Apply the following solution by means of a brush, after having removed any grease by rubbing with a clean, dry cloth: 100 parts of stannic chloride are dissolved in 1,000 parts of water; this solution is added to one containing 2 parts tartaric acid dissolved in 1,000 parts of water, and finally 20 cubic centimeters indigo solution, diluted with 2,000 parts of water, are added. After allowing the solution to act upon the stain for a few seconds, it is rubbed clean, first with a moist cloth, then with a dry cloth; to restore the polish use is made of silver sand and jewelers' rouge.


When the rust is recent it is removed by rubbing the metal with a cork charged with oil. In this manner a perfect polish is obtained. To take off old rust, mix equal parts of fine tripoli and flowers of sulphur, mingling this mixture with olive oil, so as to form a paste. Rub the iron with this preparation by means of a skin.


The rusty piece is connected with a piece of zinc and placed in water

containing a little sulphuric acid. After the articles have been in the liquid for several days or a week, the rust will have completely disappeared. The length of time will depend upon the depth to which the rust has penetrated. A little sulphuric acid may be added from time to time, but the chief point is that the zinc always has good electric contact with the iron. To insure this an iron wire may be firmly wound around the iron object and connected with the zinc. The iron is not attacked in the least, as long as the zinc is kept in good electric contact with it. When the articles are taken from the liquid they assume a dark gray or black color and are then washed and oiled.


The rust on iron and steel objects, especially large pieces, is readily removed by rubbing the pieces with oil of tartar, or with very fine emery and a little oil, or by putting powdered alum in strong vinegar and rubbing with this alumed vinegar.


Take cyanide of calcium, 25 parts; white soap, powdered, 25 parts; Spanish white, 50 parts; and water, 200 parts. Triturate all well and rub the piece with this paste. The effect will be quicker if before using this paste the rusty object has been soaked for 5 to 10 minutes in a solution of cyanide of potassium in the ratio of 1 part of cyanide to 2 parts of water.


To remove rust from polished steel cyanide of potassium is excellent. If possible, soak the instrument to be cleaned in a solution of cyanide of potassium in the proportion of 1 ounce of cyanide to 4 ounces of water. Allow this to act till all loose rust is removed, and then polish with cyanide soap. The latter is made as follows: Potassium cyanide, precipitated chalk, white castile soap. Make a saturated solution of the cyanide and add chalk sufficient to make a creamy paste. Add the soap cut in fine shavings and thoroughly incorporate in a mortar. When the mixture is stiff cease to add the soap. It should be remembered that potassium cyanide is a virulent poison.


Apply turpentine or kerosene oil, and after letting it stand over night, clean with finest emery cloth.


To free articles of iron and steel from rust and imbedded grains of sand the articles are treated with fluorhydric acid (about 2 per cent) 1 to 2 hours, whereby the impurities but not the metal are dissolved. This is followed by a washing with lime milk, to neutralize any fluorhydric acid remaining.