground bones (likewise excellent), he concludes as follows:—Chisel or tongue-shaped pieces are cut from thick pieces of indiarubber, and a sharp brass or platinum wire is fixed into the thick end to serve as a handle. With this washer and its flexible handle, we are able to “lick” out, to a certain extent, any kind of a bottle. For beakers and capsules, we greatly prefer it to the hair pencil and feather commonly used; for, owing to their fibrous structure, the precipitate gets entangled in them, while they also lose some of their nitrogenous particles, which would affect the accuracy of careful nitrogen determinations, as, for example, in water analyses. Finally, to clean glass or porcelain vessels from the greatest variety of adherent organic substances, he recommends a mixture of bichromate of potassium and sulphuric acid as superior to ether, alcohol, benzine, &c.
(u) Bottles which have contained petroleum, wash with thin milk of lime, which forms an emulsion with the petroleum, and removes every trace of it; by washing a second time with milk of lime and a small quantity of lime chloride, even the smell may be so completely removed as to render the vessel, thus cleansed, fit for keeping beer in. If the milk of lime be used warm, instead of cold, the operation is rendered much shorter. (Ding. Pol. Jl.)
(v) Decanters.—There is often much difficulty experienced in cleaning decanters, especially after port wine has stood in them for some time. The best way is to wash them out with a little pearlash and warm water, adding a spoonful or two of fresh slaked lime if necessary. To facilitate the action of the fluid against the sides of the glass, a few small cinders may be used.