by Gordon J. Holtslander

Note : Information on processes was taken from Arnow's Handbook of Alternative Photographic Processes and Crawford's Keepers of the Light


Calotype

Paper is coated with silver nitrate and potassium iodide, forming silver iodide. Prior to use the coated paper is recoated with a solution of gallic acid, silver nitrate and acetic acid. The gallinonitrate greatly increases sensitivity. When dry it is exposed to ultaviolet light. It is developed with more of the gallinonitrate of silver solution. The image is fixed with a weak hypo solution.

Hazards

• Sodium thiosulphate (hypo) will release highly toxic sulfer dioxide gas if heated or if acid is added.

Precautions

• Do not add acid or heat sodium thiosulphate

Albumen Print

Paper is coated with a thin layer of albumen and sodium or ammonium chloride, and then floated on a silver nitrate solution. When exposed to ultraviolet light the image prints out without need for development. To obtain a better color, and to preserve the image, the print is usually toned with gold chloride.

Hazards

The salting solution contains glacial acetic acid, which is highly corrosive to skin, eyes and mucous membranes, and can cause respiratory problems from repeated inhalation of vapours.

Silver nitrate is moderately corrosive, eye contact can result in blindness.

Precautions for Albumen Printing

• Wear gloves and goggles when handling concentrated acids.
• Avoid skin and eye exposure and wear goggles when handling silver nitrate. Do not inhale the dusts.

Cyanotype

The cyanotype relies on the reaction of ferric or iron salts to light, where they are reduced to the ferrous state. The ferrous salt reacts with the potassium ferricyanide to from insoluble ferric ferrocyanide, also known as Prussian Blue. Separate solutions of ferric ammonium citrate and potassium ferricyanide are made. Just prior to exposure equal parts of the solutions are combined and the paper is coated. Once dry the paper is exposed to UV light. The image is developed and fixed by rinsing the paper in warm running water for about 10 minutes. The image will gradually darken as the cyanotype completely oxidizes. The print can be oxidized by placing in a solution of 3% hydrogen peroxide. Other colors are possible by toning with a number of solutions.

Please see article Toning Cyanotypes

Hazards

• Ammonium citrate and pottasium ferricyanide are only slightly hazardous. Pottasium ferricyanide if exposed to intense heat, hot acid, or strong ultraviolet light may decompose and release highly poisonous hydrogen cyanide gas.

Precautions for cyanotype

• Do not add heat or acid to pottasium ferricyande and keep away from sources of strong ultraviolet light.
• Never mix ammonia and bleach which form lethal gases.
• Wear gloves and goggles when handling ammonia solutions, and use good ventilation.
• If ferric ammonium citrate is used frequently, avoid skin contact.

Kallitype

The kallitype is an iron-sensitive process that uses silver to form the image. The kallitype emulsion is a mixture of ferric oxalate and silver nitrate, with the addition of either oxalic acid or potassium oxalate. When exposed to light the ferric oxalate is changed to the ferrous state, which reduces the silver nitrate to the metallic silver. When developed the ferrous oxalate is dissolved and the metallic silver is left forming the image.

The kallitype process is a very unforgiving one, great care must be taken. The resulting prints are quite similar to platinum prints, however kallitype prints are not nearly as permanent as platinum, although substantially cheaper to produce.

Hazards

Silver nitrate is corrosive to the skin , eyes and mucous membranes, eye contact can cause blindness. Oxalic acid and ferric oxalate are highly corrosive. Gold chloride used for toning is a moderately irritating compound that can cause severe skin and respiratory allergies. The developer may contain potassium dichromate increasing skin and respiratory hazards, causing skin and respiratory allergies and ulceration. Potassium dichromate is a suspected human carcinogen. The fixer contains ammonia which is highly irritating to the eyes and respiratory system.

Precautions for Kallitype Printing

• Wear gloves when handling silver nitrate. Do not spray on silver nitrate sensitizer unless done in a spray booth.
• Wear gloves and goggles when handling ferric oxalate or oxalic acid solutions. Mix solutions in a fume hood or inside a glove box, or wear an approved toxic dust mask.
• Wear gloves whenhandling potassium dichromate or pottasium oxalate. Mix solutions in a fume hood or inside a glove box, or wear an approved toxic dust mask.

The Platinum and Palladium Print

The platinum and palladium print is considered by many to be the finest monochrome printing process. Platinum prints are capable of producing a long rich tonal scale, tremendous depth of shadows and the subtlest highlight details.

