ETHENE 307 



ETCHING ON GLASS. See GLASS, and ENGRAVING ON GLASS. 



ETCHING VARNISH. (Aetzgrund-Dcckfirniss, Ger.) Though tho practice 

 of the elegant art of etching does not come -within the scope of our Dictionary, the prepa- 

 ration of the varnishes, and of the biting menstrua which it employs, legitimately 

 belongs to it. 



Tho varnish of Mr. Lawrence, an English artist resident in Paris, is made as 

 follows : Take of virgin wax and asphaltum, each two ounces, of black pitch and 

 burgundy-pitch, each half an ounce. Melt the wax and pitch in a new earthenware 

 glazed pot, and add to them, by degrees, the asphaltum, finely powdered. Let the 

 whole boil till such time as that, taking a drop upon a plate, it will break when it is 

 cold, on bending it double two or three times betwixt tho fingers. The varnish, 

 being then enough boiled, must be taken off the fire, and after it cools a little, must 

 be poured into warm water, that it may work the more easily with the hnncft, so 

 as to be formed into balls, which must be kneaded, and put into a piece of taffety for 

 use. 



Care must be taken, first, that the fire be not too violent, for fear of burning the in- 

 gredients, a slight simmering being sufficient ; secondly, that whilst the asphaltum is 

 being put in, and even after it is mixed with the ingredients, they should be stirred 

 continually with the spatula ; and, thirdly, that the water into which this composition is 

 thrown should be nearly of the same degree of warmth with it, in order to prevent a 

 kind of cracking that happens when the water is too cold. 



Preparation of the hard varnish iised by Callot, commonly called the Florence Var- 

 nish. Take four ounces of fat oil very clear, and made of good linseed oil, like that 

 used by painters ; heat it in a clean pot of glazed earthenware, and afterwards put 

 to it four ounces of mastic well powdered, and stir the mixture briskly till the whole 

 be well melted, then pass the mass through a piece of fine linen into a glass bottle with 

 a long neck, that can be stopped very securely ; and keep it for the use that will be 

 explained below. 



Method of applying the soft varnish to the plate, and of blackening it. The plate 

 being well polished and burnished, as also cleansed from all greasiness by chalk or 

 Spanish white, fix a hand-vice on the edge of the plate where no mark is intended to 

 be, to serve as a handle for managing it when warm ; then put it upon a chafing-dish, 

 in which there is a moderate fire, and cover the whole plate equally with a thin coat 

 of the varnish ; and whilst the plate is warm, and the varnish upon it in a fluid state, 

 beat every part of the varnish gently with a small ball or dauber made of cotton 

 tied up in taffety, which operation smooths and distributes the varnish equally over 

 the plate. 



When the plate is thus uniformly and thinly covered with the varnish, it must be 

 blackened by a piece of flambeau, or of a large candle which affords a copious smoke ; 

 sometimes two or even four such candles are used together for the sake of despatch, 

 that the varnish may not grow cold, which if it. does during the operation, the plate 

 must be heated again, that it may be in a melted state when that operation is performed ; 

 but great care must be taken not to burn it, which, when it happens, may be easily 

 perceived by the varnish appearing burnt and losing its gloss. 



The menstruum used and recommended by Turrell, an eminent London artist, for 

 etching upon steel, was prepared as follows : 



Take Pyroligneous acid 4 parts by measure, 

 Alcohol 1 part, mix, and add 



Nitric acid 1 part. 



This mixed liquor is to be applied from 1 to 15 minutes, according to the depth 

 desired. The nitric acid was employed of the strength of 1-28 the double aqua-fortis 

 of the shops. 



The eau forte or menstruum for copper, used by Callot, as also by Piranesi, with a 

 slight modification, is prepared with 8 parts of strong French vinegar, 



4 parts of verdigris, 

 4 sea salt, 

 4 sal-ammoniac, 

 1 ., alum, 

 16 water. 



The solid substances are to be well ground, dissolved in the vinegar, and diluted 

 with the water ; the mixture is now to be boiled for a moment, and then set aside to 

 cool. This method is applied to the washed, dried, and Tarnished plate, after it has 

 suffered the ordinary action of aqua-fortis, in order to deepen and finish the delicate 

 touches. It is at present called the eau forte a passer. 

 See OLEFIANT GAS. 



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