Again, consult a MSDS for handling instructions if using either hardening solutions. 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. Gelatine is a very effective size and one that many gum printers continue to use today with excellent results. 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. In my opinion, you have two basic choices.įirst are watercolor papers that can be classified as “old school” in that they utilize tried-and-true gelatine as a key sizing agent. Therefore, begin experimenting with watercolor papers that can handle repeated washes. Unless you enjoy plucking stray hairs out of your sticky emulsion, hake-style brushes might better be reserved for other artistic purposes.Īgain, 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). The gum bichromate emulsion is essentially a modified watercolor. You might try a mixture of Prussian Blue with Burnt Sienna as an alternative to single black pigments. For your beginning work try cadmiums, cobalts, ultramarines, earth pigments, and lamp black. However, you may find the staining effect suitable for certain images. Some pigments may stain your paper resulting in flat, low-contrast prints with ruined highlights. Virtually any brand of watercolor will provide at least a few pigments that will be suitable for gum printing. 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. Either compound can be purchased in a bright orange crystal granular form from a chemical supplier.
I use a 5% solution of potassium dichromate. Should you choose a very strong UV source, a weaker solution may offer better control of your exposures. 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. My preference favors a potassium solution. To make a near saturated solution (13%) of potassium dichromate, add 13 grams to 100ml of very warm distilled water. To make a near saturated solution (29%) of ammonium dichromate, add 29 grams to 100ml of very warm distilled water. Refrigerate to extend its shelf life thereby reducing the need to add a preservative.Ī dichromate solution of either (choose one) ammonium or potassium
Later you may wish to make your own by dissolving 30 grams of powdered gum to 90ml (or less) of very warm distilled water. Check your local art shop or graphic arts supplier.
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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.Ī bottled, predissolved, commercial brand should work fine, especially for the beginning printer. The light source will harden the dichromate in proportion to the densities of your negative. Usually a contact printing device or a sheet of heavy glass to ensure even, constant contact is employed. A negative or matrix is then laid over top the emulsion and exposed to a UV light source. The emulsion is spread on a support, such as paper, and allowed to dry. Gum bichromate (or dichromate) printing involves creating a working emulsion made of three components:Ī dichromate (usually ammonium or potassium) 3 glass containers for mixing ingredients.25 grams of Ferric ammonium citrate (green).
A white print emerges on a blue background. The cyanotype is printed using UV light, such as the sun, a light box or a UV lamp.Īfter exposure the material is processed by simply rinsing it in water. Objects or negatives are placed on the material to make a print. Paper, card, textiles or any other naturally absorbent material is coated with the solution and dried in the dark. The two solutions are then blended together in equal parts. Potassium ferricyanide and Ferric ammonium citrate (green) are mixed with water separately. The cyanotype is made up of two simple solutions.