Just a bit of fun photochemistry… I’m not sure that this will lead to any serious art, but you never know!
A couple of definitions, before we proceed…
Photogram — an image made by placing objects on a photosensitive surface during exposure to light
Anthotype — an image made using photosensitive pigments derived from plants
The images shown below are anthotype photograms made using the spice turmeric.
Very briefly, I took some turmeric, added it to some 70% iso-propanol (rubbing alcohol) and stirred it around a bit. Next, I filtered the mixture through a paper towel to remove the solids. The resulting solution is a nice yellow-orange color. This solution was painted on to paper and allowed to dry. The paper becomes very bright yellow.
I then placed objects atop the paper, covered the stack with a piece of glass and exposed things to the sun (or in one case my UV light box) for a period of hours. The light bleaches the yellow pigment giving an image which is then stabilized (and made more contrasty) by dipping the paper in a solution of borax.
The first two images shown below are photograms I made yesterday. The first image is a two hour exposure using my UV-LED light source. The second image is a four hour exposure outside on an partly cloudy afternoon. Both were treated with borax (sodium borate) after exposure.
While these photograms were exposing, I returned to my roots as a chemist and did a experiment. I took strips of coated paper and dipped them into various solutions I had around for other processes. The results are shown in the third image below. The top of each strip is the unexposed, untreated paper showing the bright yellow.
Clearly borax is not only compound that can cause a color change in the tumeric yellow. Every basic solution I tried caused a color change, the two acidic solution did not cause a visible change. The ammonia solution (far right) turned the paper bright red initially. However, the color faded as the paper dried.
I continued my experiments today. The last five images are four hour exposures made today under mostly sunny skies. These were all treated with sodium carbonate (washing soda) after exposure.
In addition to making these exposures, I took the test strips shown in the third photo and placed them in the sun for about eight hours. There was little, if any, fading of the colors produced by treating with borate, carbonate or bicarbonate.
A note on the paper… all but the last two images shown were made using inexpensive, nothing special, drawing paper (Strathmore 400 or Strathmore Vison papers). The last two image were made using somewhat ‘fancier’ papers; Stonehenge Warm (Untiled #4) and Artistico HP watercolor paper (Untitled #5). The fancier papers seem to hold more pigment (especially the Artistico) and thus the images are darker.
Lastly, the large majority of this is not new (just Google ‘turmeric anthotype‘!). However, a quick search did not turn up any mention of bases other than borax to treat paper after exposure. Thus, that bit may well be new knowledge.
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“Someone” is having Too much fun on his retirement! Thanks for the chem lesson – glad there will not be a quiz on it:)
Seriously, these experiments with chemicals and paper are giving you amazing results.
So, have you settled on a chemical mixture of choice or will there be more experimentation? I think I know the answer – enjoy!!1
Comment by Joe Kennedy — 24 April 2021 @ 8:37 AM