48 ANNUAL OF SCIENTIFIC DISCOVERY. 



washed with clear water, and afterwards dried with a bellows or 

 other means ; then such parts of the etching as are of sufficient depth 

 should be covered with the varnish, in the same manner as the blem- 

 ishes to which we have referred. This operation may be performed 

 any number of times, each time washing and drying the plate ; this 

 must be also done when the biting is completed ; and then, by 

 gently heating the back of the plate, the wall may be drawn off, 

 and by means of a little spirit of turpentine and oil the surface of 

 the plate may be cleared of the etching-ground. There are other 

 operations, such as re-biting, re-etching (by touching with the 

 graver), and by working with a point without the use of acid, etc., 

 etc. ; these, however, would require much space to describe, and this 

 we will not just now do, as it is more particularly our object in men- 

 tioning the above to make operations which might be useful in many 

 manufactures more readily understood. 



In the same manner, but with the use of different acids, and on 

 any scale, etching may be applied to steel, iron, brass, glass, and, 

 lately, we are told, to porcelain. For steel, nitric acid very largely 

 diluted with pyroligneous acid until it does not taste much stronger 

 than vinegar, is best. On brass, we have seen diaper, and other 

 ornaments, produced with great clearness and rapidity in the follow- 

 ing manner. On large works, such as monumental brasses, experi- 

 ence has shown that in the biting, either by nitric or nitrous acid, 

 before a great depth is got the biting of the lines is stopped by the 

 formation of a black oxide, which it requires a very strong prepara- 

 tion of nitric and sulphuric acid to remove and keep in solution ; 

 and this after a time proves too strong, and tears up the ordinary 

 etching-ground ; it has, however, been found that turpentine-varnish, 

 if allowed for a few days to harden, has a great resistance ; and by 

 the use of this, when diapers, etc., are outlined, the raised parts may 

 be painted with the varnish, and, when hard, the acid applied ; and 

 it is astonishing what good effect may be produced by these means. 

 Large surfaces for the relief of foliage, figures, letters, etc., may, by 

 this means, be executed with rapidity, either for filling in with col- 

 ored shellac or pigments. 



The painting of these ornamental plates with varnish might be 

 the means of affording employment to females, and probably the 

 preparation of embossing, and otherwise ornamenting glass to be 

 bitten by fluoric acid, might also be brought into far more extensive 

 use than it is at present, and would also provide a certain amount 

 of respectable labor for females. 



A NEW SYSTEM OF ENGRAVING. 



A new method of engraving has recently been patented in Eng- 

 land by George Wallis, of London. Pulverized materials, sufficiently 

 hard to be pressed into the metallic plate to be engraved, are mixed 

 to a suitable paste, the picture is formed with this paste upon paper, 

 vegetable parchment, or other fibrous material, which is then laid 

 upon the metal plate and passed with it between two rollers, subject- 

 ing it to a pressure sufficiently powerful to sink the hard material of 

 the paste into the metal, thus forming the engraving. 



