CEMENT. 155 



The last varnish is prepared by boiling iib of asphalt "with 

 lOft) of the drying oil used in the first step of the process, 

 and then stirring in Sib copal varnish and lOlfe terpentine. 

 It must have a month's age before it is fit for use. — Patent 

 Journal. 



Elastic Varnish. — 2 pts. rosin, or dammar-resin, and 1 pt. 

 caoutchouc are fused together, and stirred until cold. To add 

 to the elasticity, linseed oil is added. Another varnish for 

 leather is made by putting pieces of caoutchouc in naphtha 

 until softened into a jelly, adding it to an equal weight of heated 

 linseed oil, and stirred for some time together, while over the 

 fire. 



Cement for Luting Joints of Steam Apparatus. — Serbat 

 prepared a mastic instead of the red-lead cement used for 

 this purpose, by thoroughly incorporating sulphate of lead, 

 black oxide of manganese, and linseed oil. See Lond. Journ. 

 1849, 61. 



For the preparation of a lubricating grease from rosin oil, 

 see the Report on Serbat's process, in Lond. Journ, 1849, 58. 

 The quantity made by Serbat in 1847 was 305,000}]b, which 

 may give some idea of its value. 



Cement {glue). — Herberger recommends the following as 

 an excellent cement to join metal with glass or porcelain. To 

 2 oz. glue, dissolved in water and boiled down to a thick solu- 

 tion, are added 1 oz. oil varnish, or | oz. Venice terpentine, 

 and the whole heated to ebullition to incorporate them tho- 

 roughly. The articles cemented should remain 48-60 hours 

 before use. 



A good cement for glass, porcelain, and pottery, which is 

 not to be exposed to water, is to mix equal parts dry quick- 

 lime and gum arable, in fine powder, and to moisten the whole 

 with water or white of egg, to make a thick paste. {Eisner.) 

 Quicklime and white of egg alone make an excellent cement 

 of this kind ; but the diamond cement, a dilute alcoholic solu- 

 tion of fish glue and resin, is far superior, although more 

 Gostly, and will withstand a considerable exposure to moisture. 



Emery and sand-paper, being made with glue, which is liable 



