Photography in the Studio and in the Field / A Practical Manual Designed as a Companion Alike to the Professional and the Amateur Photographer

by Edward M. Estabrooke

In the first place, we will take up for consideration the positive process.

The first positives on glass were called ambrotypes, and were the successors to the daguerreotype, which they superseded and displaced by the superior facility of their production.

For the same reason the ambrotype was succeeded by the ferrotype, which was a positive collodion picture, made on a thin iron plate with a black japanned surface.

The ferrotype or tintype is now about the only product of the positive collodion process of considerable importance, and is the only one that will receive consideration in these pages.

Ferrotype plates are sold by all dealers in photographic materials; they are mostly manufactured by two large concerns in Worcester, Mass. p16

COLLODION FOR POSITIVES.

As has before been stated, to produce the finest results in positive photography requires certain modifications of the collodion bath and developer, which, while not unfitting them altogether for negative work, yet would render them quite unsuitable for high class work.

The formula for positive collodion here given has many merits, and among those is a certain quality of film, which might be termed opacity, but not in the strict sense of the word; it is that quality in the film which enables it to cover up any small scratch or water mark on the surface of the plate that would infallibly spoil the picture, if almost any other collodion were used.

This quality, with great clearness or transparency in the shadows, and a beautiful gradation of light and shade, make it unique as a positive collodion.

There may seem to be a contradiction between the terms opacity and great transparency of shadows, which may need further explanation. As the shadows of a positive collodion picture are produced by the black surface of the plate showing through the collodion, any defect on that portion of the surface would be expected to show very plainly, and it does so with the use of the ordinary collodions sold by the dealers, but not so with the collodion under consideration, which may be because it is less permeable by the silver solution, and that consequently the deposit of iodide of silver lies more on the surface and less within the texture of the film, and is thus kept from contact with organic matter or other defects on the surface of the plate; in some such manner only, can I account for a very valuable quality that has saved thousands of p17 plates, that would under other usage have been thrown away.