The platinum print is another iron sensitive process. Two sensitizing solutions and a platinum solutions are made:

• a ferric solution of oxalic acid and ferric oxalate
• a ferric-chlorate solution of oxalic acid and potassium chlorate
• a platinum solution of potassium chloroplatinite

The three solutions are mixed together just prior to coating. Different concentrations of the sensitizing solutions can be used to vary the contrast of the resulting emulsion.

The paper must be coated using a brush with no metallic surfaces (reacts with platinum). After drying the paper is exposed to ultraviolet light. The paper is developed in a solution of potassium oxalate. The image develops instantly so the print must be immersed in the developer instantly. The print is then cleared in three succesive baths of, for instance, hydrochloric acid clearing solution.

When the ferric salts are exposed to light, they reduce to the ferrous state. When the image is developed in pottassium oxalate, the platinum reduces to to the metallic state, where it has been exposed and in contact with the ferrous salts. The image is first formed by the iron and then by the platinum after development. Unexposed platinum and ferric salts are dissolved out. All traces of iron are removed by the clearing bath, leaving an image formed entirely of platinum.

Platinum prints are one of the most permanent printing media. The major disadvantage of platinum printing is the high cost. Palladium reacts almost exactly the same as platinum, and the two printing media are quite similar. Palladium prints are much warmer than platinum. The process details for palladium are almost identical, with a few minor changes. Palladium is substantially cheaper than platinum.

Hazards

Platinum salts are irritating to the eyes, skin and respiratory system. These chemicals are capable of causing skin allergies and platinosis a severe form of asthma. The sensitizer, developer, clearing baths and some of the toning solutions contain highly corrosive acids and oxalates that have signifigant skin, eye, respiratory and ingestion hazards. The oxalate developer, which is saved and reused, picks up metals from the paper and becomes more toxic with use.

Precautions for Platinum and Palladium Printing

• When handling pottasium chlorate, especially when combining it with hydochloric acid, work in a fume food or wear an approved respirator with a gas cartridge
• Store pottasium chlorate seperately and away from heat and combustable material.
• Do not use glycerin for local toning, because it creates an explosion hazard when combined with potassium chlorate
• Wear gloves and goggles when handling when handling platinum or palladium salts. Mix in a fume hood or inside a glove box, or wear an approved toxic dust mask
• Wear gloves and goggles when handling when handling oxalic acid or oxalate solutions. Mix in a fume hood or inside a glove box, or wear an approved toxic dust mask

Gum Bichromate Print

In gum bichromate printing the paper is coated with gum arabic which carries a pigment, and is sensitized with a bichromate. On exposure to UV light the bichromate causes the exposed gum arabic to harden and become insoluble in proportion to its exposure. The areas not exposed to light remain soluble.

The print is developed by floating it face down in water. The unexposed portions dissolve taking the pigment along. The insoluble portions remain on the paper. The print can be manipulated while developing, allowing the printer to make many local modifications. Any watercolor pigment can be used allowing the printer to choose the color of print. It is also possible, though very challenging to make full color prints using multiple printing with different colored pigments and color separation negatives.

In order to get a good print it usually necessary to multiple print, that is to coat, expose and develop the same print repeatedly to develop a full tonal scale. This requires some sort of registration technique. See the article Substrate Gum Method for a method of registering Gum Bichromate prints.

Gum bichromate printing can be very demanding because of its flexibility. The final gum bichromate image is usually somewhat soft.

Hazards

Pottasium dichromate and ammonium dichromate are moderately irritating to skin and highly irritating by inhalation. They can cause severe allergies and ulceration, and are also suspected carcinogens. Ammonium dichromate is flammable and unstable in the presence of many other substances. Many pigments used are moderately to highly poisonous, and can cause chronic poisoning from inhalation and accidental ingestion.

Precautions for Gum Bichromate

• Handle gum arabic carefully, avoid inhalation of dust. Wear gloves if allergic.
• Wear gloves and goggles when handling dichromates. Brush rather than airbrush or spray onto paper.
• Store ammonium dichromate seperately and away from sources of heat
• Wear gloves and goggles when handling ammonia solutions. Use good ventilation
• Avoid toxic preservatives such as formalin or mercuric chloride
• When choosing pigments, choose the least toxic. Use tube pigments rather than powdered pigments. If powders are used avoid grinding or spraying
• Wear gloves or use tongs throughout development to avoid contact with dichromates and pigments dissolving from the gum.

Carbon Print

A tissue is coated with a gelatine solution carrying a pigment sensitized with a dichromate. When it is exposed to light the gelatin hardens and becomes insoluble. The gelatin hardens only on the surface, to counteract this the exposed and washed tissue is placed firmly on a final support and then peeled away, transferring the image to the final support. This leaves the image flipped over on the final support and exposes the unhardened gelatin.

