86 



CEMENTS. 



Ji Cement for Glass Grinders. — Take 

 pitch and boil it; add thereto, and keep 

 stirring it all the whilp, fine sifted wood 

 ashes, until you have it of a proper tem- 

 per; a little tallow may be added, as you 

 find it necessary. For small work, to 

 four ounces of rosin add one-fourth of an 

 ounce of beeswax, melted together, and 

 four ounces of whitening, made previous- 

 ly red hot. The whitening should be put 

 in while hot, that it may not have time to 

 imbibe moisture from the atmosphere. 



Shellac is a very strong cement for 

 holding metals, glass, or precious stones, 

 while cutting, turning, or grinding them. 

 The metal, &c., should be warmed to 

 melt it. For fastening rub}' cylinders in 

 watches, and similar delicate purposes, 

 shellac is excellent. 



To Solder or Cement broken glass. — 

 Broken glass may be soldered or cement- 

 ed in such a manner as to be as strong as 

 ever, by interposing between the parts 

 glass ground up like a pigment, but of ea- 

 sier fusion than the pieces to be joined, 

 and then exposing them to such a heat as 

 will fuse the cementing ingredient, and 

 make the pieces agglutenatc without being 

 themselves fused. A glass for the pur- 

 pose of cementing broken pieces of flint 

 glass may be made by fusing some of the 

 same kind of glass, previously reduced to 

 powder, along with a little red lead and 

 borax, or with the borax only. 



Cement Jar Zhrbi/shire Spar and 

 other Stones. — A cement for this purpose 

 may be made with about seven or eight 

 parts of rosin, and one of beeswax, melted 

 together, with a small quantity of plaster 

 of Paris. If it is wished to make the ce- 

 ment fill up the place of any small chips 

 that may have been lost, the quantity of 

 plaster must be increased a little. When 

 the ingredients are well mixed, and the 

 whole is nearly cold, the mass should be 

 well kneaded together. The pieces of spar 

 that are to be joined, must be heated until 

 they will melt the cement, and then press- 

 ed together, some of the cement being pre- 

 viously interposed. Melted sulphur ap- 

 plied to fragments of stones, previously 

 heated by placing them before a fire, to at 

 least the melting point of sulphur, and 

 then joined with the sulphur between, 

 makes a pretty firm and durable joining. 

 Little deficiencies in the stone, as chips out 



of corners, &c., may also be filled up with 

 melted sulphur, in which some of the pow- 

 der of the stone has been melted. 



Jl Cement that will stand against 

 boiling water and. the pressure of steam. 

 — In joining the flanches of iron cylinders 

 and other parts of hydraulic steam engines, 

 great inconvenience is often experienced 

 from the want of a durable cement. Boil- 

 eil linseed oil, litharge, and red and white 

 lead, mixed together to a proper consist- 

 ence, and applied on each side of a piece 

 of flannel, previously shaped to fit the 

 joint, and then interposed between the 

 pieces before they are brought home, as 

 the workmen term it, to their place, by 

 the screws or fastenings employed, make 

 a close and durable joint. 



The quantities of the ingredients may 

 be varied without inconvenience, only 

 taking care not to make the mass too thin 

 with oil. It is difficult, in many cases, 

 instantly to make a good fitting of the 

 large pieces of iron work, which renders 

 it necessary sometimes to join and sepa- 

 rate the pieces repeatedly, before a proper 

 adjustment is obtained. When this is 

 expected, the white lead ought to predo- 

 minate in the mixture, as it dries much 

 slower than the red. A workman know- 

 ing this fact, can he at little loss in exer- 

 cising his own discretion in regulating the 

 quantities. It is safest to err on the side 

 of the white lead, as the durability of the 

 cement is no way injured by it, only a 

 longer time is required for it to dry and 

 harden. When the fittings will not ad- 

 mit easily of so thick a substance as flan- 

 nel being interposed, linen may be substi- 

 tuted, or even paper or thin pasteboard. 



This cement answers well also for join- 

 ing broken stones, however large. Cis- 

 terns built of square stones, put together 

 with this cement, will never leak, or want 

 any repairs. In this case the stones need 

 not be entirely bedded in it; an inch, or 

 even less, of the edges that lie next the 

 water, need only be so treated; the rest of 

 the joint may be filled with good lime. 



Another Cement that will stand the 

 action of boiling water or steam. — This 

 cement, which is preferable even to the 

 former for steam engines, is prepared as 

 follows: Take two ounces of sal ammoni- 

 ac, one ounce of flowers of sulphur, and 

 sixteen ounces of cast iron filings, or bor- 



