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Towler, John. The Silver Sunbeam.
Joseph H. Ladd, New York: 1864. Electronic edition prepared from
facsimile edition of Morgan and Morgan, Inc., Hastings-on-Hudson,
New York. Second printing, Feb. 1974. ISBN 871000-005-9
Chapter II.
PRELIMINARY OBSERVATIONS.
THE art of Photography comprehends all the operations of taking a
picture on a sensitive surface by means of light and chemical
reagents. These operations are as varied as the different substances
on which they are taken, or by which they are taken. In all cases,
whatever may be the process, the conditions required in the
operation of producing a photographic image are, firstly, a suitable
groundwork or receptacle, such as paper, metal, glass, or stone;
secondly, a coating of substances called sensitizers, which are very
sensitively affected by light and altered according to its
intensity; thirdly, chemical ingredients, denominated developers,
that act differently upon the parts that have been changed by light
from what it does upon the parts upon which light has not acted at
all or feebly; fourthly, fixing agents or chemical solvents of the
sensitizing agents that have not been changed by light. Other
important conditions are comprehended in the light, requiring it to
be of a certain intensity, in a certain direction, and in a certain
quantity.
The various sorts of matter for the reception of the photographic
image have given rise to a variety of processes, whose appellations
refer rather to the material employed than to any difference in the
actinic principle; thus, on paper, exist a number of so-called
processes, as, for instance, printing by direct contact, and
printing by development; the plain-paper process, the wax-paper
process, the resin process, and the albumen process. On glass are
found the negative process, the positive or ambrotype process, and
the transfer process. On metal the melainotype and daguerreotype
processes and photo-engraving; and on stone, photolithography. In
addition to these may be mentioned the card-picture process and that
of the stereograph. In reference to the materials used in the
sensitized photographic film, or rather to contain the sensitizing
ingredients, stand out most prominently; the Collodion processes,
wet and dry, the Tannin process, and the Albumen process.
The sensitizing substances most generally used are the salts of
silver in combination with organic matter. In the carbon process, as
also in photo-lithography, photoengraving, photo-zincography, and
photo-glyphography, the sensitive materials are gelatinous or
resinous substances in combination with certain chemical reagents
that render them insoluble, and in which the solubility, in certain
menstrua, is again restored by the agency of light. The salts that
have hitherto been used are the bichromate of potassa and the
sesqui-salts of iron; the receptacles, asphaltum and gelatine; and
the solvents, hot water, oil of turpentine, and oil of lavender. The
fixing agents or solvents of the undecomposed iodides, bromides, and
chlorides of silver in the collodion, albumen, or surface-sensitized
film, on which the rays of light have not acted, or but partially
acted, are hyposulphite of soda, cyanide of potassium and
sulphocyanide of ammonium. The chemical reagents that either develop
the latent image or perfect that which light has already commenced,
are the proto-salts of iron, ammonia, gallic and pyrogallic acid,
formic acid, and, in the daguerreotype-plate, mercury. Other
materials are used in addition to intensity the image already formed
by the ordinary developers. The principle involved in the
strengthening of negatives is, first, probably by certain electrical
decompositions, to produce a deposit oil the shadows formed by means
of silver, mercury, lead, or iodine; and secondly, to blacken this
deposit by sulphurizing or reducing agents, or by the alkalies.
The great divisions into which photographic operations may be
divided are those which treat of negatives and positives. A
negative is an actinic impression on glass or waxed paper, in which
the lights and shadows are inverted, as also the figures and the
different items that form the picture; that is, right becomes left,
and left right. The negative is the matrix from which photographic
prints are obtained either on paper or other material; these prints
are produced either by direct contact of the paper or glass with the
negative, or the negative is placed in one focus of a camera, and
the paper or glass in its conjugate focus. Such prints or
impressions, whether by reflected or transmitted rays, are
positives, in which the lights and shades, as well as all the
delineations, are in their true and natural position. There is
another class of positives in which the shading is natural, but the
delineations are inverted; these are exemplified in the
Daguerreotype, ambrotype, and melainotype, which are exhibited only
by reflected light.
