The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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The first formula gives an emulsion suitable for preparing paper
to be used for printing from dense negatives, the second from
medium negatives, and the third from thin negatives. Of the
third Mr. Burton says: " There is just about enough of ammonium
chloride and of sodium citrate formed by the double decomposition
of the citric acid, and of part of the soda, to decompose the whole
of the nitrate of silver. The formula works all right, and the paper
that results from the use of it keeps very fairly. The paper
resulting from either of the other formulae will probably keep as
long as any sensitised paper. The following is the method of
emulsifying. The two solutions are heated to a temperature of
noo to I20o F. The temperature should not be greater than 1200,
or there is a great chance that some of the insoluble silver salts
produced will be thrown down in the granular form. A is then
added slowly to B with much stirring. The emulsion is filtered
through a double thickness of cambric, and is then immediately
ready for use. If it is wished to keep the emulsion for any
length of time, 10 per cent, of alcohol, in each ounce of which a
few grains of thymol have been dissolved, should be added to the
emulsion. It is to be observed, however, that, even with this
addition, emulsion by formula No. 3 will not keep for very long."
Mr. Burton recommends floating the paper for three or four
minutes to coat it, or by brushing the emulsion over the paper,
allowing it to get surface dry and repeating the operation. The
temperature of coating room should be Joo F. The above quantity
of emulsion will coat eight sheets 22 by 17, or ten or twelve
by floating. Either gold or platinum may be used for toning, but
the prints should be well washed first. The best method of
coating the paper is a question of quantity : in small quantity the
paper should be wetted thoroughly in warm water, and squeegeed
to a sheet of glass, and the emulsion poured on it; with larger
quantities the sheets should be drawn over the surface of the
fluid emulsion. The majority of operators will no doubt prefer
to buy their paper ready made, and the following may be
considered as the necessary manipulations for producing perfect
prints, although this paper undoubtedly gives its best results
when used for rather thin negatives or those wanting in contrasts.
The paper, cut to the required size, is placed in contact with the
film side of the negative in the ordinary printing frame, and
placed in a good printing light. Where the negative is exception-