Bromoil Process

In 1907, working from the research of Howard Farmer and E.J. Wall, C. Welbourne Piper publicised the working details of a process that produced an inked image from a silver bromide paper print. A non-supercoated paper print is treated in a dichromated bleach solution, converting the silver image back into silver bromide. The bleaching bath also hardens or tans the gelatine in proportion to the amount of silver present. The print is washed in water, swelling the gelatine into a relief matrix that will accept greasy ink in the shadow and mid-tone areas, but repel it in the highlights (where the water content is highest). Once the matrix has been drained and blotted, the original photographic image can be inked up with a large blunt-cut brush, or small rubber brayer. Bromoil transfer is a variant of the above wherein the inked matrix is printed onto a second sheet of paper. A mangle press or the back of a spoon can be used for the transfer, which is suitable for colour work as a series of selective matrices can be printed in register to produce a coloured image. (see Bromoil Video & other products, p.67).

The Process

Paper:

Kentmere Art Document bromide enlarging paper, contrast grades 2 or 3 Print the bromide print for both highlight and shadow detail, printing somewhat darker and flatter than usual. Develop, wash (do not use stop bath) and fix using the solutions below, and wash thoroughly.

Developer:

use a developer having a minimal hardening effect on the gelatine of the paper: Amidol and Sodium Sulphite, or: Kodak Dektol diluted 1 part developer to 10 parts water.

Fixer:

without hardeners. A basic fix should contain acidifiers but no hardeners. If in doubt, try Kodak F-24 non-hardening fixing bath or plain hypo (sodium thiosulphate) with sodium bisulphite. These fixers can also be used to fix the bleached print.

Bromoil bleaching bath:

15 g copper sulphate 15 g potassium bromide 1 g potassium dichromate Mix in 375ml. distilled water, then top up with water to make 500ml. stock solution. Store in a dark brown bottle, away from heat and light. Dilute for use: 1 part stock to 3 parts water. Bleach in the bleaching bath until the image is a faint beige colour, and leave in the bath for half again as long. Wash thoroughly and fix as usual. A grey-ish image should be barely visible. Dry the print, and store away from light.

Inking:

Adana letterpress inks or Charbonnel litho. inks. Add French chalk to increase tacky consistency, a solvent is extra-refined lighter fuel. Soak the print in water at 20°C for at least 10 minutes. Place the print face up on a paper towel to blot water off the back, then face up on a smooth waterproof surface. A tilted sheet of melamine or plexiglass is suitable as an easel. Blot the surface of the print (gently) with a damp chamois. Work over the print with brayer, covering entire surface quickly then more carefully redistributing and clearing highlights and mid-tones. Or, with a brush, start with a hard consistency of litho ink and hop this onto the entire surface of the print. Work over the print with shorter hopping strokes to redistribute the ink from the highlight to shadow areas. Once inked, the print will take about 24 hours to dry thoroughly.

Cyanotype

Invented by Sir John Herschel in 1841, this simple process gives a continuous-tone image of Prussian Blue using a sensitising solution of Ammonium Ferric Citrate and Potassium Ferricyanide. These iron salts, when exposed to natural or artificial ultraviolet light, are reduced to their ferrous state, producing a high contrast blue image when oxidised. Oxidation is hastened by immersion in running water, which also washes away the unused iron salts.

The Process

Solution A 65 g ammonium ferric citrate (green) in distilled water to make 250ml total.
Solution B 23 g potassium ferricyanide in distilled water to make 250ml total.
Note: distilled water is more commonly known as 'purified water'.
Store solutions separately in brown glass bottles, away from light. Filter before use, and mix in equal proportions A to B.

Printing.

Paper: For all alternative processes high quality art paper such as those used in printmaking or watercolour work are most suitable. Atlantis Silversafe 200g/sq m., Somerset Satin and Waterford Satin are good papers to start with, however it is advisable to make tests to find a paper to suit your requirements.

Coat:

in subdued tungsten light, and dry away from light and heat. Print by contact (in a printing frame with a full sized negative) in sunlight or by an ultra-violet light source until the shadows look bronzed. Allow at least one stop over-exposure to compensate for loss of density during processing.

Development:

immerse in running water, and wash until the chartreuse stain of the ferric ammonium citrate has completely disappeared. Take care to avoid excessive washing as this will to wash out the image.

Argyrotype

The inherent problem of the iron-based silver processes lies in the danger of leaving residual ferric iron in the print, to its eventual undoing as the image is attacked. The Argyrotype process, developed by Mike Ware, has been designed to avert this problem, and ingeniously uses a little known silver salt, silver sulphamate, manufactured 'in-situ'. The resulting acidic sensitiser can be washed out of the paper cleanly. Brief working details are included here, and we can supply the Fotospeed kit, detailed on this page.

