[Alt-photo] Dichromates and Septic System?

Diana Bloomfield dlhbloomfield at gmail.com
Thu Feb 15 15:41:14 UTC 2018

Thank you!!  Very helpful.

On Feb 15, 2018 10:30 AM, "Richard Sullivan" <sullivan8486 at gmail.com> wrote:

>From Bostick & Sullivan C. 2002Gum Dichromate Green

Types of chromium

Gum printing involves the use of hexavalent chromium. This form of chromium
has achieved a bit of notoriety since the release of the movie Erin
Brockovich. Yes this is the same form of chromium that Ms. Brockovich was
dealing with in the film.

Some caveats: It is dangerous and can be carcinogenic. However, remember
the Borckovich film was dealing with industrial usage levels. The film was
dealing with tons and tons being willy nilly dumped into the local soil and
going into the water supply. Pretty scary. We are dealing with grams.

First, let me say that some of the data and information being passed on
around on gum printing is based on industrial exposures levels of chromium
compounds. In days gone by men would roll up their sleeves and dunk hides
into vats of the solution for tanning and do this all day long or they
would work in chrome plating shops where it was not uncommon to roll up one
sleeve and reach down in a vat of it  to fetch a piece which had fallen to
the bottom. These men's arms would literally turn orange which they washed
off with some bisulfite. This does not happen today in most places though
I'd not be surprised to know that in some developing countries it is still
being done this way. It is a good idea to have an MSDS sheet handy, your
seller should provide one. In reality, MSDS sheets are always worst case
condition. If you read a number of them you will see that they are almost
all the same and are based on a formula. For instance it lessens any
liability and most say that for any skin contact you should seek medical
aid immediately after flushing with water. Because of this I think they in
effect are causing more harm then good as people become accustomed to
thinking everything is dangerous and will develop a "Oh what the hell"

Ok, you don't want to give up gum printing and you want to be a good
environmental citizen so what do you do? With gum printing we are not going
to dealing in these extremes. Hexavalent chromium can however be dangerous,
no doubt about it, but it can be dealt with safely.

First off let's deal with our personal safety. Gloves are essential. Of
course follow common sense rules. Always keep solutions in well marked
containers, never store in anything looking like a food container and NEVER
store near food or in a refrigerator.


This issue is in my mind the most dangerous aspect of gum printing chromium

A paper face mask is needed for weighing and mixing the dry crystals. If
drying the coated paper with a hair drier or fan a face mask would be a
good idea. During development a mask is not needed as the compound will not
become breathable when in solution but gloves are essential. It is not
volatile like acetone, or gasoline.

 Incidental contact should be avoided but small splashes on the hands arms
or face only need to be rinsed off thoroughly and do not require a visit to
the emergency room.

Never ever mix with any compound unless you specifically know it is safe to
do so. The chromium compounds are powerful oxidizers and with combination
with a fuel source can cause fire or explosion. The Oklahoma Bombing was
done by combining a fuel source Diesel fuel with an  a common fertilizer
(an oxidizer.)   Do not combine with any powdered metals like aluminum or
iron. Do not combine with any hydrocarbon or volatile fuel compound. Do not
combine with glycerin.

The gum printing chromium compounds  are safe when stored properly.

Collecting the nasty stuff

This step is particularly important if you are on a well and a septic
system! That is not to say you should be dumping it into your municipal
system however.

The first step is to collect your gum developing run off. You may wish to
collect this in a large tank or plastic garbage can.
Converting to trivalent

Add sodium bisulfite, sodium sulfite, plain old spent fix or sodium
thiosulfate to the solution. The solution will turn from orange to green.
Keep adding until there is no more green color and add a bunch more to
insure all is converted.  It is now a much safer trivalent chromium
Making a precipitate of the chromium

You want to go a step further. Now add an alkali to the solution in the
tank or garbage can. You can use sodium hydroxide (plain old Draino works
fine.) or sodium carbonate or potassium carbonate. After the alkali is
added  the chromium now is converted to chromium hydroxide which can be
filtered out.
Building the filter thingy.

I have not attempted the filtering step on a large scale as I have not gum
printed in several decades. I have however filtered tanks of solution many
times before with this system. Here's how I would approach the problem:

I'd start with a small pond pump. Not a real tiny one but one that costs
about $50.00 would be large enough to handle a 50 gallon plastic garbage
can. Now buy a house size water filter. They are available in nay hardware
store and are usually blue plastic and are about the size of a 1 liter
Pepsi Bottle and cost about $15.00. Next buy the fittings necessary to
attach the blue plastic house water line filter to the outlet of the pond
pump directly. Install a cheap paper filter into the housing ($3.00 -
$5.00). Do not use the expensive charcoal filter cartridges as they are a
waste of money in this case.
Filtering the tank

Dunk the pond pump with the filter directly attached into the tank. Plug it
in and let it run overnight. It will intake and discharge into the tank.
This is less efficient than filtering from one tank to the next but the
plumbing is far simpler. I've used this system to filter stuff in tanks in
the past. You may have to change the filter 2 or three times depending on
the amount to filter out.
Disposing of the wet nasties

When finished put the filters  in a 1 gallon zip lock bag and label the
bags "Chromium Oxide Waste." Take the bag to your  hazardous waste disposal


On Thu, Feb 15, 2018 at 6:54 AM, David Robertson via Alt-photo-process-list
<alt-photo-process-list at lists.altphotolist.org> wrote:

> Adding a reducing agent like sodium sulphite (or bisulphite) would reduce
> the chromium to the 3+ oxidation state. Chromium (III) is much less toxic
> than chromium (VI). I always do this before disposing of any hexavalent
> chromium compounds.
> David
> > On 15 Feb 2018, at 13:46, Diana Bloomfield via Alt-photo-process-list <
> alt-photo-process-list at lists.altphotolist.org> wrote:
> >
> > I'm sure this question has been asked and answered before, but I can't
> > locate it.  A friend who wants to learn gum printing asked about what to
> do
> > if you have well water?  Does anyone know the answer?  I thought there
> was
> > something you could add to a septic system that neutralizes the
> dichromate
> > somehow??  Thanks!
> > _______________________________________________
> > Alt-photo-process-list | altphotolist.org
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