How to preserve Chlorophyll prints

Bárbara Morais shares her process of preserving – otherwise unstable – Chlorophyll photographs, making them UV resistant.

Writer and photography / Bárbara Morais

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“Nature is the final place where memory lies.”

Mr. Binh Danh, the photographer who has made famous the chlorophyll prints, said that this is a whole process of attempts and errors, in which “only one in every five prints is successful”.

To make it even more “precious”, who makes chlorophyll prints knows the anguish of seeing the degradation of the image when exposed to the sun, aggravated with the fragility of the leaf itself. These facts give rise to the general idea of chlorophyll prints as a temporary photographic process, fragile, unstable – vulnerable to time.

But, can we do something to preserve chlorophyll prints? Binh Danh preserves them in two- or three-inch-thick blocks of resin. What kind of resin? I can’t find any information. So, I decided to look for techniques of preservation of leaves in the area of botany and culinary.

The technique that I present to you is the way I preserve my chlorophyll prints. I have little experience, yet. My leaves only have 4 weeks of existence, but they’re perfect!

How (and why) to do

Chlorophyll, the large molecule with a long tail and a body holding Magnesium atom at its center, gives vegetables the green color. High temperature, acidic medium, and exposure of the chlorophyll molecule to the cell’s own enzyme will result in the loss of the Magnesium atom or the tail, a prime reason for losing the green color.

The principle involved in this technique is to bring about a combination of the chlorophyll in the cells of the plant with copper. The resulting compound, copper phyllocyanate, is practically insoluble and isn’t destroyed by light. So, we need Copper Sulphate.

In slightly acidic medium, hydrogen atoms replace the magnesium atom of the chlorophyll pigment. One way to avoid losing the ‘bright green’ is to soaking leaves in a slightly alkaline water adding a pinch of baking soda since the amount of hydrogen atoms required to displace the magnesium is less. There is one drawback – adding excess of baking soda can turn the vegetable mushy.

Glycerin is used to preserve leaves without pressing, giving them a more natural appearance, soft and supple.

We will also need 95% alcohol, formalin.

1The most difficult part of the process is to get the copper into the cells before the chlorophyll escapes or breaks down. In order to accomplish this, the air of the tissues must be removed, by immersion in 90 to 95 percent alcohol for 20 minutes and then soaking for some time in boiled water (whit a pinch of baking soda for 4 liters of water) after the latter has cooled.

2Then, the leaves must be placed in a dilute 5% glycerol solution containing enough dissolved copper sulfate to give it a marked bluish tint. The solution should be boiled before using to free it from air.
At the time of using, enough formalin should be added to make the solution about 1%. The leaves should be left in this until all of the green parts have assumed a bluish-green color.

3They should then be removed to a dilute glycerin-formalin solution free from copper. This will gradually dissolve all the copper not in combination whit chlorophyll and thus bring out the natural shade and variations.
After thorough washing and clearing in this latter solution the material may be preserved, without change, in any of the common media except strong alcohol.

4At the end, I paint the sheet with UV-resistant varnish, so as to be able to expose the leaf to the sun running at less risk of damaging the image.

And this is my chlorophyll print, placed in a frame made of acrylic, which allows the visualization of the leave in all its dimensions!

Most relevant sites found

• “A Method of Preserving the Green Color of Plants for Exhibition Purposes”, by Woods, Albert F., Botanical Gazette, Vol 24, 1897.
  https://ia801905.us.archive.org/0/items/jstor-2464571/2464571.pdf
• “Preserving Flowers and Leaves”, Fact Sheet 556, by Francis R. Gouin. Department of Horticulture. The University of Maryland at College Park, 1994.
• How to preserve the Green Color in Vegetables – Foodanstatic
  http://www.foodantastic.com/preserve-green-color-vegetables

Bárbara Morais is a physician, living in the North of Portugal. A self-taught photographer is a lover of alternative photographic processes. She exhibited her photographs at the Order of Physicians-Oporto and won the first prize of photography of the Portuguese Association of General Clinic Physicians in 2015.