S60 



ANNUAL REGISTER, 1805. 



J. L. Romd. Frmn the Biblio- 

 theque Fhysico - Economique. 



For this purpose it is necessary 

 to have a small conical cask of deal, 

 one metre in height, and fifty or 

 sixty centimetres in diameter, pro- 

 \ided with wooden hoops. Adjust 

 to it a lid, closing hermetically, and 

 a double moveable bottom, on 

 which place the engravings, which 

 are separated, and supported by 

 very fine glass tubes, rounded with 

 care at the lamp. To mix tlie water 

 properly with the muriatic acid, 

 pour them both, by means of a fun- 

 nel, into a large leaden pipe, which 

 passes llirough the cover, and rests 

 on the double bottom. Before the 

 engravings are placed in the ap- 

 paratus destined for cleaning them, 

 they are divided into two parts ; the 

 first comprises those that are greasy, 

 such as are glued on canvass, or 

 pasted on paper: the second, those 

 that are only stained and sj)otted 

 with ink. Having placed all those 

 of the first class in an caithen ves- 

 sel, or a small cask of deal, fill it 

 with a warm and very weak solu- 

 tion of potash, or a solution which 

 may be procured by the lixiviation 

 of ashes. Two or three hours are 

 sufficient to take out all the spots : 

 the liquor is th,en emptied out, and 

 replaced Avith clear water, in order 

 to remove all the alkaline parts 

 which would contribute to weaken 

 the oxygenated muriatic a-cld. The 

 ■water being drawn off, and theen- 

 gra\ings having become dry, place 

 them in the blvachiug-vessel, con- 

 centrically, either lengthwise or 

 breadthwise, according to their di- 

 Kiensio'.s, in the spaces left between 

 thsj tubes, and so as aot to be too 

 much crowded, first introducing the 

 laj^est, and reserving the middle for 



the smallest. By these means they 

 may be the more easily extended, 

 and in taking them out they are not 

 liable to be torn. Having put on 

 the cover, pour at the same time the 

 water aud the oxygenated muriatic 

 acid into the leaden tube, which 

 must then be taken out, that the 

 apparatus may be exactly closed, 

 l^et the engravings be in whatever 

 state they may, they are commonly 

 clean in two or three hours, which 

 may be ascertained by examining 

 one of those placed in the centre. 

 That the operator may not be in- 

 commoded by tlie smell, when the 

 bleaching is finished, he must tura 

 the cock, which, by means of a pipe, 

 conducts the liquor into a large 

 covered vessel, placed under the ap- 

 paratus ; but as the gas and the 

 acid with which the engravings are 

 still impregnated might render the 

 labour inconvenient, and even dan- 

 gerous, it must be again filled with 

 pure water. ]f the |)rints are on 

 strong paper, they may be taken 

 one by one out of the water ; but if 

 they are thin and much worn', it is 

 better (o draw off the liquid, and to 

 let then harden. They are then 

 laid to drain on hurdles, covered 

 with linen cloths : after wliich thcy 

 are washed on both sides with plenty 

 of water, either on inclined marble 

 slabs, or on frames ol white cloth. 

 This operation is very essential, for 

 the engravings sometimes turn yel- 

 low again rcry soon, when they 

 have not' been sufficiently washed. 

 They are then spread on hurdles, 

 provided with napkins, or on paste- 

 board covered with white paper ; 

 and that they may not dry too 

 quickly, they should neither be ex- 

 posed to the sun nor to a strong 

 currant of air. While yet a little 

 damp thpy uic laid between two 



she«t« 



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