Printing Processes with Silver Salts

Printing can be by two methods:

Printing-out

Where the image is produced entirely through the action of light by exposing the printing paper, in contact with the negative, to light. It is useful to distinguish between the earliest photographic prints (Salt Prints and Albumen Prints) that were produced in this way and the later (emulsion) printing-out papers.

Developing-out

Where the latent image is developed by chemical action. This was used as early as the 1850s but did not prove popular. It was not until the late 1880s and 1890s that developing-out papers came to be widely used.

Supports

Paper

In Britain early paper, used in the salt print period, was produced by R. Turner, Chafford Mill, and J. Whatman, Turkey Mill. Whatman paper was later known as Hollingworth, reflecting the earlier change of ownership. On the continent papers were produced by Canson, Lacroix and others. By the 1870s most paper used in Europe was from the mills around Rive in France or from Malmedy (then in Rhenish Prussia) known as Saxe paper. The prominent manufactures being Blanchet, Fréres & Kleber (France) and Steinbach (Malmedy). The size used in manufacturing these early papers differed, French papers was generally starch based which produced different results to English papers that were mostly sized using gelatine.

Later, emulsion period, papers generally had an intermediate layer of baryta between the emulsion and the paper to give added brilliancy to the image, provide a smooth surface for the emulsion and protected it from impurities in the paper. Earlier, gelatine and albumen had sometimes been used as an intermediate layer.

Paper was produced with different surface texture (smooth, rough, silk, etc.), surface finish (glossy, matt), thickness or weight, and base colour (white, cream).¹

Glass

Clear glass was used for lantern slides and diapositives, opal glass which was popular in the 1880s was also used for positive images. The emulsion was usually gelatine silver bromide or chloro-bromide.²

Celluloid, Xylonite

These materials were used in the 1890s as a substitute for glass. Finishes were clear for making diapositives or opaque (this looked similar to ivory and was popular with the souvenir trade and for portraiture). As with glass, the finish could be smooth or ground. Since the material could be moulded, sheets with raised or convex sections were produced for portraiture.³

Toning

Early plain salted prints, when fixed with sodium hyposulphite (hypo), and albumen prints had a reddish colour and were usually toned to produce a brown (sepia) image. Later printing-out papers also produced a reddish or yellow image and were toned brown or purple-black. Bromide prints could be toned to change the naturally black image to a warmer brown tone.

Thomas Malone relates that at Talbot's Reading establishment salt prints were toned by holding a hot iron against them.⁴ Sulphur toning was used with silver chloride (plain salted) prints in the 1840s, gold toning was introduced in the late 1840s, both remained in general use. The contents of an old hypo bath were often utilised for sulphur toning.

Gold chloride became the most commonly used toner, replacing sulphur toning, for printing-out papers, platinum toning was less common. Bromide prints were not normally toned except where particular colour changes were required, toners included: lead; copper, for red tones; platinum, for brown to red tones; vanadium, for yellow or green tones; iron, for blue or green tones.⁵

Printing-Out Papers

The image is produced entirely by the action of light by exposing the negative, in contact with the printing paper, to light. The earliest photographic prints (Salt Prints and Albumen Prints) were produced in this way. Later, emulsion based, printing-out papers remained popular into the twentieth century. Emulsions were produced in different grades to match the density range of the negative.

Gelatine Silver Chloride

This paper was first described by Abney in 1882, shortly after this, paper was introduced commercially by Obernetter. Joseph Barker, seemingly unaware of Abney's work, announced a silver chloride process in 1885. The Britannia Works Co. (Ilford) introduced silver chloride paper in 1891 under the name of P.O.P. On the continent this type of paper was known as Aristotype.¹

Collodion Silver Chloride

This paper was first described by G.W. Simpson in 1864 and commercially introduced by Obernetter around 1867.²

Self-toning Paper

These papers contain gold or other salts in the emulsion which are reduced during fixing to tone the paper. A separate toning bath was not needed. They appeared commercially in the late 1890s but proposals were made as early as 1869. Both gelatine silver chloride and collodion silver chloride papers were produced.³

Developing-Out Papers

Development of the latent image applied to positive prints had been used in Blanquart-Evrard's positive process of around 1850, that process did not prove long-lasting and it was not until the late 1880s and 1890s that development of positive prints became popular. That period corresponded with greater use of small format cameras where enlarging was a requirement, for which the faster developing-out papers were ideal.

The same emulsion that was used on paper was coated on glass, ground glass, celluloid and Xylonite for lantern slides and transparencies and also on opal glass. Emulsions were produced in different grades to match the density range of the negative.

Gelatine Silver Bromide

This paper was proposed by Peter Mawdsley in 1874 and introduced by the Liverpool Dry Plate Co. It was several years, though, before other manufacturers followed: Morgan & Kidd, 1880; Mawson & Swan, early 1880s; Eastman 1882; Hutinet, early 1880s. The process became widely used during the late 1880s.¹

Bromide paper gave deep black tones, exposure was by artificial light, it could be handled by yellow light and was commonly used when enlarging.

Gelatine Silver Chloride

This refers to the later process with an excess of chloride and the use of a developing agent rather than the earlier silver chloride or salt print processes.

Gelatine silver chloride paper was first described by Eder and Pizzighelli in 1881 and was commercially introduced shortly afterwards.² Abney had made earlier experiments without success. Chloride papers came into wider use with the introduction of Velox around 1893 by the Nepera Chemical Co. (part of Kodak from 1898). Velox, invented by Leo Baekeland, was substantially different in its manufacture from the earlier Eder-Pizzighelli process.

The process could be worked in weak artificial light and became known as 'gaslight paper', exposure was by strong artificial light. It gave warm tones in a variety of colours dependent on the type of developer used.

Chloro-Bromide

This paper was first described by Eder in 1883. Chloro-Bromide papers were more sensitive than gelatine silver chloride and produced warm tones having the appearance of albumen prints. In Britain they were introduced by Ilford and known as Alpha papers. Gelatine chloro-bromide was commonly used on diapositives.³

Silver Phosphate

These papers were introduced around 1909 and met with limited success. Silver phosphate had been used earlier with salt prints and in some emulsion processes.

The paper was worked in subdued light and developed with a physical developer, exposure was by daylight or artificial light. Various tones could be produced depending on manipulation, gold toning was not necessary. In Britain these papers were sold under the Ensyna brand name by Houghtons.⁴

Kodak Standard Paper Numbering

In 1947 Kodak standardised the numbering of their paper products.

Base Tint	White, Ivory, Cream
Base Texture	Smooth, Velvet, Fine, Silk, Rough
Surface Finish	Glossy, Lustre, Matt
Weight	Light, Single, Double
Contrast Grade	0 - Extra Soft
	1 - Soft
	2 - Normal
	3 - Hard
	4 - Extra Hard
	5 - Ultra Hard

This was normally written as: Brand Name, Tint, Texture, Finish, Weight, e.g. Bromesko WSM.D the contrast grade was shown separately.