Routing silver-bearing waste

Purpose

To keep every gram of silver a session produces in one labelled container, and out of the drain. The arithmetic that makes this worth a procedure of its own is on the waste lesson: a ratio of about a thousand between what a spent fixer carries and what a sewer limit allows.

When to use it

Every session in which silver is dissolved, coated, fixed or washed. That is Part I’s photograms, Part IV, all of Part V, every printing-out process later, and every ordinary film or print session, because fixing is where the silver leaves the emulsion.

Before you start

You should already have read waste, silver and the drain, the silver nitrate lesson and the disposal caveat, and looked up what your own authority accepts.

On the bench: one rigid container with a sealing cap, labelled in advance and standing in a tray — beside the sink, not in a cupboard. The stream people lose is rinse water, and they lose it because it looks like water and the container was in the other room.

!This stream is one-way

A liquid moves into the silver-bearing container and never out of it into another stream. If you are unsure whether something carries silver, it does. The cost of being wrong in that direction is a slightly larger volume to store; the cost of being wrong in the other direction cannot be undone.

Procedure

1. Before the session starts, stand the container where you will be able to reach it from the sink with a full vessel in your hand.
2. Pour spent fixer into it.
3. Pour the first change of wash water after fixing into it as well. That change carries most of the thiosulfate and the silver out of the tank; the later changes are the ones whose route is a local question.
4. Add every rinse off a vessel, rod, brush, funnel or gloved hand that has touched silver nitrate, a sensitiser, an emulsion or a fixer.
5. Add any solution that has gone cloudy, grey or brown. It is no longer what its label says, so it is waste rather than stock.
6. Add any emulsion, sensitiser or coating that never became a picture, together with the water used to rinse the coating tools.
7. Put silver-bearing solids into a sealed, labelled bag — filter papers, wipes, loaded absorbent, used gloves, coating scraped off a plate. Not into an open bin: dried silver nitrate in paper is an oxidiser in cellulose.
8. Leave headspace, cap the container, wipe its outside and stand it back in its tray.
9. Top up the running-volume line on the label and add the date.
10. When it is full, close it, date it, and take it by the route you checked and dated. Not to a drain, and not to a septic system.
11. Write the log line.

How you know it worked

• The container stood within reach of the sink for the whole session and went back to its tray at the end.
• Nothing silver-bearing entered the sink, including the rinses that looked like water.
• Nothing silver-bearing was left to dry — no residue in a dish, no wipe in an open bin.
• The label carries a current volume, the route, and the date you last checked that route.
• The log records which process the silver came from, not only how much there was.

If a step fails

Step 3, the first wash has already gone down the drain. Record it, with your estimate of the volume, and move the container before the next session. The entry is what changes the habit; the container’s position is what makes the habit possible.

Step 4, you are not sure whether a rinse carries silver. It does. See the note above: this stream only ever gains.

Step 5, a solution has clouded and you would rather rescue it. It cannot be rescued. Silver has left the solution and the amount is unknown, so no addition corrects the strength — and the precipitate is itself light-sensitive.

Step 7, a loaded wipe has gone into an open bin. Retrieve it into the sealed bag. This is the domestic fire hazard the silver nitrate lesson names, and it is the one that looks like nothing.

Step 10, your authority does not accept it. The container stays sealed, labelled and in its tray while you find one that does; a sealed labelled container is a solved problem for weeks. Acceptance genuinely varies between neighbouring authorities, which is why the disposal caveat gives you a checklist rather than an instruction.

The container is nearly full and there is more to pour. Close it, date it, start another. Do not decant it into an unlabelled bottle to make room; that converts a recoverable, identified waste into an unknown.

What to record

The waste-log line: date opened, stream, container and size, date closed, running volume, route and the date you checked it. Then one column the general waste log does not need — which process the silver came from. That is the number Part XII will ask you for when it asks whether recovery at your own volume is worth the equipment, and nobody can answer it from a manufacturer’s average.