In 1842, the distinguished British astronomer Sir William Herschel invented a technique for making accurate copies of his intricate scientific diagrams and calculations. It consisted of painting solutions of iron salts on paper, keeping the paper away from light until needed, placing the document to be copied (worked on translucent paper) atop it, and exposing it for several minutes to sunlight. The copy could then be washed in plain water to develop the image, and the resulting print—a white negative on deep blue background—would not fade with time or further exposure to light.
This method seems messy, inconvenient, and generally unsatisfactory in an age that depends on copy machines, quick-print shops, and one-hour photo-processing labs for speedy, inexpensive reproduction of almost anything in unlimited quantities. Yet for Herschel and his scientific circle, blueprints, also called cyanotypes, were a boon. No longer did notes and diagrams have to be laboriously copied by hand, with the attendant risk of introduced errors.
Anna Children Atkins, daughter of Herschel’s friend and colleague John George Children, was a botanist with a particular interest in algae. She was quick to see the application of this new process to her field. Then-current methods of recording and depicting plant life were hand-drawn illustrations and herbarium specimens—one very slow, the other impermanent, and neither particularly reproducible. She worked for a decade to create the first blueprint book, Photographs of British Algae: Cyanotype Impressions. Prints from this effort are still in excellent condition.
Though it’s possible to prepare your own surfaces for blueprinting with ferric ammonium citrate and potassium ferricyanide, treated materials are readily available by mail (see Sources). Our T-shirts came from Blueprints-Printables, a small company that offers shirts in a range of colors as well as cotton fabric by the yard and in small quilt squares. The printing process is quick and simple; the greatest challenge may be to find a sunny day.
• Treated T-shirt
• Sprigs of herbs (larger-leaved ones work best)
• Piece of corrugated cardboard large enough to pin the shirt to
• Straight pins
• Sunshine and fresh water
Our shirts came with explicit manufacturer’s instructions, but we learned a few tricks along the way specific to working with plant material. Here are the basic steps:
1. Remove shirt from its lightproof bag away from bright light and pin it flat to the cardboard.
2. Arrange herbs on shirt and carefully pin in place so that pins don’t show and no plant juice is released onto the shirt. We found that drying the herbs overnight in a thick phone book made them lie flatter and prevented moisture spots, which make permanent stains. Your herbs probably won’t lie perfectly flat on the fabric; the slight ghosting and shadows that they cast on the fabric are an attractive part of the design.
3. Take the shirt outside and prop up the cardboard so that it directly faces the sun. Leave it in the sun for 10 minutes (if the weather is warm and sunny) or 15 minutes (if it’s cool and sunny). If you leave it out longer on an overcast day, the design will be fuzzy because of the movement of the sun, and the background streaky.
4. Take the shirt inside, turn it over, and make a design on the back if you wish. You’ll have to expose the back to the sun even if you intend to leave it plain so that its final color will match that of the front. Return it to the sunshine and expose the back for the same length of time that you did the front.
5. When the entire shirt has been exposed, bring it in out of the sun and rinse it thoroughly until the rinse water runs clear. The design and background color will emerge as you rinse.
The blue-and-white shirt in the photograph on page 66 shows the traditional blueprint colors. The green shirt was predyed a bright emerald so that when the blueprint develops, the background becomes a dark blue-green while the pattern remains emerald. The brown-and-white shirt has undergone a simple but interesting transformation in which the blue is removed by washing in a phosphate detergent and the brown developed by soaking the shirt in a strong tea solution, whose tannic acid reacts with the iron salts.
Blueprinted shirts should be hand-washed in a phosphate-free liquid detergent. With this care, its patterns will remain clear and the colors strong indefinitely.
Blueprints-Printables, 1504 #7 Industrial Way, Belmont, CA 94002. (800) 356-0045. Fully treated cotton T-shirts are available, as well as shirts with a single treated circle on the front. Also cotton quilt squares, and silk and cotton yardage. Complete instructions included. For a price list and order form, send an SASE to the above address.
Sun Gardens, Victorian Pictograms, reproductions of Anna Atkins’s botanical blueprints. New York: Aperture Books, 1985.