The transfer tissue is the temporary support that holds the gelatin pigment mixture during exposure. After exposure the gelatin and pigment are transferred to the final support. There are no current manufacturers of transfer tissue. The pigment transfer tissue can be made by hand. This makes the carbon process somewhat complicated.

A pigment tissue is made by coating a support with a mixture of gelatin and pigment and other a number of other ingredients. After the pigment tissue has been coated it is sensitized with a dichromate, and left to dry. The pigment tissue is the exposed to UV light. The dichromate causes the gelatin to harden where it is exposed to light.

After exposure the tissue is soaked for a few minutes to allow the excess dichromate to dissolve out and to allow the tissue to flatten. The tissue and final support are placed face to face under water and aligned. The two sheets are then carefully pulled out of the water, placed on a flat sheet (glass) and lightly squeegeed together.

The sheets are then weighed down for about 20 minutes. The two sheets are then placed in water at about 40 degrees C. The soluble gelatin and pigment will begin to ooze out. After another minute, carefully peel the pigment tissue off the final support. At this point there is no visible image on the final support, it consists of a mass of undissolved gelatin and pigment.

The final image is developed by agitating in all directions the final support in water in a number of baths, until the image is fully developed. The image develops by the unhardened unexposed gelatin dissolving in the water. The exposed gelatin is hardened by the dichromate and made insoluable in water. After development is complete the image is immersed in cold water to harden the gelatin. The resulting image is made up of only gelatin and pigment, making the carbon print one the most archival processes.

Hazards of Carbon Printing

The sensitizer contains pottasium or ammonium dichromate, which are both moderately irritating to skin and highly irritating to the respiratory system. Dichromates can cause skin and respiratory allergies and ulcerations. They are both suspected human carcinogens. Ammonium dichromate is flammable and unstable when in contact with many materials. The hardening bath conatins formalin which ismoderately irritating to the respiratory system, causing severe skin and respiratory allergies including asthma. Formalin is poisonous if ingested and is a suspected human carcinogen.

Precautions for Carbon Printing

• Wear goggles and gloves when handling pottasium dichromate or sodium dichromate.
• Mix powders in a fume hood or dust box, or used an approved toxic dust mask.
• Keep ammonium dichromate away from sources of heat and store seperately from other chemicals.
• Wear goggles and gloves when handling formalin baths. For large amounts use a local ventilation system.

UltraStable

The UltraStable process is a direct descendant of the original tricolor carbon process. While the original process used several transfers and manual registration techniques, this new incarnation makes the possibility of obtaining beautiful permanent color images much more easily.

The UltraStable process makes use of pre-sensitized pigment sheets. There is no messy and dangerous handling of dichromate and the shelf-life of the materials is about one year at room temperature or longer if refrigeration is used.

This process is relatively new. A computer is used to generate color separation negatives from the original image. The original image is first digitized by using a high resolution scanner. Computer software is used to produce four half-tone separation negatives of the same type used in the printing industry. The closer the dots are printed together the darker the image appears. This is the same technique used to print images in books and newspapers only much more refined. One can get wonderful separations and screened negatives with a high resolution scanner and printer. The process can also be (and is) used with optically produced continuous-tone negatives.

The exposure of the pigmented sheets and the development is very similar to carbon. The main difference between the Ultrastable process and the traditional carbon process is that the former uses convenient pre-sensitized pigmented sheets on dimensionally stable polyester sheets so that automatic registration is possible. The main drawback is that screened negatives are required and most people will have to use a service bureau to have them made.


Carbro Print

In carbro printing a pigment tissue similar to that used in Carbon printing is brought in contact with a bromide print. The gelatin in the pigment tissue loses its solubility through the chemical reaction between the sensitizer on the pigment tissue and the silver in the bromide print. The tissue is then transferred to the final support and developed in the same manner as a carbon print.

The advantages of a carbro print is that the pigment tissue is never sensitive to light and a UV light source in not necessary since the bromide print is made using traditional silver-gelatin methods.

Most bromide prints made today are coated with a hard surface to protect the fragile gelatin underneath. It is not possible to use these papers in carbro printing. Common unsupercoated papers currently available are: Kodak Polycontrast Rapid RC matte surface, Luminos RD Matte Bromide, Agfa Portriga Rapid No. 118, SupreBrome Royal Portrait Matte Paper, Ilfobrome Semi-Matte paper.

