Refrigerated emulsion labelling and food separation

Purpose

To put an emulsion into cold store labelled well enough that whoever finds it can say what it is, how old it is and the day it stops being usable — and to keep the cold store and the household’s food apart.

When to use it

Every time emulsion leaves the bench for a refrigerator, at any of the three stages a make produces: unwashed emulsion set before the wash, washed noodles held between the wash and the ripening, or a finished emulsion held between coating sessions. It also runs once, in full, when you commission the refrigerator.

Not for coated sheets, which are dry and go in a lightproof box, or for unmade silver nitrate, which its own procedure governs and which never shares this box.

Before you start

You should already know why an emulsion is perishable and why the keeping times differ by stage, from gelatin, the photographic binder and the Keeping section of coating, drying and hardening.

This is Level A work: nothing weighed, heated or dissolved, no silver nitrate opened, the material handled set, sealed and cold. Nitrile gloves, because it is silver-bearing, and safelight or darkness whenever a container is open. Remelting or coating it puts you back in the emulsion session at Level B.

On the bench: a refrigerator with a thermometer in it; a rigid, closable lightproof box that fits its lowest shelf, standing in a tray; sealable bags or wide-mouthed jars; labels and a waterproof pen; the batch record from recording a batch.

!Where the separation rule comes from

The manufacturers are unanimous. ILFORD: keep foodstuffs away from where photographic chemistry is prepared and stored, and keep it out of reach of children and animals. Kodak: a designated area, away from food. What is in this box is classified on the silver bromide page, caveats and all.

Procedure

The refrigerator, once

1. Decide the cold store before you make anything. A refrigerator used for nothing else is the answer; where the only one available also holds food, everything photographic lives inside one closed box.
2. Stand that box in a tray on the lowest shelf, below every shelf holding anything edible and never above one, as storage rotation requires. A leak goes downwards.
3. Label the box outside, and the door it lives behind, before anything goes in: EMULSION — SILVER — NOT FOOD, your initials and the date.
4. Put a thermometer inside and read it before the first batch. Part V’s keeping figures assume a refrigerator, and the several-month figure is stated for below 5 °C.
5. Keep everything out of the freezer and off the ice shelf. Washed noodles are never frozen.
6. Use bags, jars and boxes bought and marked for this. None has held anything edible and none goes back to a kitchen — Part II’s rule for every vessel.

Every container that goes in

7. Write the label before you fill the container, by labelling a container. These fields are the ones it does not carry.
8. Batch code and date made, the same code as the batch record line.
9. Stage, in one word: UNWASHED, NOODLES or FINISHED. It sets the use-by date, and it is the field people leave off.
10. Date and time it went in.
11. A use-by date — a day, not a range. Unwashed and undigested keeps a few hours to a few days, and up to a week for the chloride paper emulsion; washed noodles keep several days; a finished, digested emulsion below 5 °C keeps several months. Take the short end and write the day.
12. A remelt row, one box ticked per melt. No source read gives a maximum, so an uncounted batch cannot be diagnosed later.
13. Volume, and the words SILVER and NOT FOOD.
14. Fill the bag or jar as full as you can, exclude the air, seal it before it is chilled.
15. Put the sealed container inside the closed box, the box back in its tray, and the line in the batch record.

Taking it out again

16. Read the label before you open the lid: stage, use-by date, remelt count.
17. Tick the remelt box as you melt it, not after.
18. Past its use-by date it is retired rather than judged by eye, and goes to silver-bearing waste under the disposal caveat.

How you know it worked

• Anybody opening the refrigerator sees one closed, labelled box and nothing loose on a shelf.
• Nothing edible sits below that box, and nothing photographic above anything edible.
• Every container inside carries a batch code, a stage, a date in, a use-by date and a remelt count.
• The thermometer reads below 5 °C, and nothing has been frozen.
• Every container in the box has a line in the batch record, and every line has a container.

If a step fails

Step 1, the only refrigerator holds food and the bottom shelf is full. Then there is no cold store, and the make is what changes: halve the batch and coat it out in the session, or clear the shelf first. A shelf shared by stacking is not separation.

Step 4, the thermometer reads above 5 °C. The several-month figure is stated for below 5 °C and does not apply. Write a use-by date in days, and the measured temperature beside it.

Step 9, you cannot say which stage the emulsion is at. Then it has no keeping time. Give it the shortest on the list and use it today, or retire it.

Step 11, the make is a variant nobody has published a keeping time for. Take the shortest figure for its stage and make your own evidence: keep two sheets from the batch in the dark, and develop one unexposed before you commit a picture to it. No rate of keeping fog has been published for hand-coated material, which coating, drying and hardening says in as many words.

Step 12, the remelt count is missing. Write unknown in the row and count from this melt. A remelt nobody counted is the first thing to suspect when a batch later coats thin.

Step 14, the container will not fill without leaving air. Use a smaller one.

Step 15, you find something edible inside the box, or the box standing above food. Contamination runs both ways: discard the food, empty and wash the box, re-site it. Sealed, intact containers go back; an opened one is retired.

A container has leaked inside the refrigerator. It is a silver-bearing spill in a space where food is kept. Glove up, empty the shelf, collect it rather than rinsing it away by silver-bearing waste, discard anything edible it reached, wash the shelf. Spill response governs the clean-up.

Step 16, the label is missing or unreadable. It is an unlabelled container, whatever you believe is in it. Do not melt it to find out.

What to record

Against the batch record line for that code: the stage it went in at, the date and time in, the volume, the measured temperature of the store, the use-by date and which figure you took it from, and a dated tick for every melt. Then the date it came out and what became of it — coated, held again, or retired to the silver stream. The shelf life of your own emulsion in your own refrigerator is a number nobody has published; those lines are how you get it.