To cement thin metal sheets, dissolve isinglass cut into little pieces in a small amount of water at a moderate heat, small portions of nitric acid being added, the determination of the proper proportions generally being gained by experiment. Great care should be taken about the amount of nitric acid used. If not enough is taken, the cement will not adhere well; while if too much, the cement will require even weeks for drying.
To cement articles with copper amalgam, first brighten them with acid, then heat to from 176 to 194 degrees Fahrenheit, and after the application of the amalgam, firmly press them together. The adhesion of the parts is as firm as if they were soldered.
Iron cement which will stand red heat is composed of Hessian crucibles 1 part, iron filings 4 parts. Mix these ingredients and wet them with salt water, taking pains not to add too large a quantity of salt, for if this is none the salt would fuse and run from the joints. When this cement is used for joining pipes designed for being laid in the fire, it is placed between the flange of the pipes and pressed together by screws. You can only heat it when it is hard and dry.
An iron cement for high temperatures is composed of:
(1) Iron filings, 20 parts; lime powder, 45; borax, 5; common salt, 5; permanganate of potash. 10. The borax and salts are dissolved in water and are then mixed with the two first-named ingredients as quickly as possible, and used. This cement changes at a white heat to a glassy mass, which is perfectly air-proof.
(2) Permanganate, 25 parts; zinc white, 25; borax, 5. These are treated with a solution of soluble glass, and used at once. This cement must be left to dry slowly, and then it will resist the highest temperature.
A receipt for jewelers' cement, often called Armenian cement, is as follows: Five pieces of gum mastic, about as large as a large pea, are dissolved in a sufficient quantity of spirits of wine to make the mass liquid. Separately, isinglass which has been softened in water (though none of the water must be used) is dissolved in rum, enough being dissolved to make a 2-ounce phial of a very tenacious glue: 2 little pieces of gum ammoniac being added, which must be rubbed or ground until its dissolution. The entire mass then to be mixed to a sufficient heat. This cement is to be kept in a phial closely stoppered, and said phial is to be placed in boiling water when it is to be used. This cement will unite almost all substances, being practically the only cement for glass and polished steel.
(1) For a joint cement, mix equal parts of red lead and white lead, adding enough boiled linseed-oil to give it the right consistency.
(2) Make a soft putty of finely-powdered red lead with ground lead.