How to dry film without water spots or dust

To dry film without water spots, give it a final rinse in distilled or deionised water with a wetting agent, at the dilution on its data sheet: 1+200 for both Ilford Ilfotol and Kodak Photo-Flo 200. Then hang it straight away in a still, dust-free place, with a weighted clip at the bottom, and do not touch it until it is dry. Water spots are the minerals that tap water leaves behind when a drop dries on the film, and the rinse stops those drops from forming.

What you need

• A wetting agent: Ilford Ilfotol, Kodak Photo-Flo 200, or the final rinse that comes with your colour kit.
• Distilled or deionised water for the final rinse. Both have the minerals removed, so either works.
• A small syringe or pipette to measure the wetting agent. At 1+200 you need only a few millilitres.
• Two clips per strip, one of them weighted.
• A place to hang the film where the air is still and clean, or a drying cabinet.
• A tray or dish to catch drips.
• Optional: a film squeegee or a chamois, kept spotless.

Why water spots happen

Plain water clings to film in drops. Each drop dries where it sits and leaves a ring of whatever was dissolved in it: calcium, magnesium and other minerals in hard water, or traces of processing chemicals. On a scan, the rings show up as small round marks, often with a darker edge.

A wetting agent lowers the surface tension of the water, so it runs off the film in a thin, even sheet instead of forming drops. Kodak describes Photo-Flo exactly this way: it lowers the surface tension of the water and so reduces water marks and speeds drying. Distilled water removes the minerals, so any drop that does form leaves nothing behind. Together they stop almost all spots.

Mix and use the final rinse

1. Finish the wash as usual, in tap water.
2. Fill the tank with distilled or deionised water at about the same temperature as the wash. Kodak gives 18 to 21 °C for Photo-Flo.
3. Add the wetting agent. Ilford recommends starting with 5 ml of Ilfotol per litre of water, which is 1+200. For a 300 ml tank, that is 1.5 ml, so use a syringe or a pipette. Kodak gives the same 1+200 dilution for Photo-Flo 200.
4. Stir gently. Do not shake the tank: Ilford warns that wetting agent foams with too much agitation, and foam can leave marks.
5. Leave the film in for about 30 seconds, Kodak’s time for Photo-Flo. Then lift the reel out. Do not rinse the film again.

Measure the wetting agent carefully. Ilford notes that too little and too much both lead to uneven drying, and that the right amount depends on your water and your drying method, so you may need to adjust it slightly. If you still see streaks at 1+200, try a little less before you try more.

Ilford gives a life of 7 working days for diluted Ilfotol, so mix a small batch, or mix it fresh each time.

For colour film, use the final rinse or stabiliser from your kit, mixed with distilled water if your tap water is hard. The Kodak C-41 kit lists hard water in the final bath as the cause of drying spots, and suggests mixing tap water with distilled or demineralised water.

Squeegee or not

A squeegee or a chamois takes the last water off the film before you hang it. Harman recommends a clean squeegee or chamois cloth to avoid drying marks, and Ilford’s beginner guide uses squeegee tongs.

The risk is grit. Ilford’s own warning: any grit caught in the squeegee will scratch the whole length of the film. A water spot can be washed off. A scratch is permanent.

Your options:

• Squeegee, if you keep it spotless: rinse it before every use, wet it in the same final rinse, and pull it down the film slowly, in one pass.
• No squeegee. With the right dilution and distilled water, the rinse drains off on its own. Touch the bottom corner of the strip with a lint-free tissue to wick away the last drop.
• Fingers. Some people run the film between two clean, wet, gloved fingers. It is gentler than a dirty squeegee, but the same rule applies: anything on your gloves ends up on the film.

How I do it. I squeegee my film, then hang it to dry from the clothes hanger in my bathroom.

Hang the film

• Hang it straight away, clipped at the top, with a weighted clip at the bottom. The weight keeps the strip straight and reduces curl. If your film still curls, see flatten curly film.
• Hang it high enough. A 36-exposure roll of 35mm is about 1.4 m long. Ilford suggests a line about 2 m off the ground.
• Put a tray under it to catch drips.
• Keep the air still. No fans, no open windows, and nobody walking past. Close the door.
• Leave space between strips so they cannot swing into each other.
• Do not touch it until it is completely dry. The emulsion is soft while wet, and a fingerprint or a hair stays in it.

Ilford mentions that you can speed up drying with a hair dryer on a low setting, kept moving, about 30 cm from the shiny side of the film. A hair dryer also blows dust around, so use it in a clean room or not at all.

Sheet film dries the same way: clip one corner to a line, or stand the sheets in a drying rack, emulsion facing out, so they do not touch.

A drying cabinet

A drying cabinet is a closed, upright box with a fan and a heater that pushes warm air through a filter. It dries film faster and keeps dust off. Use the temperature your film’s data sheet or your kit allows:

• Harman, in its Kentmere Monobath data sheet: 30 to 40 °C in a drying cabinet, or room temperature in a clean, dust-free area.
• Kodak C-41 kit: 24 to 43 °C.
• Kodak E-6 kit: up to 60 °C.

Without a cabinet, any closed space with still air works: a tall cupboard you keep clean, or a shower cubicle. Some people run a hot shower for a minute first, so the steam settles dust out of the air. The humid air slows drying, so give the film longer.

Keep dust off

Most dust on a scan lands on the film while it is wet. To keep it off:

• Wipe the drying area with a damp cloth before you hang the film. Do not sweep or vacuum just before: it lifts dust into the air.
• Wear clean clothes without loose fibres when you handle wet film.
• Wait until the film is fully dry before you cut it, and put the strips into sleeves straight away. Hold them by the edges only.

When dust has already landed, dust on film scans covers how to clean the film and how to remove what is left from the scan.

Rewash spotted film

If you find water spots on dry film, you can rewash it:

1. Load the film back onto a reel, or lay the strips in a clean tray.
2. Soak them for a few minutes in clean water at about the processing temperature.
3. Repeat the final rinse in distilled water with the wetting agent. For C-41 film, repeat your kit’s final rinse or stabiliser instead.
4. Hang the film and let it dry again.

Do not try to rub dry spots off with a cloth. On the emulsion side, that risks scratches that are worse than the spots.

Common problems

• Small round marks with a ring. Hard water dried on the film. Use distilled or deionised water for the final rinse, and rewash the film.
• Streaks or uneven drying marks. Too much or too little wetting agent, or foam. Measure the dilution and stir gently.
• Fine straight scratches along the whole roll. Grit in the squeegee or chamois. Clean it or stop using it.
• Hairs and dust stuck in the emulsion. Dust settled while the film was wet. Dry it in still air or in a cabinet.
• Strong curl. No weighted clip at the bottom. Add one next time, and flatten the dry strips before you scan.

Sources

• Ilford: Sundry chemicals fact sheet, with Ilfotol (copy hosted by Maco)
• Kodak Alaris: Chemicals for Kodak Professional black-and-white films (E-103CF)
• Ilford: Processing your first black and white film (copy hosted by the University of Wisconsin)
• Harman: Kentmere Monobath Film Developer data sheet, F26 (PDF)
• Kodak: C-41 film processing kit instructions (PDF)
• Kodak: Color Reversal E-6 slide processing kit user manual (PDF)