This section is from the book "Elements Of The Theory And Practice Of Cookery", by Mary E. Williams. Also available from Amazon: Elements Of The Theory And Practice Of Cookery; A Textbook Of Domestic Science For Use In Schools.
A. Let a piece of iron lie wet in the air for several hours. Pour a little water into an old worn tin dish; allow a few drops of water to fall on a steel knife-blade; and let dish and knife lie for some time. What do you observe? Has the tin rusted? How can we keep steel from rusting?
B. Lay one silver spoon next to a rubber band. Wrap another white flannel. Lay a bright brass button in a dry place. Wrap another in damp cloth. Examine all these after a day or two. Would y approve of keeping silver wrapped in white flannel? What effect has dampness on brass?
Rust is a compound, formed in tl presence of moisture, by the union of the oxygen of the a with iron or steel. Rust scales off, and more forms. Thu the metal is eaten away. Rust must be prevented. To do this, keep steel utensils polished, iron ones dry an smooth. Tarnish is a discoloration of polished meta caused by the action of oxygen, sulphur, or some othe element upon the metal. The sulphur used in making rubbe and in bleaching cloth, and the sulphurous gases from burnin coal or gas, form with silver a grayish black compound ii soluble in water.
C. Try to remove the tarnish from silver with whiting, with alcoho from brass with rottenstone, with rottenstone and water, with rottenston and oil, with vinegar or lemon-juice. Compare the effectiveness of tl various materials.
Acids act chemically on tarnisl dissolving it. Oxalic acid, lemon-juice, and vinegar may b used. But, except for spots, it is best to rely mostly upo powders in cleaning metals. A chemical that removes th tarnish may attack the metal. For example, any chemica that brightens zinc, eats into it. If acid is used on any meta all traces of it must be removed by rubbing with powde or the tarnish will quickly reappear. Oil or water, mixe with the powder, forms a paste easy to apply. Use chamois-skin or soft cloth for polishing.