Exposing lumen prints to sunlight

I’ve got heaps of outdated black&white photo papers from 1980s, some of them quite legendary brands like Agfa Brovira, Record-Rapid and Portriga-Rapid, and also Emaks and Varycon by Fotokemika. So I thought, instead of throwing them away, I might try lumen printing; a great way to use old and partly fogged papers.

Lumen prints are essentially plant photograms, printed with sunlight. Printing resembles normal contact printing, but the “negative” is a plant, sandwiched between a glass plate and a photo paper, and the exposed paper is not supposed to be developed but will print out a visible image during the exposure (like “real” printing-out papers do).

Lumen print on outdated Emaks paper, toned with Tetenal Gold Toner.

Of course, these papers were originally not made for this purpose, and to form an image without developer you need to expose for a very long time even in the brightest sunshine. The more UV light you get the faster are the exposure times. Different manufacturers’ papers can be very different in sensitivity to UV light. In these tests exposures ranged from half an hour to 7-8 hours.

After the exposure the print is washed in water shortly, and then fixed. Normal modern photographic fixers lighten the print considerably. Even when used standard sodium thiosulfate fixer for POP the lightening effect may be strong. In that case it is advisable to tone the print in gold or platinum/palladium toner before fixing. Normal final print wash follows after the fixer.

This is also on Emaks paper, toned with Tetenal Gold Toner. Emaks is quite slow – the exposure here was more than seven hours in bright sunlight. This paper can produce fabulous red, orange and bluish colors right after the exposure, before fixing, but the colors are not permanent. They will desaturate, and the print will lighten disappointedly unless toned before fixing.

Essentially fresh plants (not dried) should be used in lumen printing. Juices extracting from plants have an important part in reacting with photographic emulsions, forming special colors and effects.

There are methods for estimating the strength of UV radiation on each day, from which (and with a little experience with the light sensitive materials) one can judge if the exposure is going to be long, or very long.

An inexpensive UV detector can be used for measuring day-to-day UV index. Also local weather forecasts often include information of UV levels.

Jalo Porkkala: Convallaria Majalis #5, lumen print.

Centennial from Chicago Albumen Works is genuine printing-out-paper. It doesn’t need to be developed, and inherently produces good maximum blacks with much shorter exposures than my home-made pop papers. This is an untoned, fixed Centennial print.

More on lumen printing
by Jerry Burchfield