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
|Water, (distilled,)||20 ounces.|
Soak the gelatine in the water until it has swelled, then apply heat to dissolve it. After it is cool, mix with the solution the white of an egg very intimately, then boil the mixture, so as to coagulate the albumen. Let it stand for a few moments, and then filter whilst still hot through a flannel bag before a fire. the first portions of the filtrate, not being clear, are poured back again into the funnel and again filtered. the alcohol is next added to the clear solution, in order to communicate to it keeping properties.
When about to use the gelatine, place the bottle that contains it in a dish of hot water, in order that the gelatine may melt; a separate vessel used for flowing the mixture is nearly filled with the melted gelatine, and rendered still more hot and fluid in a hot-water bath. the plate is first heated and then flowed with this hot solution, which is allowed to rest upon the surface a moment; fresh gelatine is then poured upon the plate, and off again at one corner, until the film is quite uniform. Drain the plate and dry.
The exposure, developing, and fixing are the same as in the preceding processes.
Dr. Hill Norris's theory of this process is as follows: the collodion film, as long as it is moist, is a porous material, and
when it when it is once dried, it ceases to be porous. Now, by the use of honey, gelatine, etc., on the moist surface, it is supposed that these substances penetrate the pores, and thus prevent the pyroxyline, during induration and drying, from closing up apertures which allow the developing solution to permeate the film. the special function of the honey, however, seems to be the removal of every trace of nitrate of silver.
This process promises to supersede most of the preceding dry methods. the collodion is apt to wrinkle or slide entirely from the plate, when prepared according to the original mode. There are, therefore, two methods of preparing the glass for the reception of the collodion film.
In the first place, and in all cases, file the edges on both sides of each plate. Then, if the plate is not first to be covered with a solution of gelatine, place it upon a flat surface, as on the corner of a table, and laying a flat ruler along either side, leaving one eighth of an inch between the edge of the glass and the edge of the ruler, abrade the surface of the glass along this narrow strip by means of a wet emery or corundum grindstone, such as is used by dentists. in this way a rough border will be made all round, to which the collodion will adhere with great tenacity.
The plates must be exceedingly well cleaned and free from all sorts of reduction from previous use. So prepared, they y may be manipulated without much risk of undergoing the troubles alluded to. But it is the opinion of many good amateurs in this department, that the plates work much better when previously covered with a coating of gelatine, which s acts not alone as a preventive to wrinkles, etc., in the collodion film, but is supposed in some way to ameliorate the photographic results during development, with all sorts of collodion. Small plates need scarcely to be covered with gelatine.
To prepare a clear solution of gelatine, proceed as follows:
|Acetic acid, (glacial,)||6 minims.|
|Water distilled||10 ounces.|
Immerse the gelatine in the cold water, and let it swell for two or three hours in a warm room; after which add the acetic acid, and apply a gentle heat until the gelatine is dissolved. To this add the following solution:
|Iodide of cadmium||12 grains.|
|Bromide of cadmium||3 grains.|
Filter the solution two or three times through paper in a warm place. So prepared, it will keep a long time, is limpid, and has, when warm, about the same consistency as collodion, but it does not flow over the plate with the same facility.
Warm the plates and the gelatine solution; then pour the latter upon the surface of the former, and cause it to spread, either by breathing forcibly upon it or by means of a glass triangle. the surplus quantity is poured off at one corner into a separate vessel, and after dripping, the plates are reared away against the wall on the same corner, upon bibulous paper, until they are dry. Spontaneous drying in a warm room is preferable to drying quickly by artificial heat. the plates so prepared can be preserved when dry in grooved boxes for an indefinite time.
A good bromo-iodized collodion, already ripe, and of a powdery nature is the best for this process.
