A container found unlabelled, or a solution of unknown age

Purpose

To deal with the fault a home darkroom produces more often than any other — a container whose contents cannot be stated — without opening it, without guessing, and without tidying it into somebody else’s stream.

When to use it

Two discoveries, sharing the first four steps and then parting company. No identity: a bottle marked DEV in marker pen, a jar with a supplier label half peeled off, a bottle with nothing on it at all. An identity with no age: a container that says what it is but not when it was made or first opened, or that carries one date on a bottle you know has been topped up.

Before you start

You should already have read why a date cannot be replaced by an inspection, on storage and incompatibilities, and the fields a label carries, on reading a safety data sheet. The diagnosis and the chemistry behind it are the atlas entry for an unlabelled or undated container.

On the bench: a tray, a marker that survives water, a blank label, the chemical inventory and the waste log. No glassware, because this procedure opens nothing.

!Step 1 is declared Level B inside a Level A procedure

The baseline is Level A and stays there, because nothing is opened, diluted or used. Moving a container whose contents you cannot state is declared Level B, since you can rule out neither a concentrate nor a corrosive. Its controls, stated here rather than left to be inferred: chemical splash goggles rather than safety glasses, gloves, both hands, carried at bench height and never above your face, moved once, set down in a tray.

Procedure

1. Put it down where it is, upright, inside a tray, with the goggles and gloves of the note above on. Move it once and no further than the nearest tray.
2. Do not open it. Do not smell it, taste anything, test a little of it in a developer or dissolve a pinch to see what happens. No bench test distinguishes a sound sulfite from an oxidised one, and each of those turns a labelling problem into an exposure.
3. Write on it now, in one word: UNIDENTIFIED, with today’s date and where you found it. That is not a label; it is a warning that stops the next person repeating your first two minutes.
4. Stop using anything that came out of it this session, and mark whatever it went into as suspect.
5. Decide which of the two problems you have. If nothing on the container states the substance, work through steps 6 to 10. If the substance is stated and only the age is missing, go to step 11.

Where the identity is missing

6. Write down whatever the container still says — a supplier’s remnant, a family abbreviation, a cap colour, an embossed volume — without interpreting it.
7. Look for a match in the inventory and the waste log: a purchase with no bottle, a batch line with no container. One line, one bottle, no ambiguity.
8. Where the match is certain, relabel it in full by labelling a container and record what made you sure. A relabelling you cannot explain in a sentence is not certain.
9. Where it is not certain, it is waste: it cannot be used, because you cannot state what it is; cannot be stored, because you cannot state what it must not stand beside; and cannot be described to anybody who might take it.
10. Stand it apart from the acids and from the silver nitrate while it waits, since you can rule out neither pairing, and label the tray as well as the bottle. Where it goes next is a local question the disposal caveat sets out how to answer; this procedure issues no disposal instruction.

Where only the age is missing

11. Ask whether it changes without showing it: sulfite oxidising to sulfate, a hydroxide carbonating, a deliquescent salt that has taken up water, an effloresced hydrate that has given it up. If it does, there is nothing to inspect and step 13 is the answer.
12. Apply the course’s criterion, which tests your willingness rather than the chemical: use it only if you would be willing to write in the notebook that you used it and why you judged it sound.
13. Where the answer is no, retire it, and write down what it was, roughly how old, what made you retire it and what replaced it. Ten such entries beat any published shelf life, because they measure your own storage.
14. Where the answer is yes, do not invent a mixing date. Write found and judged sound on with today’s date beside whatever the container already said, so the next person can see which part of the label is evidence and which is a judgement.
15. Fix the cause before you leave the bench. The label goes on before the container is filled: the minute you saved is the minute the telephone takes to ring.

How you know it worked

• The container was never opened.
• It carries the word UNIDENTIFIED, a date and a place, in writing that will survive being wet.
• The notebook says which of the two problems it was, and what you did.
• Nothing from it went into a labelled stream, and nothing labelled went into it.
• No date on it could be mistaken for a mixing date.
• The inventory or the waste log has gained a line, so the same bottle is not rediscovered next year.

If a step fails

Step 1, the container is cracked, crusted or leaking. That is a spill in progress rather than a labelling problem. Contain it in the tray and go to responding to a spill, which routes on by what it looks like.

Step 2, you have already opened it. Cap it, put it down, and record that you did. Nothing you saw while it was open is evidence: colour, smell and clarity distinguish almost none of the failures that matter.

Step 7, the inventory has no line for it. Then the inventory has failed too, and the container is waste under step 9. Start a line for every container you can still identify before you close the cupboard: the next unlabelled bottle is matched against that sheet or against nothing.

Step 8, two inventory lines both fit. That is not a match. Two candidates is one unknown wearing a plausible name, and step 9 is the honest outcome.

Step 10, you have several such containers. Do not consolidate them. Combining unknowns gives one larger unknown with the properties of the worst of them, and may combine a pair the incompatibility matrix forbids. One container, one label, one line.

Step 12, you want to double the quantity to allow for oxidation. That substitutes one unknown for another, and changes what the substance does in the formula as well as how much of it is there.

What to record

One line: what was found, where, on what date, and which of the two problems it presented. Then the outcome — relabelled and why you were sure, or retired and what replaced it. Finally the sentence that pays for the procedure: how it came to exist. The bottle filled before it was labelled, the decant that inherited nothing, the top-up that made a date untrue. A darkroom that keeps that list stops producing these.