Edited by J. Traill Taylor
The future historian of photography will scarcely fail to record that the year 1874 was one of decided progress. Scarcely had its advent been made when a Liverpool gentleman-Mr. W. B. Bolton-whose name will ever be honourably associated with the introduction of the collodio-bromide process, published, through the medium of THE BRITISH JOURNAL OF PHOTOGRAPHY, and improvement he had effected upon that preparation which leaves scarcely anything more to be required. In emulsion processes such matters as the character of the pyroxyline, the nature of the preservative, and whether it were correct that free bromide or free nitrate be left in the film, had long been vexed questions which had given rise to writing, to a great deal of personal recrimination, and to disquisitions possessing scarcely any more interest for the general body of photographers than do essays on the Greek particles for the general public.
All these were swept away at one blow by the revolution of January, 1874, owing to which we have, at the time of issuing this ALMANAC, a collodion process possessing the following valuable features:- A collodion emulsion may now be prepared, by any person choosing to be at the trouble of doing so, by which a sensitive plate may be obtained by the mere act of pouring the emulsion upon it-no bath, no washing, no preservative of any kind whatever being required. A plate this prepared will keep as long after the preparation as any other dry plate. The sensitive emulsion will keep good for a reasonably long time after it has been made ready for use; but, not only so-it can also be made quite dry, like isinglass, in which state it will presumably keep good for years, enabling one to store a large supply in the leaves of a pocket-book ready for used at any time by dissolving a portion of it in ether. This is surely and most emphatically “photography made easy.” In improving the details of popularising the practice of this washed emulsion process the name of Captain Fox must be honourably mentioned. Interesting and practical articles by both the gentleman named, among others on the same subject, will be found elsewhere in this work.
Closely allied to the foregoing is the progress that has been made by Mr. Kennett in perfecting his sensitive gelatine pellicle, the main feature of which is the preparation of the sensitive gelatine in a dried of parchmentised form, in which state it will keep for years, ready for use when a portion of it shall have been dissolved in warm water. The plate, when coated with this and dried, will keep for a considerable period. A second feature is the extraordinary sensitiveness of plates thus prepared. The great majority of the failures experienced when using gelatine plates have arisen from this property; photographers seem never to have been able to realise the fact that it is possible to prepare dry plates quite as sensitive as wet ones; and this had led to carelessness in respect of the amount of light present in dark room when handling them, and, above all, to an excessive degree of over-exposure in the camera. Full directions for preparing gelatine plates were published in the last ALMANAC; the best method of developing them will be found in one of the pages devoted to formulae in another portion of this book.
Photography has, in the most marked manner, asserted its utility as regards astronomical science during the transit of Venus across the sun’s disc on the 9th of December last. Upon the correct observation of this phenomenon depends our knowledge of the distance of the sun from the earth and, consequently, of the dimensions of that orb. Owing to the great distance of the sun, the smallness of the earth, and the consequent impossibility of obtaining a base-line sufficiently long to enable tow observers separated from each other to obtain solar parallax, the distance of the sun could not this be ascertained; but, by taking advantage of the passage across the sun’s disc of a body comparatively close to us, the distance of which is known, and by noting exactly, and from stations very widely apart, the instant the passing body is seen to come in contact with and leave the solar disc, over which it passes like a dark spot, the whole matter is brought fairly within the grasp of the arithmetician. But the eyes of observers may deceive them, especially at a moment when the excitement must be very great; hence the desirability of employing eyes devoid of nerves and which own to no excitement save that produced by chemical means. By the agency of photography and the use of appliances for exposing plates in rapid succession-commencing a little before the time it was know the planet would come in contact with the sun’s discand, further, by noting the exact instant when each photograph was taken, it is obvious that not merely an accurate but a permanent record would be made; and this photography has effectually accomplished. The ingenious apparatus which was so much employed in photographing the transit of Venus has recently been fully described and illustrated by engravings in THE BRITISH JOURNAL OF PHOTOGRAPHY.
The reproduction of negatives by what has aptly been termed the “dusting-on” process forms a chief feature among the novelties of the past year. It has been well known for many years that certain mixtures of bichromate of potash and hygrometiric bodies were affected by light in such a way as to leave the surface of a plate which had been coated therewith in a state of greater or less deliquescence or tackiness in inverse proportion to its exposure to light; but the use that had been made of this discovery was mainly confined to the preparation of enamels, by developing a picture on opal glass or enamel by dusting or brushing over such a surface, after exposure under a transparency, any vitrifable powder. Thus a positive produced by a positive, the very obvious fact that a negative would produce a negative image was subsequently realised; and this was followed by an extensive practical application of the latter discovery in the direction of reproducing negatives.
Mr. Werge, too, has utilized the principle above spoken of in a very ingenious and most successful method of printing backgrounds of any artistic or other character in portrait negatives previously lacking in such an attractive feature. A portrait negative taken in the studio with a plain background may, by this invention, be handled over to the printer balcony, street, or marine scene. Instead of being held in reserve and sold as a secret process, Mr. Werge has worked out this valuable method of effecting the foregoing improvements and presented it freely to the public.
The “year that’s awa” must also be connected with a new and very important method of printing, based upon the combinations of oxalic acid and iron and their action as reducing agents of certain metals. Starting with the view of making photographs in the most stable metals he could think of-such as platinum or iridium-Mr. William Willis, jun., sought to find a good reducer if these metals, and spent some time in making experiments with ferrous oxalate-a beautiful lemonyellow powder known to be insoluble in water and most other menstrua. Working away for a considerable time without any satisfactory result Mr. Willis eventually discovered that a solution of it in the neutral oxalate of potash instantly precipitated the metal from the ordinary chloride of platinum; in other words, he found that a solution of ferrous oxalate in potassic oxalate reduced salts of platinum to the metallic condition. Now, as ferrous oxalate can be produced by the action of light upon ferric oxalate, it follows that if the paper which has received a wash of chloride of platinum and ferric oxalate be exposed in the printing frame, and then receive a wash of potassic oxalate, the metal will be reduced in proportion to the action of light. I have seen several pictures produced by Mr. Willis by the process here indicated; they were very beautiful, and withstood the destructive tests to which ordinary prints on albumenised paper succumbed.