Formula for Collodion.
|Iodide of ammonium||16 grains.|
|Iodide of cadmium||8 grains.|
|Bromide of cadmium,||16 grains.|
|Alcohol, spec. gray., .805||4 ounces.|
|Ether, concentrated,||4 ounces.|
After the plates have been carefully flowed with this collodion, they are sensitized in a bath of nitrate of silver, made slightly acid with acetic acid, that is, with one drop of the ordinary acetic acid to each ounce of the neutral nitrate of silver bath. for instantaneous work, or, properly speaking here, for very short exposures, a neutral bath would be the most appropriately calculated to succeed. When the color of the collodion film indicates a sufficiency of sensitization, which will be in four or five minutes under ordinary circumstances, the plate is taken out and immersed in a dish of distilled water, moved about for a short time, and then left collodion-film upward in the dish, until a second plate is collodionized and sensitized. It is then thoroughly washed under the tap with common water, and finally flowed with distilled water.
This solution may vary in strength from ten to thirty grains of tannin to one ounce of water, depending upon the light and the nature of the collodion.
|Distilled water||1 ounce.|
Dissolve and filter through paper before use, and then add four five minims of alcohol to the ounce of water, but always after filtration. of this solution pour first a small quantity upon the plate, so as to remove before it all superfluous water; pour it on and off two or three times, and afterward commence with a fresh solution. Allow the plate to drain for a minute or two, then rear it up on end upon a piece of blotting paper, and afterward dry spontaneously or by artificial heat, remote from all light. 'When perfectly dry, the plates will keep in the dark for a long time.
When the contrasts of the landscape are very marked, and the light brilliant, a less quantity of tannin may be used; the greater the quantity of tannin, the greater the density of the shades. When the plates are dry, the film, if in a right condition, will be bright and highly polished in its appearance.
If the tannin plates have not first been covered with a solution of gelatine, this is the time, before they are put away, to proceed round the edges of the film with varnish. This operation can be performed best by dipping the quill end of a strong feather from a hen's wing into the varnish, and then, inclining the feather, begin at one corner of the plate in contact with the edge and proceed to the other end slowly, so that a small quantity of the varnish is attracted by the collodion film as you advance. the side of the quill is in contact with the edge, and not the end. As soon as the varnish is thoroughly dry, the plates are stored away. It is best to use the plates as soon after preparation as possible.
The time of exposure is three or four times as long as with the wet process, but this may be shortened by following the plan of development recommended by Dr. Draper.
|No. 1||Pyrogallic acid||72 grains.|
|Alcohol||1 fluid ounce.|
Filter if there is a white precipitate, otherwise not.
|No. 2.||Nitrate of silver||20 grains.|
|Citric acid||20 grains.|
|Distilled water||1 ounce.|
Filter if there is a white precipitate, otherwise not. With No. 1 and No. 2 as stock bottles, proceed as follows:
|Dilute solution of No. 1.||Solution No. 1,||1 drachm.||For present use.|
|Distilled water,||6 ounces.|
Of this dilute solution of No. 1, take out four drachms for a stereoscopic slide, and add, to it from fifteen to twenty-five minims of No. 2. This mixture is made immediately before the plate is to be developed.
Immerse the dry plate for a few seconds in distilled water; then pour on the developer and keep it in motion until the image appears. If the picture is slow in making its appearance, although the sky develops quickly, the time of exposure was too short, and the developer must be increased in strength, by adding ten or fifteen drops of No. 1. On the contrary, where the time has been too long, the development on all parts will be simultaneous, and the proper equilibrium of action will have to be maintained by adding a few drops of No. 2, otherwise the sky will not be opaque enough.
Dr. Draper's modification consists in immersing the plates after exposure in a vessel of hot distilled water, and then proceeding as above. the development is very rapid. in consequence of this the time of exposure can be reduced almost to instantaneity.
It is advisable not to postpone the development long after the exposure; during the evening of the day on which the pictures were taken is in all respects an appropriate time for the development, and although in many instances this operation can be put off, it is not advisable. the color of the image by the tannin process is rich and warm; its tone is very agreeable. Plates prepared either by this process or by the albumen are well adapted for taking transparent positives, by direct contact printing, for the magic lantern, or for the stereoscope.
The developed plates are well washed and fixed in a bath of hyposulphite of soda, but not of the cyanide, because it is apt to loosen the film. They are then carefully washed so as not to disturb the film, dried and varnished.
