The process I've chosen to investigate further is the gum bichromate process, I'm particularly intrigued by the soft look it produces, creating images that seem-painting like. I've attached images created through this process on the side of my blog.
"Gum bichromate (or dichromate) printing involves creating a working emulsion made of three components:
- Gum arabic
- A dichromate (usually ammonium or potassium)
- Pigment
The emulsion is spread on a support, such as paper, and allowed to dry. A negative or matrix is then laid over top the emulsion and exposed to a UV light source. Usually a contact printing device or a sheet of heavy glass to ensure even, constant contact is employed. The light source will harden the dichromate in proportion to the densities of your negative. After exposure, the paper is placed in a series of plain water baths and allowed to develop until the unhardened portions of the emulsion have dissipated.
Materials
- Gum arabic
A bottled, predissolved, commercial brand should work fine, especially for the beginning printer. Check your local art shop or graphic arts supplier. Later you may wish to make your own by dissolving 30 grams of powdered gum to 90ml (or less) of very warm distilled water. Refrigerate to extend its shelf life thereby reducing the need to add a preservative. - a dichromate solution of either (choose one) ammonium or potassium
To make a near saturated solution (29%) of ammonium dichromate, add 29 grams to 100ml of very warm distilled water.
To make a near saturated solution (13%) of potassium dichromate, add 13 grams to 100ml of very warm distilled water.
My preference favors a potassium solution. Potassium dichromate, widely used in other processes such as carbon printing and photogravure, provides reasonable exposure speeds while minimizing the tendency to leave an orange stain. Should you choose a very strong UV source, a weaker solution may offer better control of your exposures. I use a 5% solution of potassium dichromate. Either compound can be purchased in a bright orange crystal granular form from a chemical supplier. Handle with care and take proper safety precautions; keep out of reach of children; consult a Material Safety Data Sheet (MSDS) for further handling instructions. - Water-soluble pigments
Virtually any brand of watercolor will provide at least a few pigments that will be suitable for gum printing. Some pigments may stain your paper resulting in flat, low-contrast prints with ruined highlights. However, you may find the staining effect suitable for certain images. For your beginning work try cadmiums, cobalts, ultramarines, earth pigments, and lamp black. You might try a mixture of Prussian Blue with Burnt Sienna as an alternative to single black pigments. - Brushes
The gum bichromate emulsion is essentially a modified watercolor. As such, I recommend investing in a few good quality watercolor brushes (flats or wash brushes; 1" and larger). Unless you enjoy plucking stray hairs out of your sticky emulsion, hake-style brushes might better be reserved for other artistic purposes. - Paper
Again, the gum bichromate emulsion is essentially a modified watercolor. Therefore, begin experimenting with watercolor papers that can handle repeated washes. In my opinion, you have two basic choices.
First are watercolor papers that can be classified as “old school” in that they utilize tried-and-true gelatine as a key sizing agent. Size, a term used in paper manufacturing, is a paper additive designed to regulate how and to what degree moisture will interact with the paper’s fibers. Gelatine is a very effective size and one that many gum printers continue to use today with excellent results. Papers that are gelatine sized sometimes need additional size applied to the surface followed by an application of a weak formaldehyde or glyoxal solution (hardener) to help maintain paper quality throughout multiple print layers and many water baths. Again, consult a MSDS for handling instructions if using either hardening solutions" (Blackburn).
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| William Henry Fox Talbot |
A contemporary artist that uses the gum bichromate process is Vivian Van Blerk, who "[b]y inventing fictions that unfold in parallel worlds close to our own, his photography exploits our tendency to read photographs as truthful documents. To make these photographs Vivian employs many medias. Sometimes he arranges found objects before the camera while for other images he will entirely construct, sculpt, model, and paint a scene and its actors. He also collages and montages imagery in the studio and darkroom, often retouching negatives and using alternative printing techniques to make strange his photographic universe."(http://jnfagrandtour.com/)
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| Vivian Van Blerk |
Works Cited
Blackburn, Peter J. "An Introduction to the Gum Bichromate Process." Web log post. Alternativephotography.com. N.p., n.d. Web. 22 Sept. 2015.
http://jnfagrandtour.com/vivian-van-blerk http://www.metmuseum.org/toah/hd/tlbt/hd_tlbt.htm