Hazards of Carbro Printing

The main hazardsof carbro printing result from exposure to the bromide developer and to the sensitizer for the carbon tissue. The developer can be a skin irritant causing allergies. The sensitizer for carbon tissue contains potassium dichromate which is moderately irritating to the skin and highly irritating by inhalation. It can causeskin allergies and ulceration. It is also a suspected human carcinogen.

Precautions for Carbro Printing

• Use the least toxic bromide developer.
• Do not heat or add acid to sodium thiosulphate
• Wear gloves when handling dichromate sensitizer. Mix in a fume hood, glove box or wear an approved toxic dust mask.
• Avoid inhalation of pottasium bromide powders.
• Wear gloves when handling solutions during transfer and development of the carbon tissue to avoid skin contact with pottasium dichromate and pigment suspended in gelatin.

Bromoil Print

Bromoil printing begins with a normally developed silver print. A non-hardening developer, such as amidol or Ethol LPD, is preferred for processing. Subsequent bleaching and tanning of the print removes the silver and results in selective hardening of the gelatin. In other words, the non-hardened areas of the print (the highlights) will absorb water and repel ink. The hardened parts of the print (shadows and mid-tones) will accept ink, resulting in a positive image resembling the original print. The advantages of bromoil are that (a) it allows a considerable degree of control over final image quality and (b) it is permanent.

The bleaching/tanning solution is made of distilled water (1000 ml), into which 70 ml of 10% solution copper sulphate, 70 ml of 10% solution potassium bromide, and 30 ml of 1% solution potassium dichromate is added. This solution will bleach out about a dozen 5x7 prints.

The ink used in bromoil printing is similar to lithographic ink. Hard ink is used initially, followed by soft ink, although the former alone will result in a lovely effect resembling etching. Brushes are specially-made of either hog, bear or fitch hair. A source for materials is provided at the end of this article.

The inking process involves first soaking the matrix (what the original print is called after bleaching and tanning) in water to induce the differential swelling of the gelatin. Test strips are used to determine optimal soaking times, starting with five minutes and continuing up to about 20 minutes. The test strips should be completely free of surface water before applying ink. The strip that accepts the ink most easily, with good buildup in the dark areas and clear highlights, will determine the proper soaking time.

The matrix is then soaked for the determined time and the surface water removed (using a damp chamois). The matrix is then placed upon a support and ink is applied. The inking process requires considerable practice to master the technique and involves lightly coating the surface, pushing the ink into the shadows and mid-tones and out of the highlights. The matrix may have to be re-soaked several times during the inking process, especially if resin-coated paper is used. The final print is allowed to dry for several days before matting and framing.

Hazards

Potassium dichromate and potassium bromide are moderately irritating to skin and highly irritating by inhalation. They can cause severe allergies and ulceration, and are also suspected carcinogens.

Copper sulphate??

Ink??

Precautions for Bromoil Printing

Use the same precautions followed in silver printing.

If amidol is used as the developer, then mix the solution outside the darkroom since the powder can become airborne and contaminate paper, resulting in purple stains.


Polaroid Transfer

The Polaroid transfer uses Polaroid peel apart color films in an unconventional manner. The Polaroid pack is peeled apart during processing, the positive image is transferred to an alternative surface. The surface the image is tranfered to imparts a different quality to the image. A receptor sheet is prepared, this will hold the final image. If paper is being used it is thoroughly soaked, other media can be used such as silk and other textiles.

The Polaroid negative is exposed, recording a new image, or by projecting a previously made slide onto the Polaroid. The film is processed in the pack as normal except the film is peeled apart after about 10 seconds. The negative containing all the dyes is then placed on the prepared receiving sheet. The negative is then firmly pressed onto the receptor sheet using a roller or your hands. It is critical to use even pressure. After waiting 90 seconds to two minutes the negative is peeled off the receptor. The dyes have now been transferred to the recieving sheet transferring the image to the receptor sheet. The quality of the transferred imaged depends on the method of transfer and the nature of the receptor sheet. A wide variety of papers and textiles can be used for receptor sheets.

Polaroid makes a variety of peel apart films in different sizes. Transfers will not work with black and white polaroids or with the SX70 style instant polaroids or other "integral" film types.

Hazards of Polaroid Transfer

The main hazard of Polaroid films is exposure to the highly caustic processing jelly, which contains sodium hydroxide or pottasium hydroxide. It remains at a high pH on the discarded portion (the non-image and negative area) for up to two hours. It is highly corrosive to the skin eyes and mucous membranes.

Precautions for Polaroid Transfer

• Avoid skin or eye contact with residual processing fluid.
• Dipose of wet negatives in a closed waste container to prevent further contact.
• If children chew or ingest film flush with water and contact a poison control center.