None of the compounds of lead stain the skin, an advantage which has led to a preference being given to them by many persons who are clumsy manipulators, and to the more extensive use of them than of other hair dyes.
The salts of silver above referred to are more rapid in their action as hair dyes than those containing lead. It is only necessary to wash the hair quite clean and free from grease, then to moisten it with a weak solution of one of them, and, lastly, to expose it to the light, to effect the object in view. Sunlight will fully darken it in a few minutes, but in diffused daylight it will take two or three hours, or longer, to acquire the deepest shade. To avoid this delay and inconvenience, the common practice is, a few minutes after applying the silver solution, to moisten or wet the hair with a solution of sulphuret of potassium, or of hydrosulphuret of ammonia. The effect is immediate, and the full depth of shade which a silver solution of the strength employed is capable of imparting is at once produced. A few minutes later and the hair and skin may be rinsed with tepid water, gently wiped dry, and the hair finally adjusted with the comb. The effect of its application, its rapid action, and the satisfactory nature of the effect produced, all tend to render a solution of nitrate of silver the favorite hair dye of those who have sufficient skill and steadiness of hand to use it properly.
It will be useful here to inform the inexperienced reader that all solutions and compounds which contain nitrate of silver stain the skin as well as the hair, if they be allowed to touch it. These stains may be removed, when quite recent, by rubbing them with a piece of rag or sponge wetted with a weak solution of potassium, of hydrosulphuret of ammonia, or of iodide of potassium; but as this is attended with some trouble and inconvenience, the best way is to avoid the necessity of having recourse to it. The hairdressers commonly adopt the plan of smearing hard pomatum or cosmetique over the skin immediately surrounding the hair to be operated upon, in order to protect it from the dye. By very skillful manipulation, and the observance of due precautions, the hair may be thoroughly moistened with the silver solution without touching the adjacent skin; but this can only be done when the hair of the head is under treatment by a second party.