History and Practice of the Art of Photography Part 5

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The evaporation of the water from this bulb decreases the temperature of the mercury in the tube b in proportion to the dryness of the atmosphere, and the number of degrees the tube b indicates below that of the other, shows the real state of the atmosphere in the room; for instance, if b stands at forty and a at sixty-one the room is in a state of extreme dryness, the difference of twenty-one degrees between the thermometers--let a stand at any one point--gives this result. If they do not differ, or there is only four or five degrees variation, the atmosphere of the room is very moist and means should be taken to expel the superfluous quant.i.ty.

HEAD RESTS.--The b.u.t.ton head rest with chair back clip, A fig. 19--is much the best for travelling artists, as it can be taken apart, into several pieces and closely packed; is easily and firmly fixed to the back of a chair by the clamp and screw a and b, and is readily adjusted to the head, as the b.u.t.tons c, c and arms d, d are movable.

Sometimes the b.u.t.ton rest is fixed to a pole, which is screwed to the chair; but this method is not so secure and solid as the clip and occupies more room in packing. Both the pole and clip, are furnished in some cases with bra.s.s band rests instead of the b.u.t.ton; but the only recommendation these can possibly possess in the eyes of any artist, is their cheapness.

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For a Daguerreotypist permanently located the independent iron head-rest, B fig. 19, is the most preferable, princ.i.p.ally on account of its solidity. It is entirely of iron, is supported by a tripod (a) of the same metal and can be elevated by means of a rod (b) pa.s.sing through the body of the tripod, to a height sufficient for a person, standing, to rest against.

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GALVANIC BATTERY.--This article is used for the purpose of giving to imperfectly coated plates a thicker covering of silver. The form of battery now most universally employed for electrotype, and other galvanic purposes, is Smee's--Fig. 20. It consists of a piece of platinized silver, A, on the top of which is fixed a beam of wood, B, to prevent contact with the silver. A binding screw C is soldered on to the silver plate to connect it with any desired object, by means of the copper wire, e. A plate of amalgamated zinc, D, varying with the fancy of the operator from one half to the entire width of the silver is placed on each side of the wood. This is set into a gla.s.s vessel, P,--the extreme ends of the wood resting upon its edge--on which the acid with which it is charged has no effect. The jar is charged with sulphuric acid, (common oil of vitriol) diluted in eight parts its bulk of water. The zinc plates of the battery have been amalgamated with quicksilver, and when the battery is set into the jar of acid there should be no action percieved upon them when the poles F, G, are not in contact. Should any action be percieved, it indicates imperfect amalgamation; this can be easily remedied by pouring a little mercury upon them immediately after removing them from the acid, taking care to get none upon the centre plate A.

Directions for use.--A sheet of silver must be attached to the wire connected with the centre plate A of the battery, and placed in the silver solution--prepared as directed below. The plate to be silvered is first cleaned with diluted sulphuric acid, and then attached to the wire, G, proceeding from the zinc plates D, D, and placed in the silver solution, opposite the silver plate attached to the pole F, and about half an inch from it. A slight effervescence will now be percieved from the battery, and the silver will be deposited upon the Daguerreotype plate, while at the same time a portion of the silver plate is dissolved.

To prepare the solution of silver.--Dissolve one ounce of chloride of silver in a solution of two ounces of cyanide of pota.s.sium, previously dissolved in one quart of water. The oxide of silver may be used instead of the chloride. This solution is put into a tumbler, or other vessel.

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This battery with the necessary articles for using it may be obtained of E. Anthony, 205 Broadway, New York city.

The other articles required by every operator may be simply enumerated, viz:

Sticking, or sealing paper.

A pair of pliers, or forceps.

Porcelain pans or dishes, for applying the hyposulphite of soda and washing after the imagine is fixed, something in form like fig. 23.

A support for holding the plate while being washed, like fig. 24.

[Updater's note: Figures 23 and 24 were missing from the image set.]

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BUFF STICKS.--Fig. 25.--These are usually from one to three feet in length, and about three inches wide--some think two and a half sufficient. The underside, which is convex, is covered with a strip of finely prepared buckskin, or velvet, well padded with cotton or tow.

All the articles enumerated in this chapter may be obtained, of the very best quality and at the most reasonable rates, of Mr. E. Anthony, 205, Broadway, New York.

CHAP. VI.

THE DAGUERREOTYPE PROCESS.

