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Carbon Printing Without Transfer 664

paper, mixture, water, image, sawdust and print

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CARBON PRINTING WITHOUT TRANSFER 664. The Artigue and Fresson Processes. Used for his own private work from 1878 by F. Artigue, a carbon paper to be used without transfer was placed on the market in 1894 by V. Artigue, under the name of " Charbon Velours." The coating of pigment is obtained by spreading on the paper, which is sized so as to stop-up the pores, a mixture of gelatine, sugar, and glucose. Wilk this is still sticky, it is dusted over with a very finely divided pig ment, according to a method of Beauregard (1857) and of Blair (1863).

Similar results may also be obtained by in corporating the pigment in the mixture of colloids, using about 5 parts of pigment to part of the mixture of gelatine and sugar, and coating paper with an exceedingly thin layer of this mixture ; a similar process is employed in preparing the Fresson paper (Iwo), made in various tints on supports of different textures.

After sensitizing for two to three minutes in a weak solution of bichromate (2 per cent at the most for daylight printing), preferably neutralized by addition of ammonia (till the colour changes from orange to yellow), at a temperature not much above 60 F., the paper is dried in darkness, and printed under the negative in the usual way. There is no need to mask the negative, and printing is timed by means of a photometer.

The exposed print is first soaked for several minutes in cold water, taking care to avoid air bubbles on either side of the paper, and then for a few seconds in tepid water, at a temperature not exceeding 86 F. Here the high-lights of the picture, protected during printing from the action of the light, swell and form an image in relief. During this immersion in the. warm water, especially in the case of Fresson paper, there often appears a silhouette of the image, either negative (in the case of under-exposure) or positive (in the case of over-exposure). In either case the paper should be removed from the warm bath in order to be " developed " before the image becomes distinct.

To do this, the print is fixed by its upper edge to a zinc strip with clips, or laid Oil glass, or other rigid support, held almost vertically, and laved by means of a wide-mouthed coffee pot, or a casserole with a long spout, with a mixture of white wood sawdust 1 (sifted through mesh No. 120) and water, in the pro portion of 2 oz. to 10 oz. of sawdust to 20 OZ. (if water warmed to about 68'15' F. 2 in a large tub, above which the print is held. The mixture of sawdust and water must be poured on to the upper margin of the print, so as not to attack too vigorously the image over which it flows.

The slight friction of the sawdust on the previously swollen image drags away the pig ment more quickly from the parts which are in greater relief and thus impedes the streaming, these differential frictions giving the modelling of the half-tones.

The same sawdust mixture may be used repeatedly, especially with addition of an anti septic. Also, from time to time, it can be filtered on fine linen and washed with very hot water to free it from soluble matter.

The operator may use local control, by lighten ing certain parts with a stronger jet of the saw dust mixture squirted directly on, or by gentle touches with a brush or wet tuft of cotton-wool.

The image is somewhat tender, and should not be submitted to prolonged washing, so that it is best to eliminate the bichroinate by immersion in a very dilute solution of sodium bisulphite, after which the print is briefly rinsed, and left to dry of itself by hanging it on a line.

665. Papers Exposed through the Back. At tempts have been made at various intervals to revive the use, in pictorial photography, of ordinary carbon tissues, rendered semi-trans parent with paraffin oil after sensitizing, and then exposed through the support (V. Blanch ard, 1895) ; or the exposure could be through a translucent paper (e.g. Japanese paper) on to which the carbon tissue had been transferred on removal from the sensitizing bath.

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