As the present work is intended for practical men, it will be
necessary at the very outset to give a list of all the articles and
arrangements required in the successful pursuit of the photographic
art.
LIST OF A PHOTOGRAPHIC OUTFIT.
- Glass-house, or room in the garret furnished with a sky-light.
- Dark room, for sensitizing plates or papers.
- Operating room, for collodionizing plates, mounting prints, etc.
- Screens (white, gray, blue, and artistic) for the glasshouse.
- Lenses, (¼, 1/3, 4/4, etc., stereoscopic and orthoscopic.)
- Cameras, (for portraits, views, stereographs and for copying.)
- Ornamental carpets, chairs, stands, curtains, pillars,
balustrades, etc.
- Head-rests, etc., camera-stands, mirrors, brushes, combs, pins,
needle, and thread.
- Washhand-stand. pitcher and basin, soap and towels,
clothes-brush and nail-brush.
- Stove, tongs, shovel, poker, coal or wood-box.
- Antechamber, suitably furnished with lounges, etc.
- Show-cases for artistic productions, and cases for chemicals,
etc.
- Collodion, (negative and positive,) acetic acid, nitric acid,
citric acid, tartaric acid, protosulphate of iron, gallic acid,
pyrogallic acid, formic acid, carbonate of soda, carbonate of lime,
(chalk,) chlorinetted lime, nitrate of silver, citrate of soda,
phosphate of soda, blue litmus-paper, red litmus-paper, sulphide of
potassium, sulphocyanide of ammonium, ammonia, oxide of silver,
iodide of potassium, iodide of ammonium, iodide of cadmium, iodine,
tincture of iodine, bromide of potassium, bromide of ammonium,
bromide of cadmium, bromine, nitrate of uranium, bichloride of
mercury, gum-arabic, starch, gelatine, glue, shellac, chloride of
gold, acetate of soda, alcohol, ether, distilled water, loaf-sugar,
cyanide of potassium, hyposulphite of soda, pyroxyline, sulphuric,
acid, rotten-stone, tannin, sesquichloride of iron, oxalic acid,
varnish, hydrochloric acid, acetate of lead, caustic potassa, salts
of tartar, chloride of Sodium, chloride of ammonium, bichromate of
potassa, asphaltum, copal, chloroform, cotton, nitroglucose, mastic,
resin, thus, benzoin, benzine, wax.
- Funnels, filtering-stands, collodion-glasses, developing and
fixing-glasses, porcelain or photographic-ware baths and dishes,
filtering-paper, plain paper, plain-salted paper, albumen paper,
arrowroot paper, tinted paper, resinized paper, wax paper, blotting
paper, plate-cleaners, plate-holders, Canton flannel, cotton cloths,
silk cloths, brushes, colors, pencils, scale and compasses,
magnifying-glass, cases, mats, preservers, glass plates of various
sizes, (transparent and ground,) melainotype-plates, black leather,
black velvet, black varnish, black paper, scissors, pliers, pens,
ink, paper, post-stamps, envelopes, pocket-knife, black
lead-pencils, gutta-percha dishes, pails, towels, pitcher,
ice-cooler, soft water, focussing-cloths, brooms, hand-brush,
diamond, cutting board for glass, shelves for negatives, drawers for
mounts, papers, etc., beaker-glasses, wash-tubs, scales, weights and
graduated measures, dropping-tubes, test-tubes and rack,
evaporating-dishes, crucibles and furnace, tongs, coal or wood,
door-mats, hat-stand, artificial paraphernalia, as stuffed birds,
beasts, etc., skeletons, vases, printing-boxes, fuming boxes, forms
for cutting out stereographs, card-pictures, etc., card-board,
mounts of various sizes, spatula, pestle and mortar, India-rubber,
lamps, candles, frames for photographs, solar camera and its
appendages, solar microscope and accessories, glue-pot, tea-kettle,
changing-box for dry plates.
- For out-door work will be required extra: a small hand-cart and
tent, or dry collodion or tannin-plates, wax-paper, graduated tape,
saw, hatchet, hammer and nails, negative-holder.
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