Recreative Science: A Record and Remembrance of Intellectual Observation, Vol. II. Groombridge and Sons, Paternoster Row, London, 1861 p.43
FIG. 1. Kinnear's Camera, and Stand.
FOR those who wish to practise landscape photography, or to take photographs of any objects at a distance from the operating room, what is termed a "dry process" is indispensable. Great ingenuity has been brought to bear in the invention of photographic tents, portable operating-rooms, dark boxes, vans, and even photographic cabs and wheel-barrows; these have for their object to render the collodion. process, in its simplicity, capable of being used in the field, and certainly the idea of pitching one's tent in a shady nook near a stream, in the midst of beautiful scenery, taking negatives, and knowing that they are good before one leaves the spot, is rather captivating; but, unfortunately, there is much to dispel the illusion. The great weight and bulk of the tent and bath, bottles and chemicals, plate-box and plates, besides the camera and stand, and the host of difficulties and annoyances which are inseparable from tent life, are such that few amateurs care to go out with a tent second time. With a "dry process," a person may go from home for several weeks with no other photographic encumbrance but his portable camera and stand (Fig. 1), and a parcel of sensitive plates, take the views he wishes, and return home to develop them at his leisure. It is sometimes stated that a "dry process" can never produce pictures equal to a "wet one;" that the negatives are hard, and wanting in atmospheric effect. In answer to this, a prize medal was recently offered by the Photographic Society of Scotland for the best landscape by any process, open to all the world; the medal was awarded to a landscape taken by the collodio-albumen process, which is the one now to be described.
Many processes have been invented for the preparation of sensitive dry plates, and every month sees the publication of one or two new ones; but none of them appear to equal this in the certainty and the beauty of the negatives. The apparatus required, in addition to that for the wet collodion process, are--
A glass bath and dipper for aceto-nitrate solution.
A levelling stand (Fig. 2).
Fig. 2.-- Levelling Stand with Glass Plate on it.
Two four-ounce beaker glasses and small funnel (Fig. 3).
The chemicals required are--
Solution of aceto-nitrate of silver to fill bath.
Prepared collodion for "dry process."
Pyrogallic developing solution.
Silver developing solution.
As stated in the former paper, the best plan for an amateur, who has not much time at his command, is to get most of his solutions as nearly ready for use as possible, and to procure them from a person who understands the process, and therefore knows exactly what is requisite. The formulae are, however, here given for the solutions, for those who prefer to prepare their own:
|White of egg||1 oz.|
|Liquor ammoniac||10 minims.|
|Iodide of potassium||5 grains.|
|Bromide of potassium||1 grain.|
|Tincture of iodine||1 minim.|
Beat up well together; allow to stand and filter. It will keep good many months.
|Distilled water||1 oz.|
|Nitrate of silver||40 grains.|
|Glacial acetic acid||25 minims.|
|Pyrogallic acid||2 grains.|
|Nitrate of silver||10 grains.|
|Hyposulphite of soda||5 oz..|
FIG. 3,-Beaker Glasses for Albumen.
Pour collodion on the plate, and immerse it in the nitrate of silver bath, as in the ordinary collodion process; when it is ready, remove it to a dish of water, agitate it a little, and then take out the plate, and wash it well under a gentle stream of water; allow it to drain for half a minute, and then pour on some of the prepared albumen, let it flow over, and drain off at one corner; repeat this four times, and each time pour off at a different corner, taking care to avoid bubbles and dust. A good plan to adopt is to have two thin beaker glasses of the same size, and a small funnel fitting into one of them (Fig. 3, A), plugged with a bit of fine sponge; pour the albumen from the plate into this funnel, the sponge will filter all bubbles, etc., and leave it clear; when all the albumen has been used out of B, change the funnel to B and pour from A; the albumen may thus be used three or four times over. When the albumen has well drained from the plate, dry it at a fire or stove, the prepared side towards the fire; when cool, store away in plate-box.
In this state the plate is not sensitive to light, and will keep good a very long time; it is consequently advisable, when all the apparatus and materials are in order, to prepare several dozens of plates for future use; from fifteen to twenty plates may be prepared in an hour, by arranging the different operations so as to lose no time between each in waiting. The preparation of the plates should be conducted in the dark room, until the albumen has been poured on, when they may be exposed without injury to daylight.
To render the plates sensitive, immerse for about half a minute in the aceto-nitrate bath, then place in a dish of water, and afterwards wash very well under a stream of water, and rear up to dry; when quite dry, put them in the dark frames and plate-box; or, in case of travelling, the plates may be packed together, a sheet of clean writing paper between each, and well wrapped up in several folds of paper; packed in this way they will keep good three or four weeks, even in very hot weather.
The exposure required varies according to the view to be taken, the amount of light, focus of lens, etc. For a picture of a well-lighted landscape, Rosse's orthographic lens with medium stop being used, about five minutes are sufficient; some views would require even two or three times as much, but a trial or two will give more information than as many volumes written on the subject.
Development of the Image.--Remove the plate from the dark frame, and pour water so as to wet all the surface; then place it face upwards on the levelling stand, and pour on from the developing cup some of the pyrogallic solution; pour this off and on once or twice, and then allow it to remain for a few minutes; then pour it off, and mix with it three or four drops of the silver developing solution, and pour it on and off again several times; the image will now appear, and keep gaining intensity until finished. Should the development be very slow, a little more of the silver solution should be added; but as little silver should be used as possible, as it is apt to decompose the pyrogallic solution, and turn it black, when it must be thrown away, and the plate washed before fresh solution is used.
As in the collodion process, an underdeveloped negative has the lights and shades in too great contrast, one over-exposed has too little; much may be done in the development to remedy this. Pyrogallic acid develops the image, nitrate of silver intensifies it. To fix the image, place the plate in a dish containing the hypo-solution; when the blue film has disappeared, wash well with water and rear up to dry, and afterwards varnish with the French varnish.
The above process is much longer in description than in practice; it requires care and patience, but with these and the use of suitable chemicals, success is certain; and when one considers how valuable is a good negative, on account of its power to produce an unlimited number of prints, superior to any drawings in beauty and accuracy, the time taken in its production is marvellously short.JOSEPH SIDEBOTHAM.