Argyrotype Sensitiser

• Chemicals needed. (GPR grade ca 98%)
• Sulphamic acid 7.6g. Silver (1) Oxide 7.6 g.
• Ammonium Ferric Citrate (green) 23g.
• Tween 20 0.8ml (surfactant, assists spreading, poly-oxyethylene sorbitan monolaurate)
• Distilled water to make 100 ml.

Procedure for making up

Use subdued tungsten light.

1. Dissolve the sulphamic acid in about 700ml of distilled water at room temperature.
2. Add the powdered silver(1) oxide in small portions with vigorous stirring so that it dissolves over a period of about 20 minutes or so. (Ignore any grey crystals that separate out at this stage.)
3. Add the ammonium ferric citrate in portions with continuous stirring until it is dissolved. The solution will appear murky green at this stage.
4. Add the Tween 20, mixing well, and make it up to 100ml. with distilled water.
5. Filter the solution, and store it in a brown bottle, kept in the dark at room temperature.

notes

1. On storage, the sensitiser may slowly deposit a small amount of black solid. This does not significantly impair its strength, but if troublesome it should be filtered off.
2. To make a more contrasty sensitiser, an additional 10g of sulphamic acid may be added per litre of solution.

Coating and exposure

Coating is most easily done using a glass rod as spreader as under 'Coating Methods'. Dry thoroughly, as wet sensitiser will ruin a negative. Pre-humidifying the paper will give a cooler purple/brown. Not all papers are suitable, do some tests. One of the best is the smooth surfaced Atlantis 'Silver-Safe' cotton-fibre paper in 200 g/sq. m. weight. Printing is by contact, using Ultra-Violet or sunlight. Exposure time is likely to be 1 or 2 minutes in sunlight, and can be gauged to some extent by the degree of printing-out visible from the front of the contact frame, although a 'split' frame is a great help

Argyrotype processing

1. Immerse in running water (or 3 or 4 changes of static water) until the yellow background has disappeared, which will take about 5 mins.
2. Immerse in a 2% sodium thiosulphate fixing bath for about 3 mins. The image will cool.
3. Wash in running water (or static changes) for about 20 mins.
4. Drain and air dry. The image tones 'dry-down' somewhat.

notes

1. The dilute fixing bath will need replacement frequently. This should be carried out when the colour shift from orange to brown becomes sluggish.
2. Over-exposed prints may be 'reduced' by prolonging the fixing time.
3. Very delicate gradation in the high values may be obtained by leaving the exposed print in a humid atmosphere (100% R.H.) for about 10 minutes before wet processing.

Kallitype Process

This is an iron-silver process. In 1842 Sir John Herschel invented the chryso-type process, using a strong solution of ferric ammonium citrate as a light-sensitive coating on paper. Once exposed, the paper was developed up with silver nitrate (Herschel first used gold chloride), washed, and fixed in hypo (another of Herschel's many innovations). The latterly termed Argerotype process was not much used, but in 1889, W. J. Nicol based his Kallitype process on Herschel's work. Known as the 'poor mans platinum', the Kallitype had many complex and sometimes highly toxic variations. In its most basic (and least toxic) form, a light sensitive coating of ferric ammonium citrate and silver nitrate produces a sepia image of great richness.

The Process

Sensitiser

note: rinse all utensils in distilled water before use.
Make 3 separate solutions;

1. 6g Ammonium Ferric Citrate in 22ml distilled water
2. 1g Tartaric Acid in 22ml distilled water
3. 2.50g Silver Nitrate in 22ml distilled water

The tartaric acid should be freshly mixed just before combining the solutions to sensitise. The other solutions will keep in brown bottles, away from light. The ammonium ferric citrate solution may need to be filtered before use.Mix the first two solutions. Add the silver nitrate slowly, a few drops at a time, stirring well to be sure that there is no milky precipitate. Paper: Use a good quality art paper.Sensitise the paper by coating (see 'Cyanotype' for suggestions) in subdued tungsten light. Dry in the dark.

Printing:

Expose in sunlight or by ultra-violet lamp in contact under a negative until the image prints out. Do not overprint: the image will intensify during fixing. Wash in running water until all milky silver nitrate residue disappears.

Fixing:

12g sodium thiosulphate in 1 litre water
Fix until image reaches maximum density: beware of over-fixing, which will erode the image.Wash thoroughly in running water (up to 30 minutes if thick paper is used). Note: Iron-silver prints may be toned with gold toner as per (Talbot's) salted paper.

