Re: alternative to dichromate sensitizer

On Tue, 18 Jan 2005, T. E. Andersen wrote:

> One of the things that bothers me most about old photo processes is the use
> of dichromate. Toxic, carcinogenic, environmentally harmful. All in all, not
> a nice ion to work with.

You may not have been here during earlier discussions of this topic... in
which I noted the following: Having been told by a chem lab assistant
that I would have to recycle every tray of wash water from my students'
gum prints, and fully aware that I could hardly get them to dump a tray
let alone recycle it, and that the school had no recycling program of any
kind in effect, if this prevailed I would stop teaching the medium. So I
called the EPA.

After a day on the phone I got to someone who either was in charge or
acted that way, a Captain, or maybe it was Lieutenant so & so, and
explained the problem to him. "How much dichromate do you use?", he
asked. After some reflection I figured that my students and I together
probably used about a pound a year.

He laughed. We're concerned with air conditioning systems that use a
pound every 45 minutes, he explained. Don't worry about it.

Nevertheless, I and others let the sediment settle to the bottom of a
"first wash" tray, and every so often collect it as solid waste. (It's
mostly pigment, BTW.)

That of course obtains in a city where 1000 toilets are flushed every
minute & the water flow is sufficient to dilute it and treatment at the
sewage plant chelates (or otherwise diminishes) passing chemicals.

Where a private house has a septic tank or other system, considerations
are different & need to be taken seperately -- but the dichromate used in
gum is VERY little, and diluted, also by the time it hits the water it's
reduced to -- what is it, trivalent???? form, which is not (so) toxic.
The mercury-containing juice from the can of tuna fish you drain into the
sink could be worse, maybe.

But this is, BTW, another reason I don't use full concentration
dichromate. So I may expose 4 minutes instead of one minute -- otherwise
the print is exactly the same, and I've used 75% less of the chemical.

As for toxic and carcinogenic:

1: If you're letting that stuff loose in the air or in crystals to float
around your studio -- you're already so stupid (nothing personal, just a
generalization) you may not suffer further injury.

You wipe the neck of bottles, wet-mop spills promptly, wear a mask when
mixing, don't shake the chemical onto the tray but spoon out carefully,
cover all trays, don't dry emulsion with a hair dryer, and so forth and so
forth and so on -- basic rules that should be followed ALWAYS with ALL
chemicals.

2. Um, which photo chemicals do you think are benign, besides maybe
sodium carbonate, and you don't want to breathe that either ?

3. Digital process has its own toxicities, in manufacture and use. I don't
know those myself, but I'd bet the inks & pigments aren't
environment-neutral. Practically nothing is, not even baby powder (but
that's a different rant).

Judy
Received on Tue Jan 18 16:53:36 2005