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Alternative Photography: Anthotype

Anthotypes and cyanotypes are both ways of printing an image onto a piece of paper using light. Objects or a negative are used to block light from hitting certain areas of a piece of paper coated with a light-sensitive chemical. The light causes a chemical reaction in the coating, causing an image to form. Images produced by laying objects over a light sensitive surface like this are called photograms.

An anthotype is an image made with photosensitive extracts from plants. In this case I'm using curcumin extracted from turmeric powder with isopropyl alcohol. The bright yellow curcumin degrades (relatively) rapidly when exposed to ultraviolet light. Unexposed curcumin will react with sodium tetraborate to form a dark brown organo-metallic complex. After exposure, the image can be developed by reacting the unexposed curcumin, where it was shielded from the light, with sodium tetraborate (found in Borax powdered detergent). Anthotypes are particularly cool because all the ingredients are fairly safe for anyone to use and available at most grocery stores.

Cyanotypes are made by a similar principal, but with different chemicals. The photosensitive chemicals, potassium ferricyanide and ferric ammonium citrate, react when exposed to UV light to form Prussian blue dye, which has a deep blue color.

The cyanotype process is sensitive enough to reproduce photographs, although they won't have the same level of detail as darkroom photos or digital images (at least mine didn't). Notice that with the turmeric anthotype, the exposed areas of the paper turn light, but with cyanotypes the exposed areas turn dark. That means the anthotypes can reproduce a positive image, but cyanotypes require a negative to produce a positive final image; more on that later.

Anthotype Photo-Sensitive Solution

Combine 1 teaspoon turmeric powder with about 4 teaspoons of 91% isopropyl alcohol in a tall, thin container. Shake the container to mix and allow the solids to settle to the bottom. The liquid should be a clear, deep yellow/orange. Pour off the liquid and coat a sheet of watercolor paper with a foam brush. It will take a about half of the liquid to thoroughly coat one piece of 9x12 inch paper. Allow the paper to dry in a dark place away from direct sunlight, such as a closet. A fan will help it dry faster

Anthotype Printing and Developing

After the paper is dry, lay it on top of the cardboard backing. If you're making a photogram with thin items, such as leaves, place them on top of the paper and lay the Plexiglas on top. Clamp the whole thing together with the binder clips. Take your paper-sandwich to a sunny spot, either a flat surface outside or even a sunny windowsill. If you're making photogram with bulky objects that don't fit under the glass, lay them out on top of the 'sandwich.'

It will take a 2–3 hour exposure in direct sunlight to make a good image. You'll need to experiment a little to find the best exposure time.

To develop the anthotype, dissolve 2 teaspoons of Borax in about 1/2 cup of warm tap water and drizzle this over your image. You should the see unexposed parts turn to a dark brown. Once your image stops changing color, rinse the paper thoroughly to remove any excess Borax.

Cyanotype Photo-Sensitive Solution

A quick note on mixing chemicals: Both of these chemicals are relatively safe to work with, but please use caution. Dispose of any utensils and containers that have touched the chemicals after you're done and wear disposable gloves while working with them. Ingesting either of these chemicals or letting either contact your skin directly may cause health problems. Small amounts of chemicals may be disposed of down the drain, but consider taking any large amounts (ex. over a gram) of unused chemical to a house-hold hazardous waste disposal day (check you're town government website to find where/when the next one is). Here are links to the Safety Data Sheets (SDS):

https://pubchem.ncbi.nlm.nih.gov/compound/14457.

Anyone can work with these chemicals safely as long as they follow simple and commonsense precautions.

Mix 40g of potassium ferricyanide with 500ml distilled water. In a second container, mix 100g of ferric ammonium citrate with 500ml distilled water. Tightly cap both and shake until each is completely dissolved. These will keep indefinitely as long as they are stored away from sunlight. In a dim room, combine equal volumes of each solution in a small bottle and mix thoroughly. Once combined, the solution is fairly reactive to light, so only mix what you will immediately use. You don't need to mix much, I've found that ~1/2 teaspoon of sensitized solution is enough to coat one 9x12 inch sheet of paper.

Cover a work surface in newspaper or paper towels and coat the watercolor paper with a foam brush. Metal will react with these solutions so make sure your brush has no metal components. Let the paper dry in a dark place; a fan will help speed this up. While drying, the paper may arch up. This is fine, it will flatten out again once it's completely dry.

Cyanotype Printing & Developing

While you're preparing to print, work with the coated paper in a dim room away from direct sunlight. Wait to expose the paper to the sun until the very last minute.

After the paper is dry, sandwich it between the cardboard backing and Plexiglas as with the anthotype. To print an image, place your negative between the sensitized paper and glass. Carry it upside-down while walking to your sunny printing spot and lay it glass-side up.

For a cyanotype, 3–4 minutes of direct sunlight will be enough to create a good image. It may take a few more minutes on a cloudy day. Again, you'll need to experiment a little to find the best exposure time. I like to clamp a small square of thin cardboard under one of the binder clips in order to compare exposed and unexposed parts of the paper without disturbing the composition. The area under the square will remain bright green, while the exposed areas will turn dark blue/green.

Developing:

After exposure, rinse the paper under tap water until the unexposed parts are white and all the green solution is removed. The unexposed sensitized solution is soluble in water and is rinsed away. The exposed solution has reacted to form Prussian blue dye, which is insoluble in water and remains embedded in the paper. To immediately make the shadows darker, dunk it in a dilute hydrogen peroxide solution after an initial rinse in plain water (1 part 3% hydrogen peroxide solution plus 7 parts water works well). It will eventually darken on its own when exposed to air, but it's cooler to see the sudden color change.

If your cyanotypes start to fade after a few months or years, put them in a dark closet for a few days. The dye will 'recharge' and the dark blue color should be restored.

Making Negatives

In order to print a photograph with the cyanotype process, you need to make an negative. Cyanotype is a contact printing process, which means that the final image will be the same size as the negative. This is different than traditional darkroom techniques in which small negatives on a roll of film can be enlarged onto a bigger piece of photographic paper.

To make the negative for the olde-time cowboy portrait above, I took a digital photo, loaded it into GIMP, set it to gray scale, and inverted the colors. Once you open the photo in GIMP, go to the Image menu, select Mode, and set it to grayscale. Next, select the Color menu and click Invert. Finally, play around with the contrast and the brightness levels. Increasing the contrast will make a more striking photo with bright white highlights and dark blue shadows.

The resolution of the cowboy photo I used is actually lower than I would like. I recommend using a sharper photo than this.

Print out your negative on a sheet of computer printable transparent plastic.

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