No carbon, but still potatoes...

...well, some kind of starch anyways. Thanks to my collaborator-in-all-things-color Zach Long at the Image Permanence Institute, I can now show you photomicrographs of the Alticolor film with an expiration date of July 1956 that I recently acquired. Given the date, this is from one of the last batches of the last form of the screen process originally introduced as the Autochrome in 1907. As I mentioned before, I have heard rumors that, at some point, carbon black was no longer used in the manufacture of the Lumiere additive screen processes, and that yeast grains replaced potato starch grains. Well, this Alticolor film does NOT use carbon black to fill the interstices between the grains (see upper image), but it DOES still use starch grains (as evidenced by the Maltese cross in each grain under cross polars-- see lower image). While it would be nice to have a more complete picture of how the various "Autochrome" products changed over time, this will have to do for today...