thin the engraving will always press through. Before cementing it on the inside of the lid, in order not to injure the polish, it is coated with chalk dissolved in alcohol, which is first allowed to dry. Next melt the shellac on the stick, heat the watch lid and put it on. After the engraving has been done, simply force the lid off and remove the remaining shellac from the latter by light tapping. If this does not remove it completely lay the lid in alcohol, leaving it therein until all the shellac has dissolved. All that remains to be done now is to wash out the watch lid.
Jewelers’ Glue Cement.
—Dissolve on a water bath 50 parts of fish glue in a little 95-per-cent alcohol, adding 4 parts, by weight, of gum ammoniac. On the other hand, dissolve 2 parts, by weight, of mastic in 10 parts, by weight, of alcohol. Mix these two solutions and preserve in a well-corked flask. For use it suffices to soften it on the water bath.
Casein Cements.—
| I.— | Borax | 5 parts |
|---|---|---|
| Water | 95 parts | |
| Casein, sufficient quantity. | ||
Dissolve the borax in water and incorporate enough casein to produce a mass of the proper consistency.
II.—The casein is made feebly alkaline by means of soda or potash lye and {21} then subjected for about 24 hours to a temperature of 140° F. Next follow the customary admixture, such as lime and water glass, and finally, to accomplish a quicker resinification, substances containing tannin are added. For tannic admixtures to the partially disintegrated casein, slight quantities—about 1 per cent—of gallic acid, cutch, or quercitannic acid are employed. The feebly alkaline casein cement containing tannic acid is used in the well-known manner for the gluing together of wood.
For Metals.
—Make a paste with 16 ounces casein, 20 ounces slaked lime, and 20 ounces of sand, in water.
For Glass.
—I.—Dissolve casein in a concentrated solution of borax.
II.—Make a paste of casein and water glass.
Pasteboard And Paper Cement.
—I.—Let pure glue swell in cold water; pour and press off the excess; put on the water bath and melt. Paper or other material cemented with this is then immediately, before the cement dries, submitted to the action of formaldehyde and dried. The cement resists the action of water, even hot.
II.—Melt together equal parts of good pitch and gutta percha. To 9 parts of this mass add 3 parts of boiled linseed oil and 1/5 part litharge. The heat is kept up until, with constant stirring, an intimate union of all the ingredients has taken place. The mixture is diluted with a little benzine or oil of turpentine and applied while still warm. The cement is waterproof.
III.—The National Druggist says that experience with pasting or cementing parchment paper seems to show that about the best agent is casein cement, made by dissolving casein in a saturated aqueous solution of borax.
IV.—The following is recommended for paper boxes:
| Chloral hydrate | 5 parts |
| Gelatin, white | 8 parts |
| Gum arabic | 2 parts |
| Boiling water | 30 parts |
Mix the chloral, gelatin, and gum arabic in a porcelain container, pour the boiling water over the mixture and let stand for 1 day, giving it a vigorous stirring several times during the day. In cold weather this is apt to get hard and stiff, but this may be obviated by standing the container in warm water for a few minutes. This paste adheres to any surface whatever.
Waterproof Cements For Glass, Stoneware, And Metal.
—I.—Make a paste of sulphur, sal ammoniac, iron filings, and boiled oil.
II.—Mix together dry: Whiting, 6 pounds; plaster of Paris, 3 pounds; sand, 3 pounds; litharge, 3 pounds; rosin, 1 pound. Make to a paste with copal varnish.
III.—Make a paste of boiled oil, 6 pounds; copal, 6 pounds; litharge, 2 pounds; white lead, 1 pound.
IV.—Make a paste with boiled oil, 3 pounds; brickdust 2 pounds; dry slaked lime, 1 pound.
V.—Dissolve 93 ounces of alum and 93 ounces of sugar of lead in water to concentration. Dissolve separately 152 ounces of gum arabic in 25 gallons of water, and then stir in 62 1/2 pounds of flour. Then heat to a uniform paste with the metallic salts, but take care not to boil the mass.
VI.—For Iron and Marble to Stand in Heat.—In 3 pounds of water dissolve first, 1 pound water glass and then 1 pound of borax. With the solution make 2 pounds of clay and 1 pound of barytes, first mixed dry, to a paste.
VII.—Glue to Resist Boiling Water.—Dissolve separately in water 55 pounds of glue and a mixture of 40 pounds of bichromate and 5 pounds of alum. Mix as wanted.
VIII. (Chinese Glue).—Dissolve shellac in 10 times its weight of ammonia.
IX.—Make a paste of 40 ounces of dry slaked lime 10 ounces of alum, and 50 ounces of white of egg.
| X.— | Alcohol | 1,000 parts |
|---|---|---|
| Sandarac | 60 parts | |
| Mastic | 60 parts | |
| Turpentine oil | 60 parts |
Dissolve the gums in the alcohol and add the oil and stir in. Now prepare a solution of equal parts of glue and isinglass, by soaking 125 parts of each in cold water until it becomes saturated, pouring and pressing off the residue, and melting on the water bath. This should produce a volume of glue nearly equal to that of the solution of gums. The latter should, in the meantime, have been cautiously raised to the boiling point on the water bath, and then mixed with the hot glue solution.
It is said that articles united with this substance will stand the strain of cold water for an unlimited time, and it takes hot water even a long time to affect it. {22}
| XI.— | Burgundy pitch | 6 parts |
|---|---|---|
| Gutta percha | 1 part | |
| Pumice stone, in fine powder | 3 parts |
Melt the gutta percha very carefully add the pumice stone, and lastly the pitch, and stir until homogeneous.
Use while still hot. This cement will withstand water and dilute mineral acids.
Leather And Rubber Cements.
I.—Use a melted mixture of gutta percha and genuine asphalt, applied hot. The hard-rubber goods must be kept pressed together until the cement has cooled.
II.—A cement which is effective for cementing rubber to iron and which is especially valuable for fastening rubber bands to bandsaw wheels is made as follows: Powdered shellac, 1 part; strong water of ammonia, 10 parts. Put the shellac in the ammonia water and set it away in a tightly closed jar for 3 or 4 weeks. By that time the mixture will
