"jch" <jch@[EMAIL PROTECTED]
> wrote in message
news:ukxTj.244286$pM4.43310@[EMAIL PROTECTED]
> _____
> Hello All,
>
> I have been reading about divided developers for film.
> Never tried it; looks promising though! Do any of you in
> this group have any experience with this approach? The
> reason for my interest is the fact that i live in the
> country and that my house disposes of waste water via a
> septic tank system. Hence, i want to minimise the amounts
> of photographic chemicals entering the tank in case they
> kill the microbes.
>
> Below is a divided developer formula; a variant on D-76
> where BATH A and B can be kept for a long time:
> A BATH
> Water at 125F 3 cups
> Metol 1/2 tsp
> Sodium sulfite 2 TBL
> Hydroquinone 2 tsp
> Potassium bromide 1/8 tsp
> Cold water to make 1 quart
>
> B BATH
> Water at 80-100F 3 cups
> Sodium sulfite 2 TBL
> Borax 2 TBL
> Cold water to make 1 quart
>
> Process 2-4 minutes in A BATH, and the same time in B
> BATH, both at 68F. Agitate for 15 sec initially, and for
> about 5 seconds every half minute. Stop bath is not
> recommended after B BATH, a quick 1 min rinse in water is
> enough. Fix the film in the usual manner.
>
> A BATH will last indefinitely, and B BATH can be used for
> 20-30 rolls of film before any change in contrast or
> density should be noticed.
>
> There is also a phenidone version of this formula to
> obtain increased film speed.
>
> --
> Regards / JCH
Devided or two bath developers work on the principle
that the emulsion soaks up the developing agents from the
first bath and they are made active in the second. Since the
amount of developer that the emulsion can hold is limited
the amount of development is limited. In theory this can
result in a consistent contrast with limited control and,
for some films, for reduced development of the highlight
areas since, presumably, the developing agents get used up
faster there. In practice the system often does not work
very well especially with modern films which have much
thinner emulsions than those of the 1930's when most of
these developers were devised.
On your main point about polution: I think there will be
little difference between the single bath and two bath type
developers. To cut down on discarded developer it makes more
sense to use a replenished system. When the developer
eventually reaches the end of its life it can be disposed of
at a recycling place. This takes quite a bit of time so it
can be done even if you are out in the sticks.
The real culprit for septic tanks is hypo. Hypo
accumulates silver in a form which kills some types of
bacteria. The bacteria in the tank are what causes it to
break down the waste so you want them to be healthy.
Kodak used to have an on-line pamphlet about photo
chemicals and septic tanks, I don't know if its still there
but its worth a look.
Much of the silver in hypo can be recovered by simple
methods. For instance, the silver will plate out on steel
wool put into the solution. Use oil and soap free steel
wool. It takes several days and the resulting hypo can not
be reused but is environmentally friendlier.
There are a number of developers available with
replenishers or are self-repleni****ng. D-76, Xtol, and T-Max
RS are examples.
--
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@[EMAIL PROTECTED]
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