question about tartaric acid
S_IZZO@guvax.acc.georgetown.edu
Thu, 02 Feb 1995 17:13:29 -0500 (EST)
I have just joined the group. So far my only experience with
alternative processes has been with cyanotypes. I have spent the
last month learning and experimenting and generally having a good
time with this process.
I would like to try the Van Dyke process next and have a question
for the group. The sensitizing formula which I want to use calls for:
silver nitrate, ferric ammonium citrate, and tartaric acid. I have
the first two but not the tartaric acid. I understand the contribution
of the first two to the chemical reaction which forms the image, but
what is the contribution of the tartaric acid? An old photographic
chemical dictionary says it is used "as a preservative for sensitized
paper and in emulsions." Obviously here it is being used in an
emulsion; is it needed to preserve the image? Does anyone have any
experience using the formula without the tartaric acid? Since tartaric
acid is obtained from potassium hydrogen tartrate (cream of tartar),
I am also wondering whether it might be possible to use this as a
substitute. I also have some old baking powder which actually
contains tartaric acid in addition to cream of tartar, and I could
use that although I would have no idea of the amount. Another idea
would be to substitute another organic acid such as acetic, citric,
or oxalic. Any help will be appreciated.