Sci Fri: On the art of fixing a shadow

For this season’s final installment of Science Friday, we are going way back to the scientific roots of early photography and making anthotypes (sun+plants=photogram) and a camera obscura.

The formula is simple, but the anthoype activity is one of the more complex we’re doing with preschoolers here. It takes a fair amount of preparation and time to do this one, but it’s fun for kids of all ages to see how a simple photograph (“light writing”) is made.

The second activity shows the effect of basic optics, requires very little prep, and is wonderful to behold.

First, imagine a world without photography. A little weird, isn’t it? There were no exact visual replicas of anything; the closest one could get was a drawing or painting. (Of course, whether or not photography itself can create exact visual replicas is argued by those who study it.)

Next, a lesson in the history of photography because I love it so much. I’ll try to keep it short. Photography began with far more chemical experimentation than artistic intent. Three things were necessary for the invention of photography: the invention of the camera, theories of how to use light to make the pictures a camera could produce, and the availability of diverse and reasonably priced chemicals. These three came together in the early 1800s and several individuals, working independently, invented different forms of photography by about 1840.

In 1839, one of the first photographs used elemental silver as the light-sensitive material and was an image of a building and two windmills. Some other early processes used things like tar pitch (bitumen of Judea), petroleum, oil of lavender, pewter, iodine crystals, silver nitrate, mercury, table salt, acetic and gallic acid, hyposulphite of soda, iron salts and potassium ferricyanide, to name a few.*

©Copyright 2012, Maren Mecham

Gum Bichromate printing, my favorite process and one I wrote about previously, uses gum arabic, ammonium dichromate, and watercolor pigment. (Image, right.)

The anthotype process was invented by the Englishman Sir John Herschel in 1842. Incidentally, Herschel was good friends with my favorite early photographer, Julia Margaret Cameron. (Oh, the temptation to digress here is very hard to resist.) Herschel discovered that you could coat a piece of paper with plant dyes, place solid items thereon and expose to sunlight to make a photogram, or a picture of the shadows (or a photograph if using positive tonal film).

The materials are simple and the result is also very simple. Only a shadow remains and that shadow is not permanent. It can be displayed but is subject to fading over time. In today’s amazing world, that shadow writing is nothing very special. But any sort of semi-permanent image made by light was downright thrilling back in Herschel’s day. And my kids got pretty excited about their own light pictures last week, so it still holds some magic.

Materials needed for Activity 1: Anthotypes
• plants (spinach, kale, irises, berries, beets, onion skins, etc.)
• distilled water or denatured alcohol
• blender
• strainer and coffee filters
• thick watercolor paper (300lb) or archival rag board
• flat paint brush or foam brush
contact printing frame or piece of glass and heavy “pony” clips (the tighter the press, the sharper the edges of the image will be because the movement of the earth in relation to the sun…creates shadows…etc.)
• items for shadow-making: plants or other flat opaque items OR a high-contrast positive black and white film image
• sunlight
• patience

Activity 1: Anthotypes
I used the instructions by Photojojo on this page. There are also good instructions and information here and here about how to do it without using denatured alcohol. Supposedly it helps extract the chlorophyll from the plants but you might opt for distilled or demineralized water instead.

Here are the steps from Photojojo with my comments in green (and a mix of their instructional photos and mine):

“STEP 1: Transform the plant into emulsion

before Once you discover the plant that suits your fancy, it’s time to blend it up. (I used spinach, rugosa rose petals, raspberries, and frozen blueberries warmed in the microwave because blueberry skins give more color when heated.) In the case of spinach, use only the leaves and you will receive a darker pigment.

Splash some denatured alcohol in the mix. Alcohol is an ideal diluter because it helps extract the chlorophyll from the plants. Blend until it looks juicy.

Strain your mixture through a coffee filter or cheesecloth into a bowl. Drip, drip, drip. (Squeeze, squeeze.)


beforeBrushes with hair shed all over your paper, so you may try a foam brush. (I used a paint brush.)

