1818.] and on the Composition of the Ink. 371 



refuses to absorb any more. A wooden roller covered with 

 leather, and charged with very fine engravers' ink, is then passed 

 two or three times over the surface of the stone, and adheres to 

 all the lines made with the prepared ink, and to those only. A 

 sheet of paper, not so damp as is required in copper-plate print- 

 ing, is next laid carefully on, a board is placed above it, and 

 then, by turning the winch, the roller, exerting a pressure of more 

 than 10001b., passes slowly over the surface of the board, and 

 the process is finished by removing the board and taking out the 

 print thus produced. It is necessary to take about a dozen 

 proofs before the work comes to its full perfection. After a 

 number of impressions have been taken, the more delicate parts 

 will begin to be a little blurred. As soon as this is perceived, 

 remove the stone from the press, and first pass over it a sponge 

 filled with rectified oil of turpentine, and then wash it well with 

 pure water. By this treatment the whole design will be appa- 

 rently discharged : this, however, is not the case ; for on passing 

 the roller charged with ink over the surface of the stone, every 

 line, even the most delicate, which was in the original drawing, 

 will again become visible, and the printing may be proceeded 

 with as at first. 



Article XIIJ. 



Further Observations on the French Varnish, or Polish for 

 Cabinet Work, &;c. By Thomas Gill, Esq. 



(To the Editors of the Annals of Philosophy.) 



No. 11, Cuvent Garden Chambers, 

 GENTLEMEN, April U. 1818. 



Having, since my former communication on this subject, on 

 January 14, inserted in your Annals for February, obtained 

 additional information on the process by which larger surfaces 

 may be varnished at once, with as much facility as the smaller 

 ones before recommended, and consequently much time, labour, 

 and expense be saved, 1 should deem myself unpardonable in 

 withholding it from the public. 



The improvement consists in the use of a rubber formed of a 

 flat coil of thick woollen cloth, such as drugget, which must be 

 torn off the piece, in order that the face of the rubber, which is 

 made of that edge of the cloth, may be soft and pliant, and not 

 hard and stiff, as would be the case were it to be cut off, and 

 thereby be liable to scratch the softened surface of the varnish. 

 This is to be securely bound with thread to prevent it from un- 

 coiling when it is used ; and it may vary in its size from one to 

 three inches m diameter, and from cine or" two inches in thickness, 



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