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 become a perfectly liquid transparent mass and is then ready for use. When applied to rubber the ammonia softens it, but it quickly evaporates, leaving the rubber in the same condition as before. The shellac clings to the iron and thus forms a firm bond between the iron and the rubber.
| III.— | Gutta percha white | 1 drachm |
|---|---|---|
| Carbon disulphide | 1 ounce | |
| Dissolve, filter, and add: | ||
| India rubber | 15 grains | |
| Dissolve. | ||