Salted Paper

William Henry Fox Talbot's original salted silver nitrate paper evolved between 1834 and 1839. Talbot used smooth writing paper washed in a weak solution of common salt, dried, then coated with a solution of silver nitrate, resulting in light-sensitive silver chloride. Once dry, the paper could be printed out in strong sunlight. The resulting image of metallic silver was fixed in a strong solution of salt. Talbot refined the process, and Sir John Herschel suggested sodium thiosulphate (hypo) as a fixing agent. Salted paper was the basis for Talbot's Calotype process, which used silver nitrate and gallic acid to develop up a latent image in the exposed paper, and is the foundation of modern silver-based photography.

The Process

Paper:

good quality art paper. Note: rinse utensils, etc. with distilled water before use.

Salting Solution:

1.8% solution Sodium Chloride (1.8g to 100ml. purified water) Salt the paper by soaking in the salting solution for about 2 minutes. Be sure to disperse any air bubbles that may form on the surface. Blot with photographic blotting paper, and allow to dry.

Sensitising solution:

3g silver nitrate to 20ml. distilled water 20% solution Citric Acid (saturated solution, 2g to 10ml distilled water)
Mix 3ml Silver Nitrate to 0.3ml Citric Acid - just before coating. Sensitise the paper in subdued tungsten light (see 'Coating methods').
Dry paper in the dark, then re-humidify over bath of washing soda or plain water.

Printing:

contact print by inspection in sunlight or under an ultra-violet lamp, until the image is 1/2 stop over-exposed.
Wash the print in running water until the milky silver compound has completely dispersed (2-20 minutes, depending on paper weight.

Fixing:

fix the print in a plain sodium thiosulphate fixer for 5-30 minutes (depending on the paper, as above). Wash in running water for 15 to 30 minutes, depending on the paper weight.

Gum Bichromate

In 1839, Mungo Ponton published a paper on the light sensitive properties of chromates. These are strong alkaline compounds that are available today as potassium or ammonium dichromate (bichromate is the older and more common term). In 1852, Fox Talbot used animal gelatine in combination with dichromate. He observed that the dichromated colloid hardened in proportion to its exposure to sunlight, and applied the principle to an early photogravure process. This work formed the basis for many later photographic and photomechanical processes. In 1894, A. Rouille-Ladevez redefined the process, producing prints for an exhibition at the Photo-Club de Paris. His work inspired photographers whose pictorial work derived from Impressionism in fine art, and great use was made of the gum bichromate process as a method of producing the painterly images so characteristic of turn-of-the-century art photography.

Materials

Gum arabic:

available as prepared liquid gum arabic (avoid acid preservatives) or mix dry gum (acacia) at 1 part to 3 parts water. Dissolve (overnight), strain, and add optional preservative (phenol based such as thymol, never formalin or formaldehyde)

Pigment:

water colour for transparency, or designers gouache or casein for more opacity. Powdered pigment should be ground with a small quantity of liquid gum arabic. Potassium Dichromate (bichromate) Ammonium Dichromate (bichromate) is capable of a more saturated solution, decreasing exposure time, but giving some problems of exposure control.

Paper:

a good quality, sized, art paper is recommended.

The Process

Potassium dichromate: make a 10% saturated solution (10g to 100ml distilled water) The solution will keep in the dark. If crystals form during storage, redissolve by warming the bottle. Mix gum solution and sensitiser in equal parts. Use as soon as possible. Add to prepared pigment.

Coat:

paper with a soft, broad brush, and allow to dry away from light and heat. The prepared paper will keep for several days in the dark, but works best when used as soon as possible.

Expose:

the paper to sunlight or a mercury vapour lamp by contact printing under a negative. Exposure time will depend on density of negative and type of light source, but always look for a brown print-out in the shadows and the start of the mid-tones. The colour of the pigment in the coating will also affect exposure time: blue and green requiring less time than red or yellow.

'Develop':

the print in a bath of tepid water. Slide the print into the water (face down). Soak (a few minutes to several hours, depending on exposure). Unexposed gum will dissolve, while gum hardened by the action of light and chromate will remain. Gum coating can then be removed locally by the application of a stream of water or gentle brushing. Flatten the wet print against a tilted, waterproof board to dry. The gum print can be overprinted by recoating (once dry), re-exposing and developing. Staining of pigment in the highlights can be minimised by the application of paper size, and the dichromate stain can be removed in a 5% potassium alum bath, or by re-soaking the finished, dried print in warm water.