Grafist@aol.com
Date: 03/12/03-03:24:25 PM Z
Matti, Chris and all,
Following is a quote from Wall's ''The Dictionary of Photography'', 12th
ed., p 368; The Photo-Miniature, Oct. 1910.
''The sensitizer is a saturated solution of potassium bichromate, the gum is
dissolved in the proportion of 2 of gum to 3 of water, with 2 or 3 drops of
formaline in each ounce (30ml) of the thick solution to preserve it. Powder
or tube colors are used, and the secret of making the coating mixture is to
use just enough of the gum solution to hold the pigment together, and no
more. The bichromate solution is added after the gum and pigment have been
well ground together in a mortar, in the proportion of four to six times the
quantity of gum and pigment mixture.
The gum-bichromate mixture is applied by brushes in the usual way to a
non-stretching stout paper, which Mr.Zimmerman advocates, or paper can be
coated with the air brush. The development of the gum print is by what is
termed the ''blotting-paper'' method. The prints, of which a great number
can be treated at once, if necessary, are sandwiched between sheets of wet
blotting-paper. When a pile of wet blotters and wet prints is ready, it is
placed on a piece of glass, and another piece on top and the pile, with glass
top and bottom, is then placed under water. If the exposures have been
correct, the blotters may be removed in about an hour or so, when the prints
will be perfectly developed, and a perfect negative image of each picture
will be absorbed on to the blotting-paper. Moreover, the surface of the print
will be in just the right condition for local work. ''
Hope this can be of use.
John - Photographist- London
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