Preparing and coating albumen paper

Purpose

To make a batch of salted albumen and turn it into flat, even, dry coated sheets that can be sensitised weeks later.

When to use it

Twice: on the day the batch is made, and again a week later on the day the paper is floated. Nothing here is light-sensitive — the coated sheet does not become so until it meets the silver — so both run in ordinary room light with the window open. Sensitising, printing and toning are a different session at a different level, under the coating bench sheet and the printing-out line.

Before you start

You should already know what the resting day and the refrigerated week do to the protein, from the binder lesson.

Level A, and its real control is hygiene rather than chemistry. Several dozen raw eggs are broken on a bench, and no egg can be guaranteed free from Salmonella whatever its source: hands washed and dried before and after, surfaces and equipment cleaned and disinfected afterwards, cracked or dirty eggs rejected, and no vessel that has held photographic albumen used again for food.

Two operations take goggles rather than spectacles: dissolving the ammonium chloride, which carries a serious-eye-irritation statement, and measuring the glacial acetic acid, signal word Danger for skin burns and eye damage. Both bottles are capped before the albumen is touched.

Ventilation is a control for one substance only, the 70 per cent isopropanol of the hardening route: a window or extractor running while its tray is open, no ignition source in the room, the tray covered between sheets.

On the bench: two bowls and a separator; a graduate, a syringe, the balance; a mixer; muslin; a covered labelled container for the refrigerator; a plastic-lined bench cover, because albumen sets hard and may harm a painted surface; nitrile gloves, which here protect the sheet as much as you.

Procedure

The batch

1. Label the container first — batch number, date, chloride and its concentration, acid, egg count — by the labelling procedure and the batch record.
2. Wash and dry your hands, and again each time you come back to the eggs.
3. Separate every egg over the small bowl and pour each clean white into the large one. Reject any egg that is cracked, damaged or dirty before breaking it; if a yolk breaks, that white is discarded.
4. Measure the white you have, and work to that volume rather than to the egg count.
5. Dissolve the chloride and the acid in a minimum of water, goggles and gloves on, acid into water and never the reverse, and cap both bottles.
6. Add the salt-and-acid solution to the whites and beat until the entire mixture has become froth. You are looking for complete conversion, not a timer.
7. Cover and let it settle for twenty-four hours: the froth liquefies and drains, and the chalazae and membranes stay up in it.
8. Strain the liquid from beneath the froth through muslin, squeezing if necessary, and discard the foam.
9. Cover, label and refrigerate for a week. Then look at it and smell it before you use it.

The coating day

10. Bring the albumen and the paper to the temperature of the room and give them an hour to get there.
11. Filter again immediately before use and pour into the tray to the specified depth.
12. Stir the surfactant in gently without raising bubbles, and record the figure you used.
13. Sweep the surface clear of bubbles with a strip of heavy paper drawn slowly to the side of the tray — before every sheet, not once at the start.
14. Float the sheet by two opposite corners, letting the centre touch first and lowering the corners away from you so no air rolls under.
15. Lift the sheet by one corner, inspect its underside for bubbles, break any you find and lay it back down. On a thick paper this is the only way to see them.
16. Start the clock when the sheet lies flat and every bubble is gone, not when it touched the liquid, and float for the published time.
17. Draw the sheet off slowly, one corner first. Lifted properly, hardly a drop leaves it while it drains over the tray.
18. Hang it by two corners of the long edge on a slightly inclined line, with a blotter beneath the low corner.
19. Blot the runoff several times while it dries. A dried rind makes the sheet very hard to work with afterwards, and the last droplet takes a very long time to dry.
20. Dry completely, drip corner included, then pile and flatten the sheets under weights.
21. If you are double coating: harden the first coat by the alcohol or the heat route, record which, mark the edge that hung lowest, and hang the second coat with that edge at the top so the two gravity gradients cancel.
22. Inspect every finished sheet in raking light before it goes in the box.
23. Bottle and label the used alcohol, and route the spent albumen and the rinses to the dilute-organic stream. Check your local regulations, which govern the routes.

How you know it worked

• No yolk, blood or chalaza reached the batch, and the bench was cleaned and disinfected afterwards.
• The whole mixture became froth, and the liquid drawn from beneath it a day later was clear.
• Every sheet was floated bubble-free, and the clock started when it lay flat.
• Nothing dried with a rind on it, and every drip corner is dry.
• On a double-coated sheet the two coats hung from opposite edges, and the fact is written down.
• The container carries batch number, date, chloride, acid and egg count.

If a step fails

Step 3, a yolk breaks into the large bowl. The batch is contaminated. Start again rather than strain it: yolk is fat and it will print.

Step 6, the froth stops building early. The chloride reduces the volume of froth. Judge by whether the mixture has all converted, not by its height.

Step 9, the batch smells strongly wrong rather than slightly aged. Discard it. The end point is sensory and the threshold is low.

Step 14, air has rolled under the sheet. Lift it, break the bubbles, lay it back and restart the clock. Bubbles show through a thin sheet as light circles on a dark ground and not at all through a thick one.

Step 17, a flood of albumen comes off the sheet. It was lifted too fast and albumen has gone onto the back. Blot it, mark the sheet, and expect it to differ from the batch.

Step 19, a rind has dried at the low corner. Keep the sheet as a reference of the fault rather than sensitising it: it will not lie flat in a frame.

Step 21, the press or iron marks the sheet. Stop and record the setting: a marked sheet is a worse outcome than an unhardened one.

What to record

The batch: number, date, egg count and volume of white, chloride and its concentration, acid, beating and resting times, straining, and the date it was refrigerated, with its appearance and smell when it came out. The coating: room temperature and humidity, surfactant figure, float time, drying time and method, single or double coat, the hardening route if any, and which edge hung low on each coat.