The process of taking Daguerreotype pictures differs very materially from all others of the photographic art, inasmuch as the production of the image is effected upon plates of copper coated with silver. The silver employed should be as pure as possible; the thickness of the plate is of little consequence, provided there be sufficient silver to bear the cleaning and polishing--is free from copper spots, is susceptible of a high polish, an exquisitely sensitive coating and a pleasing tone. These qualities are possessed to an eminent degree by the French plates.

Having already enumerated the various processes--and the apparatus necessary for the manipulation, I will here give a list of the chemicals to be used, and then proceed to explain them more fully. The requisite chemicals are--

NITRIC ACID, ROUGE, DRY IODINE, MERCURY, DRYING POWDER, HYPOSULPHITE OF SODA, CYANIDE OF POTa.s.sIUM, CHLORIDE OF GOLD; OR ROTTENSTONE, HYPOSULPHITE OF GOLD.

TRIPOLI, CHLORIDE OF SILVER.

CHLORIDE OF IODINE, } their compounds, or other BROMINE } accelerating mixtures.

FIRST OPERATION.--Cleaning and polishing the plate.--For this purpose the operator will require the--

Plate Blocks,

Plate Vice

Spirit Lamp,

Polishing Buffs,

Nitric Acid, diluted in fifteen times its bulk of water

Galvanic Battery, to galvanize the plate, if it is too imperfect to be used without, previous cleaning it, as directed in the last chapter.

Rottenstone,

Tripoli, which is too often dispensed with.

Rouge, or lampblack--the first being most preferable. The English operators mix the two together.

Prepared cotton Wool, or Canton flannel. If the first is used, it should be excluded from the dust, as it is not so easily cleansed as the latter.

The plate is secured, with its silver side upward, to the block, by the means described on page 58--having previously turned the edges backward all around. The amount of cleaning a plate requires, depends upon the state it is in. We will suppose one in the worst condition; dirty, scratched, and full of mercury spots, all of which imperfections are more or less to be encountered. The mercury spots are to be removed by burning the plate. To do this hold the plate over the flame of a spirit lamp, more particularly under the mercury spots, until they, a.s.sume a dull appearance, when the lamp is to be removed, and the plate allowed to cool, after which it is attached to the block.

Place the block upon the swivle, and hold it firmly with the left hand; take a small knot or pellet of cotton, or, if you like it better, a small piece of canton flannel--wet it with a little diluted nitric acid; then sift some finely prepared rottenstone--Davie's,* if you can get it--upon it, and rub it over the plate with a continual circular motion, till all traces of the dirt and scratches are removed; then wipe off the rottenstone with a clean piece of cotton, adopting, as before, a slight circular motion, at the same time wiping the edges of the plate. Even the back should not be neglected, but throughly cleansed from any dirt or greasy film it may have received from handling.

* Sold by E. Anthony.

When this is thoroughly accomplished, mix a portion of your tripoli with the dilute nitric acid, to the consistence of thick cream. Then take a pellet of cotton and well polish the plate with this mixture, in the same manner as with the rottenstone. Continue the process till, on removing the tripoli with a clean pellet, the plate exhibits a clear, smooth, bright surface, free from all spots, or scratches. Any remains of the acid on the plate may be entirely removed By sifting on it a little Drying powder, and then wiping it carefully off with a fine camels hair brush, or duster. The finishing polish is now to be given.

For this purpose the rouge--or a mixture of rouge and lamp-black, in the proportion of one part of the former to seven of the latter--is used. It should be kept either in a muslin bag, or wide mouth bottle, over which a piece of muslin is tied--in fact, both the rottenstone and tripoli should be preserved from the dust in the same manner. With a little of this powder spread over the buff--described on page 53--the plate recieves its final polish; the circular motion is changed for a straight one across the plate, which, if intended for a portrait, should be buffed the narrow way; but if, for a landscape or view of a house, the length way of the plate.

The operation of cleaning the plate at first appears difficult and tedious, and many have been deterred from attempting this interesting art on that account; but, in reality, it is more simple in practice than in description, and with a little patience and observation, all difficulties are easily overcome. Great care must be taken to keep the buff free from all extraneous matter, and perfectly dry, and when not in use it should be wrapped up in tissue paper, or placed in a tight box.

The plate should be buffed immediately before the sensitive coating is given; particles of dust are thus effectually removed; the temperature of the plate is also increased by the friction, and the required tint more readily obtained.

SECOND OPERATION.--Applying the sensative coating.--The apparatus and chemicals required, are an

Iodine box--see fig. 14 page 53.