Mike Ware says the response he's received about the new cyanotype has one
common concern: its relative toxicity. I thought I'd post his words so
everyone can see it. I'm sure he'd do it himself, except he's not a
member of the list. Here it is:
Potassium ferricyanide is, of course, also an ingredient in the
'traditional cyanotype' process. The Materials Safety Data Sheet rates it
as a low toxic hazard: 1, on a scale of 0 (harmless) to 4 (extreme).
My new cyanotype process is more poisonous than the traditional version,
because instead of citrate it involves oxalate; some oxalates rate 3, on a
hazard scale of 0 to 4. (They're also present in rhubarb leaves, spinach
and sorrell!)
I have not been able to find a Materials Safety Data Sheet for ammonium
ferric oxalate, but it should be treated as probably rating 2-3. Its toxic
hazard must be similar to that of ferric oxalate, which is widely used by
people practising Kallitype and Platinum-palladium printing, as you know.
This is what I say about it in my Web pages:
Ammonium iron(III) oxalate. Like all soluble oxalates, this is
classified as highly toxic, i.e. capable of causing death or permanent
injury (especially kidney damage) if taken by mouth. However, several
grams
would have to be ingested to cause this. The chemical takes the form of
large, non-volatile crystals, highly soluble in water, so there is little
risk of inhalation, but it is an irritant to skin, eyes and mucous
membranes.
Disposed of down the drain in small amounts, diluted with water, it cannot
do harm in the environment or to the waste disposal system and will
speedily be decomposed. (I can't answer for any local regulations tho').
Ammonium dichromate is a listed human carcinogen, hazard rating 4
(extreme)
in the MSDS and best avoided, if possible. (However, this doesn't inhibit
the Gum Bichromate printers!)
There is only a small amount in my recipe, but one could try leaving it
out
altogether, it's only there to assist keeping and remove ferrous iron
impurities which would form Prussian blue.
Hope this helps.
John
John Barnier
12560 Morris Trail North
Marine on St. Croix, Minnesota 55047
USA
jb@dgi.net
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