290 ENGRAVING 



settled in England, introduced it hero ; he has informed us that a copper-plate 

 thus covered may be made to yield almost any number of impressions, for as the 

 steel coating becomes worn it can be entirely taken off, and a new deposit laid on 

 without injury to the engraving, and this may be done several times. M. Joubert 

 has repeated the experiment with the most satisfactory results. He thus describe* 

 his process in a communication made to the Society of Arts, and printed in their 

 Journal: 



1 If the two wires of a galvanic battery bo plunged separately into a solution of 

 iron, having ammonia for its basis, the wire of tho positive pole is immediately acted 

 upon, while that of the negative pole receives a deposit of the metal of the solution 

 this is the principle of the process which we have named " acierage." 



1 Tho operation takes place in this way : By placing at the positive pole a plate or 

 sheet of iron, and immersing it in a proper iron solution, the metal will bo dissolved 

 under the action of tho battery, and will form an hydrochlorato of iron, which, being 

 combined with the hydrochlorato of ammonia of the solution, will become a bichloride 

 of ammonia and iron ; on a copper-plate being placed at the opposite pole and lik-\\ iso 

 immersed, if tho solution be properly saturated, a deposit of iron, bright and perfectly 

 smooth, is thrown upon the copper-plate, from this principle : 



' Water being composed of hydrogen and oxygen : 



1 Sal-ammoniac being composed of 



1 1st. Hydrochloric acid, containing chlorine and hydrogen ; 



1 2nd. Ammonia, containing hydrogen, nitrogen, and oxygen : 



'The water is decomposed under the galvanic action, and the oxygen fixe.- 

 on the iron plate, forming an oxide of iron ; the hydrochloric acid of the solution 

 acting upon this oxide becomes a hydrochlorate of iron, whilst the hydrogen preci- 

 pitates itself upon the plate of the negative pole, and, unable to combine with it, comes 

 up to the surface of the solution in bubbles. 



'My invention has for its object certain means of preparing printing surface's, 

 whether for intaglio or surface printing, so as to give them the property of yielding a 

 considerably greater number of impressions than they are capable of doing in their 

 ordinary or natural state. And the invention consists in covering the printing surfaces, 

 whether intaglio or relief, and whether of copper or other soft metal, with a very thin 

 and uniform coating of iron, by means of electro-metallurgical processes. And the 

 invention is applicable whether the device to be printed from be produced by engraving 

 by hand, or by machinery, or by chemical means, and whether tho surface printed 

 from be the original, or an electrotype surface produced therefrom. I would remark, 

 that I am aware that it has been before proposed to coat type and stereotypes with a 

 coating of copper, to enable their surfaces to print a larger number of impressions than 

 they otherwise would do ; I therefore lay no claim to the general application of a coat- 

 ing of harder metal on to the surface of a softer one, but my claim to invention is con- 

 fined to the application of a coating of iron by means of electricity on to copper aud 

 other metallic printing surfaces. 



' In carrying out the invention I prefer to use that modification of Grove's battery 

 known as Bunsen's, and I do so because it is desirable to have what is called an in- 

 tensity arrangement. The trough I use for containing the solution of iron in which 

 the engraved printing surface is to be immersed, in order to bo coated, is lined with 

 gutta-percha, and it is 45 inches long, 22 inches wide, and 32 inches deep. In pro- 

 ceeding to prepare for work, the trough, whether of the size above mentioned or 

 otherwise, is filled with water in combination with hydrochlorate of ammonia (sal- 

 ammoniac) in the proportion of 1,000 Ibs. by weight of water to 100 Ibs. of hydro- 

 chlorate of ammonia. A plate of sheet iron, nearly as long and as deep as the trough, 

 is attached to the positive polo of the battery and immersed in the solution. Another 

 plate of sheet iron, about half tho size of the other, is attached to tho negative pole 

 of the battery, and immersed in the solution, and when the solution has arrived at 

 the proper condition, which will require several days, tho plato of iron attached to 

 the negative pole is removed, and tho printing surface to bo coatod is attached to 

 such pole, and then immersed in the bath till the required coating of iron is obtained 

 thereto. If, on immersing the copper-plato in the solution, it be not immediately 

 coated with a bright coating of iron all over, tho bath is not in a proper condition, 

 and the copper-plate is to be removed and tho iron plato attached and returned into 

 tho solution. Tho time occupied in obtaining a proper coatinsr of iron to ;i printing 

 surface varies from a variety of cans-is, Init a workman at'ier some expcricmv and 

 by careful attention will readily know when to rcmov ih< |>l,it<- from the solution ; 

 and it is desirable to state that a copper-plate should not bo allowed to remain in 

 tho bath and attached to tho negative polo of the battery after tho bright, coat i HE of 

 iron begins to show a blackish appearance at the ed^es. Immediately on taking a 

 copper-plato from tho bath great care is to be observed in washing off the solution 



