Wet photographs: what to do in the first two days.

You have about 48 hours, and the clock is about mould.

Two things happen to wet photographs, on different timescales.

Physical damage happens immediately and is mostly caused by handling. A wet emulsion is soft. It will lift off its support if you peel a wet print from another wet print, wipe it, or try to separate photographs that have dried in contact with each other.

Mould starts at roughly 48 hours in warm conditions and slower in a cold room. Mould is the serious one: it feeds on the gelatine that holds the image, it stains permanently, and it spreads to every dry photograph you later store the wet ones beside. A collection that is dried properly within two days is usually recoverable. A collection left damp in a bin bag for a fortnight is not.

So the rule is not "dry them fast". It is get them dry, or get them cold, before mould has a chance to start — and never leave them stacked while you think about it.

Document, then stabilise. In that order.

1. Photograph the damage before you touch anything. Wide shots of the room or box as found, then close shots of the affected items. This matters for insurance, and it matters more for you: once a collection has been separated and dried, the evidence of what was there and how bad it was is gone. Ten minutes with a phone.
2. Stop anything in contact from staying in contact. Wet prints stacked on each other will block — the emulsion bonds to the print above it, and the block is not recoverable. Lift them apart now, while they are still wet, not later when they have started to dry. If they are already blocking, do not force them; keep them wet and get advice.
3. Keep them wet if you cannot dry them properly today. Counter-intuitive but correct: a wet print in a sealed bag in a cold room is stable for days. A half-dried print in a warm room is a mould farm. Choose deliberately between drying now and freezing now.
4. Separate the hopeless from the rest, but do not throw anything away yet. An assessor may need to see it, and "hopeless" is a judgement that is easy to get wrong when you are standing in a wet room at midnight.

Handle wet prints by the edges, supporting them flat with a rigid board — a plastic chopping board or a piece of cardboard covered in cling film. A wet print lifted by one corner tears along the wet line.

How to air-dry prints without fusing them together.

1. Work in a cool room with moving air. A fan moving air across the room, not pointed directly at the prints. Warmth is not your friend — it accelerates mould and makes the emulsion cockle.
2. Image side up, on an absorbent surface. Blotting paper, unprinted newsprint, or plain white kitchen paper, changed as it becomes damp. Never lay prints face down: the emulsion will stick to whatever it is resting on.
3. One layer, spaced apart, never overlapping. The whole job is preventing contact.
4. Change the blotting layer every few hours for the first day. Prints sitting on damp paper do not dry; they equilibrate.
5. Do not use a hairdryer, an oven, a radiator, a microwave or direct sun. Heat sets the cockling, can crack the emulsion, and drives mould growth rather than preventing it.

Expect prints to dry slightly wavy. That is normal and largely reversible under weight once they are thoroughly dry — a week later, between clean blotting paper and a board, with a light weight on top. Never press a print that is still damp; you will press the moisture in and flatten the texture permanently.

Negatives and slides are a different case. Wet film should not be allowed to dry in contact with anything, including itself. Keep it wet, in a container of clean water if necessary, and get it to a lab or a conservator quickly — drying film badly leaves permanent marks along the whole strip.

Freezing is the pause button. It is not damage.

This is the single most useful thing on this page, and the one people are most reluctant to believe. Photographic materials freeze well. Museums and archives routinely store photographs below freezing precisely because the chemistry that ages them slows almost to a stop. If you have more wet material than you can dry in two days, freezing is the correct answer, and it buys you months.

How to do it in a domestic freezer:

1. Interleave while wet. Wax paper or silicone paper between prints, or small groups of prints in a sealed bag with the air pressed out. The interleaving is what stops them blocking.
2. Bag and label. Sealed freezer bags, moisture and air out. Label each bag with the contents and the date, in permanent marker on the outside. You will not remember.
3. Freeze at the coldest setting you have, and keep it steady. A domestic freezer at −18°C is fine. Fluctuation is worse than the temperature itself.
4. Thaw in small batches, and only when you can finish the job. Take out one bag, let it thaw in its bag at room temperature, then dry it properly as above. Do not thaw the lot and leave it.

Two caveats. Do not freeze glass plate negatives or anything with flaking, lifting emulsion without advice — the water in the cracks expands. And do not freeze a wet item and then bring it out into a warm, humid room to "check on it": condensation will form on every surface, and repeated freeze-thaw cycles are much harder on the material than one long freeze.

If it is already mouldy, treat it as a hazard, not a stain.

Mould on photographs is a health issue as well as a conservation issue. Spores are a respiratory irritant, and the visible fuzz is a fraction of what is in the air around it.

• Protect yourself. Nitrile gloves and a properly fitted mask — FFP2/N95 at minimum — and work somewhere ventilated, away from anyone with asthma or a compromised immune system. Do this before you are sentimental about the photographs.
• Isolate immediately. Mouldy items go into a sealed bag or a separate box, away from everything else you own. Cross-contamination is how one mouldy album becomes a mouldy collection.
• Do not dry-brush it. Brushing, shaking or vacuuming with an ordinary vacuum launches spores into the room and spreads the infection. Surface mould that must be removed is a job for a conservator with the right equipment.
• Do not use bleach, disinfectant, fungicide or vinegar on a photograph. These attack the emulsion. There is no household product that makes a mouldy print safe and unchanged.
• Dry it, then get advice. Mould cannot grow below about 65% relative humidity, so drying is the first control. After that, a conservator can tell you whether the item is treatable, and whether the image survives in a usable form.

The photograph may still be worth keeping even if it is stained — as a record, and as raw material for digital restoration, which handles staining better than it handles missing pieces. What is not worth doing is putting a mouldy print back in a box with clean ones.

Insurance, records, and the reason this will not happen twice.

Once the material is stable, three things are worth doing while the details are fresh.

• Write the damage report. What was affected, what was lost, what was dried, what was frozen and when. Insurers ask for this months later, and memory is poor. Photographs of the original state plus a dated list are usually enough.
• Scan the recovered items, in priority order. The order is not "the prettiest". It is: the only surviving photographs of people, then the oldest processes, then the mid-century colour prints, then the rest. If you only get through the first category, you have saved the collection's real value.
• Change where they live. Water damage is nearly always a storage decision: a box on a garage floor, a shelf under a bathroom, an album against an outside wall, a loft that swings between 5°C and 40°C. The storage guide is the page that stops this happening again, and it is cheaper than the drying.

And one thing to keep in perspective: most wet family photographs are recoverable, and the ones that are not are usually lost to handling rather than to water. The instinct to pull them apart, wipe them and dry them near a heater is what does the damage. Slowness is the technique.