Hypo spots on unexposed paper

Owned by chemistry in the bottle, because its cause is a bath in the wrong place rather than a bath in poor condition.

What you see

White spots on a print — pure paper white, with a sharp edge, in the shape of a drop or a splash or a fingertip — which are completely unaffected by exposure. Print the same negative darker and the spot stays white; print it lighter and the spot is still there.

Often several, in a scatter, sometimes with a run or a tail where the drop travelled.

On film the equivalent is a clear spot with the same properties, though it is far less common because film spends less time out of its packaging in a wet room.

Likely causes

1. A splash from the fixing tray reaching the dry side.
2. A hand that had been in the fixer taking a sheet from the box.
3. Wet tongs or a wet sleeve laid on the dry bench where the paper is handled.
4. The paper box stored in the wet area, so that the splash reaches the whole packet rather than one sheet.
5. A drip from a drying line or a squeegee run over the dry bench.

What is happening: the chemistry and physics

Photographic paper works because it carries silver halide crystals in gelatin. Exposure makes some of them developable; development turns those into silver; fixing dissolves the rest.

A drop of fixer on dry, unexposed paper performs the last step first. The thiosulfate complexes and removes the silver halide at that spot, and it does so quickly: ILFORD’s published fixing times for paper are 30 seconds for RC and 1 minute for fibre at 1+4 — that is how fast this chemistry clears a paper emulsion when it has full access to it.

So by the time the sheet reaches the enlarger, there is no light-sensitive material at that spot. Nothing can be exposed, nothing can be developed, and the paper base shows through.

!The confirming test, and the reason no printing decision helps

Expose a sheet from the same box to full room light, develop it, and look.

A normally handled sheet goes to a uniform maximum black. A sheet carrying hypo spots shows them as white marks on that black, because the spots had nothing to develop.

That is the confirming test, it costs one sheet, and it distinguishes this fault from everything it might be confused with: a dust spot on the negative prints white too, but moves when the negative moves; a coating defect is confined to a hand-made emulsion; and an air bell in the print developer gives a white spot that is not present on a fully exposed sheet from the same box.

And it explains why no printing decision helps. Burning-in adds exposure; exposure needs halide; the halide is gone. Dodging, grade, a longer development — none of them touch it.

The reverse contamination is the more famous one and it is a different fault: fixer in the developer ruins a bath and is covered by developer contaminated by fixer or stop. This entry is fixer on the paper, and it ruins one sheet at a time — or a whole packet, if the box was the thing that got splashed.

Diagnostic questions

• Is the spot pure paper white, with a sharp edge? Yes points here. A soft grey mark is something else.
• Does it survive more exposure? The decisive question, and it is free: it is on every print from that sheet at every exposure.
• Does it move when the negative moves? If it does, it is dust or a mark on the negative rather than on the paper.
• Is it on more than one sheet, in similar places? Then the packet was splashed rather than the sheet, and the rest of the box is suspect.
• Where is the paper stored and where is it opened? Wet side or dry side.
• Do you rinse and dry your hands between the fixer tray and the paper box? Kodak’s own layout recommendation asks for a container of water and a clean towel for exactly this.
• Is the mark shaped like a fingertip? That names the route.

Corrective action

None, on the print or on the sheet. The halide is gone. Spotting the print with a dye can disguise a small mark on a finished print, and that is a cosmetic repair rather than a fix.

Test the rest of the packet with the full-exposure sheet described above before printing anything that matters on it. A splashed box is worth knowing about before you have made twenty prints from it.

Prevention

Separate wet and dry. Kodak’s Z-133 states it as a facility recommendation: divide the darkroom into a wet area and a dry area, use the dry area for enlarging, printing and handling film, negatives and paper, and use the wet area for mixing and all processing operations. That single arrangement prevents most of the routes on this page.

Keep a container of water for rinsing hands, and a clean towel, and use both between the trays and the paper — again Kodak’s own instruction, and the reason it is in their publication is that this is not a theoretical risk.

Keep the paper box closed and on the dry side, and never on the bench beside the fixer tray.

One tong per tray, and never a tong laid on the dry bench.

Avoid splashing, which Kodak name as one of the four contamination routes and address with the plainest possible recommendation: good housekeeping, and care when lifting and transferring.

And store the paper as the maker asks — cool, dry, in its original packaging, away from high temperature and humidity — because a box that has been opened in a wet room has more wrong with it than a splash.