The process of A.C.A. Thiebaut is as follows: the paper has the
following advantages:
First. The sensitive coating is regular, and its thickness is uniform
throughout the entire surface of each sheet.
Second. It can be exposed for a luminous impression in any kind of slide
as usually constructed.
Third. It can be developed and fixed as easily as a negative on glass.
Fourth. The negative obtained dries quite flat on blotting paper.
Fifth. The film which constitutes the negative can be detached or peeled
from its support or backing easily and readily by the hand, without the
assistance of any dissolving or other agent. Thus this invention does
away with all sensitive preparations on glass, which latter is both a
brittle and relatively heavy material, thus diminishing the bulk and
weight of amateur and scientific photographers' luggage when traveling;
it produces photographic negatives as fine and as transparent as those
on glass, in so much that the film does not contain any grain; and,
lastly, it admits of printing from either face of the film, as regards
the production of positives on paper or other material, as well as
plates for phototypy and photo-engraving, which latter processes require
a negative to be reversed.
For the manufacture of my sensitized film paper:
First. A gelatinized sheet of paper is properly damped with cold water,
and when evenly saturated it is placed on a glass, to which it is
attached by means of bands of paper pasted partially on the glass, and
partially on the edges of the said sheet; in this state it is allowed to
dry, whereby it is stretched quite flat.
Secondly. I coat the dry sheet with a solution of ordinary collodion,
containing from one to two per cent. cubic measure of azotic cotton (1½
per cent. gives very good results) and from 1½ to 2½ per cent. of castor
oil (2 per cent. gives very good results); this coating is allowed to
dry; and,
Thirdly. The glass, with the prepared paper upward, is leveled, and then
it is coated, in a room from which all rays but red rays of light are
excluded, with a tepid emulsion of bromide of silver to the extent of
about one millimeter thick, and after leaving it in this position until
the gelatine has set (say) about five minutes, with the film paper still
attached, it is placed upright in a drying-room, where it should remain
about twelve hours exposed to a temperature of from 62 to 66 degrees
Fahrenheit; and,
Fourthly. The film paper is detached from the glass ready for exposure,
development, and fixing in the usual manner. For the purpose of
developing, oxalate of iron or pyrogallic acid answers equally well; for
the purpose of fixing, I have found that a mixture by weight, water,
1,000, hyposulphite of soda 150, and powdered alum 60, produces
excellent results, after being allowed to dry.
Fifthly. The film is peeled off the paper by hand, and can be
immediately used for producing negatives _recto_ or _verso_ as above
mentioned.