How I print gum

I make no claims of originality for my method, as it is the traditional recipe I learned from Keepers of Light years ago, and have no wish whatever to be the guru of yet one more gum printing cult. I simply give it here to show that (1) gum printing isn't nearly as difficult or complicated as it's sometimes made out to be, and (2) many different effects can be achieved by the same very simple formula. A thoughtful observation of the images on this site should make it clear that this simple method is extremely versatile; it can produce prints of high contrast or low contrast; high key, low key or full tonal range; dark and heavily pigmented or pale and subtle; relatively sharp and detailed or soft and impressionistic, and everything in between, as desired.

This page provides an outline; I cover most of the elements in more detail on separate pages that can be accessed by clicking on the link naming that particular element.

Negative: I don't attach any particular significance to the negative, as I've used every kind of negative imaginable; see link for a listing of some of them and links to gum prints made from them. To me the crucial elements in gum printing are the printing variables; the negative plays a rather insignificant part in the production of a gum print in my experience.

Paper and sizing: My current favorite is Arches Bright White paper, sized with gelatin hardened with glyoxal.

Emulsion: 1 unit gum/pigment: 1 unit saturated ammonium dichromate. No added water, no other ingredients.

Saturated ammonium dichromate: 27 g ammonium dichromate mixed into enough water to make 100 ml solution.

Gum/ Pigment Mix: I premix gum and watercolor paint to color saturation for each particular paint, using 35mm film canisters as containers to keep these stock mixes. I then either use the mix as is, or dilute it to different strengths for different applications (more about pigment concentration).

Coating: I brush the emulsion on the sized paper with 2-1/4 inch varnish brush, smooth with dry 4-inch hake, dry with hair dryer, expose immediately.

Exposure: EBV photoflood bulb. My exposures run 2-5 minutes, depending on pigment mix and ambient humidity.

Development: I still-develop for as long as it takes for the image to reach the desired level of development. This is most often 45 minutes to an hour, but can vary either way. I don't do any brushing or other manipulation of the image.

Drying: I dry the hardened gum with a hair dryer, then hang the print by clips on a line to dry the paper.

Clearing: I clear only when there is visible dichromate stain, which almost never happens in my usual practice. When necessary, I clear with either 5% potassium metabisulfite or 5% sodium bisulfite (there's no functional difference between them) after the print is dry.

Copyright Katharine Thayer, all rights reserved

Process Notes