Scientific American Supplement, No. 315, January 14, 1882 eBook

This eBook from the Gutenberg Project consists of approximately 112 pages of information about Scientific American Supplement, No. 315, January 14, 1882.
Pyrogallic acid......................... 10 parts. 
Citric acid............................. 45 "
Water...................................410 "

The developer—­which, it will be noted, is very acid—­is warmed before it is used, say to a temperature of 30 deg. to 40 deg.  C.; nevertheless, the development does not proceed very quickly.  As we watched, exactly eight minutes elapsed before Mr. Winter cried out sharply, “That will do.”  Immediately one of the assistants seizes the wet canvas, crumples it up without more ado, as if it were dirty linen, and takes it off to a wooden washing trough, where it is kneaded and washed in true washerwoman fashion.  Water in plenty is sluiced over it, and after more vigorous manipulation still, it is passed from trough to trough until deemed sufficiently free from soluble salts to tone.  The toning—­done in the ordinary way with gold—­removes any unpleasant redness the picture possesses, and then follows the fixing operation in hyposulphite.  As canvas is more permeable than paper, these two last processes are quickly got through.

The final washing of the canvas is very thorough.  Again it is treated with all the vigor with which a good laundry-maid attacks dirty linen, the canvas, in the end, being consigned to a regular washing-machine, in which it is systematically worked for some time.

When the canvas picture at last is finished, it presents a very rough appearance, by reason of the tiny fibers that stand erect all over the surface.  To lay these, and also to improve the surface generally, the canvas is waxed, the fabric is stretched, and a semi-fluid mass rubbed into it, heat being used in the process, which not only gives brilliancy, but seems also to impart transparency to the shadows of the picture.  The result is a pleasant finish, without vulgar glare or glaze, the high lights remaining beautifully pure and white.

Of course, the price of these canvas enlargements varies with the amount of artistic work subsequently put upon them; but the usual charge made by Messrs. Winter for a well-finished life-size portrait, three quarter length, is sixty florins, or about L5 sterling as the exchange now stands.  Besides working for photographers, Messrs. Winter are reproducing a large number of classic paintings and cartoons by photography on canvas in this way (some of them almost absolutely untouched), and these, as may be supposed, are finding a very large sale among dealers.  Such copies must necessarily be of considerable value to artists and collectors, and altogether it would seem that Messrs. Winter have hit upon a novel undertaking, which bids fair to make them a handsome return for the outlay (large as it undoubtedly has been) made upon their Vienna establishment.—­Photo.  News.

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DETECTION OF STARCH SUGAR SIRUP MIXED WITH SUGAR-HOUSE MOLASSES.[1]

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Scientific American Supplement, No. 315, January 14, 1882 from Project Gutenberg. Public domain.
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