Closing the laboratory

Purpose

To leave nothing behind that the next person — or the next you — has to work out. Every waste stream routed and sealed, every vessel clean enough to be trusted for its own family, every surface wiped, and the session written down while it is still in front of you.

When to use it

At the end of every session in which a container was opened, including the one that was cut short. An interrupted session is closed properly and then abandoned; it is never left standing.

If you must leave the room mid-session, cap everything open, put the trays inside their containment and take your gloves off first. A capped bench is a paused session; an uncapped one is an incident waiting for somebody who does not know what is on it.

Before you start

You should already have read the layout lesson’s pack-down sequence, the glove-removal sequence on protecting yourself, which is written out as donning and removing protective equipment, and the stream scheme on waste, silver and the drain.

On the bench: the waste container for each stream, a funnel per family, detergent and a brush, a damp cloth, the notebook.

Procedure

1. Stop work at the wet end and cap every open container, the empty ones included.
2. Pour each spent solution into the container for its own stream, through that family’s funnel, and top up the running-volume line on the label. Streams are never combined — see routing general chemical waste and routing silver-bearing waste.
3. Seal each waste container, wipe its outside, and stand it back in its tray where it lives.
4. Wash the vessels in family order, cleanest first: water-only, then developer, then stop, then fixer, then anything silver-bearing. Wash rather than rinse — detergent and a brush, then a rinse in clean water.
5. Collect the first rinse off anything that held fixer or silver into the silver-bearing container. It is dilute fixer, not water.
6. Invert everything to drain, and dry it before it goes away.
7. Wipe the bench, the tray and the splash guard with a damp cloth. A powder spill is cleaned wet; a dry brush puts the whole of it back into the air.
8. Wash the sink and flush the drain with cold water. Acid solutions attack a sink and its drainage, and the flush is what stops that being a slow surprise.
9. Rinse your gloves while you are still wearing them. Peel the first inside out and hold it in the gloved hand; get a bare finger inside the cuff of the second and peel it down over the first; drop the pair into the waste; wash your hands.
10. Put the dry end away: balance wiped and boxed with its calibration mass, thermometer in its case, data sheets back in the folder.
11. Return the room. Nothing on the surfaces, window shut, extract off.
12. Write the notebook entry now, at the bench, not tomorrow.

How you know it worked

• Nothing on the bench is open, and nothing on the bench is unlabelled.
• Every waste container carries a cap, a fresh running-volume figure and today’s date.
• Nothing that held fixer or silver was rinsed to the drain.
• The bench is dry, the sink has been flushed, and the gloves are in the waste rather than beside it.
• The notebook entry exists, and it names what you made, what you saw and what surprised you.

If a step fails

Step 2, a liquid whose stream you cannot identify. It goes into none of them. Put it in a fresh container labelled with the date, the session and unidentified, stand it in the tray, and settle it before it moves anywhere. Pouring an unknown into a labelled stream destroys the label’s meaning for everything already in the bottle.

Step 2, the container for a stream is full. Close and date it, and start a new one. Do not decant into whichever bottle has room; a mixed container has the disposal constraints of the worst of its contents and the value of none of them.

Step 4, a vessel still smells of fixer after washing. It is a fixer vessel from now on. Write FIX on it and replace it in the family it used to serve. Even a trace of fixer damages a developer, and no source in this course’s corpus publishes the amount that does not — which is why the working rule is exclusion rather than a threshold.

Step 5, the rinse has already gone down the drain. Write it down, with your estimate of the volume. That entry is the one that changes the habit; a rinse you did not record is a rinse you will repeat.

Step 9, a glove tears as it comes off. Wash the skin at once and at length. If what was in the glove was corrosive, treat it as a skin exposure and follow the first aid quick reference rather than waiting to see how it develops.

Step 12, you are too tired to write it up. Write three lines: what you made, how much waste went where, and what surprised you. Three lines tonight are worth more than a full page that never gets written.

What to record

The session line: date, what you made or processed, the quantities, and the observations. Then the volume added to each waste container, taken from the labels rather than from memory; any instrument check you ran; anything you retired and why; and any spill or exposure, however small and however embarrassing. The last of those is the entry the course most wants you to have a year from now.