You are almost certainly familiar with this process, being one of the very first methods invented to capture an image onto a substrate for permanence. You may have seen a blue-print, or you may have seen cyanotype artwork prints, as they are not uncommon even today.

Discovered/invented by astronomer and scientist Sir John Herschel in 1842, it was originally used to create “photograms” (images of objects in silhouette on a substrate), most famously represented in the series of cyanotype limited-edition books, starting just a year after Herschel’s discovery, documenting ferns and other plant life from Anna Atkins’ extensive seaweed collection.

The procedure (and those below) involves working with chemistry  theory and experience - creating a solute compound of potassium ferricyanide and ferric ammonium citrate; and the addition of chemicals such as potassium dichromate and others as needed for particular outcomes - then applying this mildly photosensitive solution to a receptive surface such as paper or cloth (hereafter referred to as “support”). Cyanotypes can be printed on any surface capable of soaking up the iron solution. Although watercolor paper is a preferred medium, cotton, wool and even gelatin sizing on nonporous surfaces have been used.

The image is produced by exposing this sensitized support to a source of ultraviolet light, as a contact print. The method used for all of the alternative printmaking by this artist is done using natural sunlight. After development the non-water-soluble Prussian blue pigment remains in the paper. This is what gives the print its typical blue color.

Toning a cyanotype print involves additional steps that prepare the pigment for a chemical/physical change (mostly using tannins) to alter the hue of the image to various shades of blacks, browns, greens and so on. Much can and will go wrong with the process, especially at the toning steps, usually resulting in a staining of the substrate which renders the outcome a failure.

Considering all of the variables involved, (this is true for each of the processes described here), it may take a dozen or more attempts to render the one print considered satisfactory by the artist.

Most, if not all, of the alternative prints created here use a contact-printing process beginning with the creation of a negative image printed on a transparent or opaque media, then placing this negative on the sensitized support and exposing to the UV rays provided by the sun. In keeping with the historical methods used in these processes, the negative is prepared on paper, which is afterwards oil-rubbed to render it transparent (as opposed to printing on clear transparency media). This process does degrade image sharpness by a small degree, but supports this artist’s intent.

Gum Arabic Contact Printing

This process uses a different chemistry but also results from the exposure of a UV sensitized emulsion to sunlight, blocked to varying degrees with a transparent or opaque negative. An emulsion is prepared using gum arabic, a pigment, and potassium dichromate, that is painted onto the support and exposed and developed. The exposed areas become insoluble relative to the degree of UV exposure, the remaining areas are washed off during the developing step. This process lends itself to layering of different colors (or layering of the same color for contrast and other effect), much like a multi-color lithographic print is processed. The end result can be a full color print, or a mono-chromatic one.

Gum bichromate, or gum dichromate as it is also known, was invented in 1839, when Mungo Ponton discovered that dichromates are light sensitive. William Henry Fox Talbot later found that sensitized dichromated colloids such as gelatin and gum arabic became insoluble in water after exposure to sunlight. John Pouncy used colored pigment with gum arabic to create the first color images. Gum prints tend to be multi-layered images sometimes combined with other alternative process printing methods; I often incorporate cyanotype. The support needs to be heavy-weight cotton watercolor or printmaking paper that can withstand repeated and extended soakings. Each layer of pigment is individually coated, registered, exposed and washed. Separation negatives of cyan, magenta, and yellow or red, green, and blue are used for a full-color image.

Additionally, when I use a positive resist (instead of a negative), coupled with a white (or tinted) pigment and printed out on black paper, the resulting image is not unlike those done with chalk or pastel on dark support.

Carbon Transfer Print

This process is a very difficult and remarkably permanent printmaking method that can result in many failures before achieving one successful print. The process requires creating a gelatin-based “tissue” separately from the chemical process and exposure steps mentioned above.

The carbon process, initially a black-and-white process using lampblack (carbon black), was invented by Alphonse Poitevin in 1855. The process was later adapted to color, through the use of pigments, by Louis Ducos du Hauron in 1868. Carbon tissue, a layer of unsensitized pigmented gelatin on a thin paper support sheet, was introduced by British physicist and chemist Joseph Swan in 1864. Marketing began in 1866. Carbon tissue was a stock item in Europe and the US well into the 20th century, but by the 1950s carbon printing was very rare and supplies for it became an exotic specialty item. A carbon print is a photographic print with an image consisting of pigmented gelatin, rather than of silver or other metallic particles suspended in a uniform layer of gelatin, as in typical black-and-white prints, or of chromogenic dyes, as in typical photographic color prints.
In the original version of the printing process, carbon tissue (a temporary support sheet coated with a layer of gelatin mixed with a pigment - originally carbon black, from which the name derives) is bathed in a potassium dichromate sensitizing solution, dried, then exposed to strong ultraviolet light through a photographic negative, hardening the gelatin in proportion to the amount of light reaching it. The tissue is then developed by treatment with warm water, which dissolves the unhardened gelatin. The resulting pigment image is physically transferred to a final support surface, either directly or indirectly. A wide variety of colored pigments can be used instead of carbon black. It is now only found in the darkrooms of the rare enthusiast and a few exotic labs.

This process can produce images of very high quality which are exceptionally resistant to fading and other deterioration. It was developed in the mid-19th century in response to concerns about the fading of early types of silver-based black-and-white prints, which was already becoming apparent within a relatively few years of their introduction.

Using existing pigmented sheets and separations, one can prepare, print and process enough material, 60 sheets including the support, to produce about twelve 20" x 24" four-color prints in a 40-hour work week. However, this investment of time and effort can create prints of outstanding visual quality and proven archival permanence. Though carbon printing always has been, and remains, a labor-intensive, time-consuming and technologically demanding process, some of us prefer the high aesthetic of its remarkable beauty and longevity over all other processes.