Re: blue in cuprotype answer
I don't belong to Hybrid so I can't access it. I'm really trying to hold
myself back from yet one more list, but if I can't view it otherwise then I
might just have to join.
Isn't experimenting fun??
Christina Z. Anderson
----- Original Message -----
From: "Bruce" <email@example.com>
Sent: Wednesday, January 21, 2009 12:11 AM
Subject: Re: blue in cuprotype answer
Thanks for your reply. It seems that the last paragraph may be the answer
to my problem. It describe exactly what is happening to my prints, so I
will try the citric acid. I just posted a print at hybridphoto so if you
get a minute take a look
Thanks and good luck with your other tests. Too many processes and not
On 20-Jan-09, at 6:40 PM, Christina Z. Anderson wrote:
Below is the kind and detailed answer I got form Jim Patterson, the
originator of the cuprotype process I posted on the list some while ago.
Maybe it will help with the problem of bluing out?
I am busy with chromoskedasic testing and gum so it'll be a cold day in
hell before I get to cuprotype so enjoy his notes and post some work
Christina Z. Anderson
Hi Chris, Good to hear from you. Here's some info that may help.
The first image formed in the developer is copper (1) thiocyanate, and
the citric acid in the developer is to help mobilize the iron out of the
paper. The clearing bath is diluted developer to have a small amount of
thiocyanate to keep the copper thiocyanate insoluble by common ion
effect, and the citric acid helps remove the iron. Adding more citric
acid to the clearing bath will help remove the iron better, but if it is
too high it may remove part of the copper thiocyanate image. I toyed
with the idea of making a separate clearing bath, which may be more
effective, with a small amount thiocyanate and more citric acid, but I
was trying to avoid more solutions and keep it simpler. Example:
Clearing Bath: 0.1 % ammonium thiocyanate and 1 % citric acid. If you
don't clear the iron salts out of the paper, when you add it to the
toner (potassium ferricyanide), any iron immediately reacts with the
ferricyanide to cause a permanent blue stain. Use distilled water for
the clearing bath to avoid iron in tap water.
The WASH of dilute acetic acid is to remove the ferricyande toner out of
the paper. If ferricyanide is not removed from the paper, it auto-
decomposes after some time to iron ferricyanide, the blue stain. If
your tap water has iron, use distilled water. Also a 1% citric acid
wash may work better than the acetic acid wash.