Manufacturer and builder 10 / 1869
The following process for bleaching the ivory plates of piano-forte keys is recommended by Professor Artus. Lay the ivory plates in a flat vessel containnig a solution of carbonate of soda. For each pound of ivory take two thirds of a pound of crystals of carbonate of soda, and two pounds of soft water. This solution is left in contact with the ivory for two days and two nights and is then poured off, after which the ivory is well rinsed with pure water. The dissolve three quarters of a pound of sulphite of soda in two pounds of soft water, and immerse the ivory in the solution. After it has lain for from five to six hours, add gradually one ounce of muriatic acidmixed wuth four ounces of water, and keep stirring the liquid during the addition; cover the vessel well, and let it again remain for thirty-six hours, after which the liquid may be poured off. The plates must then be rinsed with water, and dried in the air. If not sufficiently bleached, repeat the operation a second or even a hird time. In adding the muriatic acid, care must be taken not to inhale the sulphurous gas which is liberated from the sulphite of soda.