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 XII.
NORMAL OR, PLAIN COLLODION, IODIZED COLLODION, BROMO-IODIZED COLLODION.

NORMAL or plain collodion is a solution of pyroxyline in a mixture of ether and alcohol, ready for being iodized or bromo-iodized. This sort of collodion when preserved in well corked bottles becomes clearer with age, and the sediment occupies continually less space. After it has stood for a week or two, the clear supernatant solution is decanted by means of a syphon, syringe, or stop-cock from the residue of undissolved pyroxyline beneath, and again put aside to settle. There is no fixed rule, arising from chemical equivalents or combining proportions, by which to institute a fixed formula for the preparation of normal or plain collodion. I have selected those which may be relied upon.

In another vessel shake together thoroughly--

As soon as the pyroxyline is completely covered and saturated with the alcohol, add the mixture of alcohol and ether, and shake well until the cotton has completely disappeared. Cork the vessel carefully, which is supposed to be full, and put it aside in a cool, dark place for a week or two, as before directed.

If a glutinous collodion, or a collodion with more body be desired, such as is required in the transfer of the collodion film upon glazed leather, etc., as much as fifty parts of pyroxyline may be dissolved in the above proportions of alcohol and ether; on the contrary, if a thin collodion be required for the flowing of large plates, the proportion may be as low as thirty-six or forty parts of the prepared cotton. Normal collodion for present use may be filtered; but it is far from being as pure by filtration as by subsidence. Filters for such purposes may be procured of the photographic establishments, by which the filtration proceeds without the contents coming in contact with the atmosphere. The above proportions are for the preparation of what is denominated alcohol collodion, which produces a soft, short, and structureless film on the glass plate.

Bromo-iodizing Solutions for the same.

Or,

Or,

Or,

Dissolve the salts in each case in the given quantity of alcohol, shaking the mixture frequently, and preserve it in well-closed bottles and in a dark place.

Collodion for photographic purposes is prepared from a mixture of plain collodion, and one of the bromo-iodizers above given, in the proportion of ten parts of the former to one of the latter. The mixture requires to be placed aside for a day or two, before it arrives at its maximum sensitiveness.

Many operators prepare their collodion directly with the requisite quantity of iodizing and bromo-iodizing materials, of which the following selection contains some of the best formula.

Formula of Lieut.- Colonel Stuart Wortley.

The pyroxyline is first steeped in the bromo-iodized alcohol, and the ether then added. These proportions produce a very fluid collodion, which is quite an advantage in coating large plates, where a very even film is required. It is said to be well adapted for instantaneous pictures. The sensitizing bath, which is used with this collodion, will be found amongst the list of silver baths given hereafter.

Ommeganck's Formulas for Portraits and Landscapes.

For Portraits of short exposure.

This collodion is sure to be thick enough; if too thick, however, it can be rendered more fluid by the addition of an appropriate quantity either of ether or absolute alcohol. If more than one tenth of the original volume be added, it will be necessary to mix with this the corresponding quantity of the bromo-iodizers.

For Landscapes, Views, and Direct Transparent Positives.

In this, as also in the preceding formula, weigh out the salts first; put them into a bottle of the proper capacity; add the alcohol, and dissolve them by frequent shaking; next add the ether and mix; finally introduce the pyroxyline in small flocks at a time, and shake until the cotton is dissolved. After the solution is effected the collodion is put aside in a cool, dark chamber, and allowed to settle for a couple of weeks. The first collodion will keep for a long time; the latter is less stable, but more sensitive to certain colors of foliage.

Formulas of Disdéri.

N0. 1.---COLLODION FOR WINTER.

First Formula.

Second Formula.

The iodide and bromide of potassium are dissolved in the smallest quantity of water. A quarter of the prescribed quantity of alcohol is poured into a clean bottle; the pyroxyline is then introduced, and the mixture is well shaken. After this operation the ether is added. The salts of iodine and bromine are next weighed and dissolved in the remaining quantity of alcohol, and then mixed with the solution containing the cotton. The collodion is put aside for a day or two, and then either decanted or filtered.

COLLODION FOR SPRING.

Second Formula.

COLLODION FOR SUMMER.

For copying engravings, etc., all that is required is a very simply iodized collodion, without any bromide.

Formula for Copying Collodion.

The collodion film, whether iodized or bromo-iodized, is rendered sensitive by immersion in a bath of nitrate of silver, which will be described in the following pages.

(Owing to the instability of collodion when once iodized, it has been proposed to invert the operations, and to mix with the collodion an equivalent quantity of the nitrate of silver, instead of the iodizers or bromo-iodizers, and then to sensitize the film in a bath as follows:

As soon as withdrawn from this bath, the collodion plate is washed in distilled water, and either used immediately by immersing it in a weak solution of nitrate of silver, or put away to dry. This process is due to Ch. D'Orma, and remains to be tried.) Whatever may be the difference of the composition of the collodion, arising from the variety of formulas that exist-for there is scarcely a single operator that does not boast of his own formula-each collodionized plate, when the film has sufficiently dried, is submitted to the chemical influence of a solution of nitrate of silver, in order to obtain by double decomposition in and on the film an iodide, or a bromo-iodide of silver, which is sensitive to the actinic influence of light. If the film contained a pure iodide, or a pure bromo-iodide of silver, without the presence of a nitrate, the results would not be satisfactory. The nitrates, or nitrogenized organic substances seem to be essential as accessories in the photographic operation of producing collodion positives and negatives. The most important salt in photographic chemistry is nitrate of silver; it is the salt from which most of the other silver salts are obtained, and is besides a very costly article, and deserves therefore to be treated with all due respect. Hence the following chapter is devoted to its service chiefly.