Dampen your brush with water, so it doesn’t suck up all the plant goop. Dip it in your juice and coat your paper any funky way you like. Make sure you get it evenly spread out.

Since the sun bleaches the light areas of your positive, begin with as saturated a color as possible. This may require several applications. (I did mine by dim light at night and dried them in front of a fan before recoating. I made three coats of emulsion.)

Dry in a dark place to avoid premature exposing.

STEP 3: Frame it

Grab your positive film (or plants) and arrange it on top of

your dry piece of coated paper. (My boys had a great time finding, planning, and arranging their pictures.) Place it into your contact print frame and close it up tight.

You can also use a regular frame as long as the positive stays in place. Contact print frames are really the way to go if you can get a hold of one. They have a hinged back that lets you check the exposure without accidentally moving the positive.

STEP 4: Give it to the sun

Find a place in your yard that has the brightest sun and leave your soon to be anthotypes there to cook. Check on them periodically to make sure they are not being blocked by shadows.

Now it’s time to wait. The length of your exposure depends on the weather conditions, so if it’s an overcast day, give it more time. (Spinach was done in 4 hours, the rest were set out over two days for a total time of about 8 hours.)


Admire your print! Anthotypes are low contrast and produce a subtle and delicate looking print. From here, you’ll want to store it away from the sun. You might want to scan your anthotype. That way, even if it fades, you’ll be able preserve what it looked like forever.”



Making a camera obscura

Materials needed for Activity 2:
• a room with one window (preferably with a view of something like a street or nature)
• a window covering to seal out all light and with a very small distinct hole
• a blank wall or sheet of poster board opposite the window

The camera obscura, literally “dark chamber”, has been around for centuries. It consists of making a pinhole in a darkened room to see the image formed on the opposite wall. It was used to observe solar eclipses and to aid artists in their drawing or painting of the natural world. In Victorian times, it was fashionable to have larger public camera obscuras in cities or by the sea. Edinburgh, Scotland, still has one as do both San Fransisco and Santa Monica, CA.

What to do:
Using a window that faces an interesting scene (especially a street view or something with similar movement), cover all the incoming light. Make a very small hole in the covering as exactly round as you can and watch as the world unfolds in a real-time silent movie, upside down, on the opposite wall or on a piece of large poster board. We went over the optics involved using a simple diagram like the one above.

I remember discovering this effect at my high school. School was getting out for the day and I was in the theater awaiting play rehearsal. I was backstage by an exit door with a window that had been painted black. Someone had scratched a small bit of the paint away long ago, and now I watched the scene on the opposite wall as the buses loaded and students socialized and walked away, so quiet, so unaware of my voyeurism, the clouds and trees moving in the wind at the bottom of the frame…. We performed the experiment again in photography class in college, and I began showing it to my children when they were little and in need of simple activities.

Photographer Abelardo Morell made this great image of Central Park in fall using both a camera and a camera obscura. Brilliant. There are more of his images here. (Respecting copyrights, I won’t copy/paste them but they are REALLY worth the time to click and view.) At some point in his portfolio, he used a lens to invert the images coming through.

Here’s a nice little 2 minute preview of what this experiment looks like:

One of the most surprising things about doing this experiment is how much fun it is to view the world silent, upside down, in color, and moving. It’s a little surreal and yet it is exactly real. Technically, this is the kind of image that is formed in the back of our eyes on the retinas. Our brains are beautifully clever enough to flip the image right side up. Wild.

I hope you have enjoyed this series; we have certainly had a good time experimenting and reporting to you. Remember to “take chances, make mistakes, and get messy”!

Happy Science Friday!

*See “On the Art of Fixing a Shadow: One Hundred and Fifty Years of Photography”, Catalogue I

1 thought on “Sci Fri: On the art of fixing a shadow

  1. Wow! So enjoyed this post. As a photog mostly of the digital age, I feel so enlightened (no pun intended :). Must do these experiments with my kids this summer!

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