Several modifications of the Tannin process have been proposed, more or less successful; the honey process of Mr. England being one which seems to possess considerable advantages in sensitiveness. Mr. England's formula for collodion is as follows:
To five parts of ether and three of alcohol, add sufficient Pyroxyline to give a tolerably thick film. As soon as it has well settled decant the clear supernatant part into another bottle, and bottle, and measure off two portions of ten drachms each; to one add forty grains of bromide of cadmium, and to thirty to one add forty grains of iodide of ammonium; shake till dissolved, and put by to settle. When thoroughly settled, add one drachm of each to six parts of plain collodion.
Sensitize in a neutral bath of nitrate of silver, containing Forty grains of nitrate of silver to the ounce of water, and warm afterward in a dish of distilled water, rendered acid by acetic acid. The plate is left in this dish until a second one is prepared; it is then taken out and washed thoroughly beneath the tap, flowed with distilled water, and coated with the following solution:
|Distilled water||1 ounce.|
Coat as before directed, wash and dry. Protect the edges of the film with varnish.
After exposure, immerse the plate in a bath of nitrate of silver, ten grains to the ounce, as follows:
|Nitrate of silver||2 drachms.|
|Distilled water||12 ounces.|
|Acetic acid||1 drachm.|
Keep the plate in this bath for one minute, and then develop with the pyrogallic acid developer as usual, or according to the method in the Tannin process just described.
Mr. Anthony, of New-York, finds it advantageous to fume the Tannin plates for a few seconds with the vapor of ammonia, for instance, the evening before their exposure, the time of which is said to be shortened by this process.
This is the simplest of all dry processes, the discovery of Despratz. It consists simply in dissolving in the collodion about two and a half grains of powdered resin for every ounce of collodion. After sensitization the plate is well washed and dried. the development and all other manipulations are the same as in the wet collodion process. Dubosq makes use of amber, and Hardwich of Glycirrhizine for the Same purpose.
The operations in this process, as furnished by Sutton, are as follows:
1. Clean the glass plate, dry it thoroughly, and apply to it a solution composed of one grain of India-rubber, dissolved in an ounce of keroselene.
2. Coat the plate thus prepared with bromo-iodized collodion, containing an equal number of atoms of iodine and bromine, added in combination with cadmium. There should be about five grains of mixed iodide and bromide of cadmium to the ounce of collodion.
3. Excite the film in a bath composed of thirty grains of pure recrystallized nitrate of silver, slightly acidified with nitric acid.
4. Wash off all the free nitrate of silver, and pour over the film a preservative composed of twenty-five grains of gum-arabic freshly dissolved in an ounce of water. Let it dry spontaneously, and, before putting the plate into the dark-slide, dry it again thoroughly before a hot flat-iron.
5. Give the same exposure as for wet collodion.
6. Develop the picture by first wetting it with distilled water, and then pouring over it a developer, consisting of one ounce of distilled water, two grains of pyrogallic acid, two scruples of glacial acetic acid, and a few drops of a weak solution of nitrate of silver. the image appears immediately, and very soon acquires the necessary intensity.
7. Fix the negative in the usual way, with a saturated solution of the hyposulphite soda or lime, and when dry, varnish it with spirit varnish.
This is a modification of the Tannin Process, or Tannin and Honey Process. the characteristic difference is this:
After the plate is sensitized, it is not washed, but flowed immediately with equal parts of a filtered, fifteen grain per ounce solution of tannin and gum, the latter consisting of four ounces of picked gum-arabic, dissolved in eight ounces of rain-water. the collodion plate requires twice the time in the nitrate bath of an ordinary collodion plate. When removed from the bath, drain a few moments and flow it with the preservative mixture bountifully, as with collodion, tilting the plate, so that the tannin solution flows from the right upper corner to the left upper corner, then to the left lower corner, and finally to the right lower corner, and then along with the excess of water off at this corner. Repeat the operation once or twice. the last lot can be used for the first of the next plate. the plate is then drained, washed and dried. It is said to be almost as sensitive as a wet collodion plate. It is soaked in distilled or rain-water before it is developed. It is fixed and developed like any other tannin plate.
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