From: Christina Z. Anderson (zphoto@montana.net)
Date: 10/03/01-07:11:29 PM Z
Well, today I taught 28 students how to mordancage. Jonathan Bailey, I
commend you for doing so on a regular basis. I found it was certainly a lot
of cleanup, mixing, messing, etc. on my part but boy did the students have
fun! They looked pained when I told them I was gonna force them to do it
(like having to eat your green vegetables) but once started, they were at it
the whole time and all were happy I taught them the process--even the
perfectionist of the group!
I wanted to report back to the list that copper sulfate does absolutely
NOT work in the process. Luckily I had the copper chloride solution mixed
and enough to tide me over with 2 sections of lab, but I had mixed the same
formula, substituting copper sulfate at the same strength of copper chloride
(30g) with the acetic acid 80 ml and the water 1000 ml and the hydrogen
peroxide 40 v at equal parts, and no go. I ran over to the chemistry dept
and asked them what up wit dat and (aside from looking at me as if I were an
alien) he didn't seem to think they could interchange, but if so, it may be
that I should double the copper sulfate because there are 2 molecules
available with the copper chloride, etc. Then I doubled the copper sulfate.
No go. Then I quadrupled the copper sulfate and still no go. Thus, I don't
think I am wrong in concluding that in mordancage, it does not work. Neither
in bleach etch, being similar. They seem to only have in common the pretty
blue color and the smell. With the copper chloride, the reaction in the
bleach is quick. With copper sulfate, there is no reaction. So trust me,
this does not work.
However, my question is this: copper sulfate IS used in the bromoil
process: the bromoil tanning bleach is 70ml of 10% copper sulfate, 70 ml of
10% potassium bromide, and 30 ml of 1% potassium dichromate solution mixed
with 830ml water. This completely bleaches and tans 10 8x10's. Thus, I am
deducing from this that copper sulfate in combination with glacial acetic
acid and hydrogen peroxide does not work, but there must be something in the
bromoil formula that it *does* work in combination with. Else why would it
be in the bromoil formula? Any comments from the chemists of the group? Of
course, from now on I will only stick with copper chloride for mordancage,
and buy it from Tri-Ess as Jonathan recommends.
Chris
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