A fibre-based print judged wet under the safelight almost never matches the print held in the hand the next morning. The dry version reads slightly darker, and its highlights have lost a measure of separation. This shift, known as dry-down, is one of the most common reasons a carefully assessed wet print disappoints once finished. Because the judgement is made wet but the result is viewed dry, the discrepancy is built into the process unless it is anticipated.

What causes the shift

Dry-down is a genuine increase in image density that occurs as the gelatin emulsion and the paper base lose water. A saturated emulsion is swollen and translucent; as it dries it tightens and contracts, and the developed silver becomes optically denser. Fibre paper compounds the effect because its absorbent cotton base takes up and then releases a great deal of water, so the emulsion it carries dries more profoundly than on a non-absorbent support. The change is small in absolute terms but disproportionately visible in the lightest tones, where the eye is most sensitive to small density differences. The result is highlights that close up and an overall impression of slightly reduced contrast. Resin-coated papers, whose plastic base absorbs almost no water, show far less of the effect, which is why dry-down is discussed chiefly in the context of fibre printing.

Measuring the dry-down factor

The shift is reproducible for a given paper, so it can be measured and treated as a constant. The printer Les McLean describes a direct comparison method: make one straight reference print at the chosen base exposure, then make a series of identical prints with that exposure reduced by 8, 9, 10, 11 and 12 per cent. The reference is kept wet in a holding tray while the series is dried fully. The dried print that matches the wet reference identifies the paper’s dry-down percentage. McLean notes that the factor for most fibre papers falls between 8 and 12 per cent, and that papers should be retested periodically because emulsion characteristics change over time.

Compensating in exposure and contrast

Once the factor is known, all printing decisions, including burning and dodging, are still judged on the wet print, and the correction is applied only to the final exposure. Reducing the base exposure by the measured percentage lightens the wet print so that drying brings it down to the intended density: a 20-second base at a 10 per cent factor becomes 18 seconds. Because dry-down also flattens the highlights, a small contrast increase, often a fraction of a paper grade, can restore the separation lost in the upper tones. Alternatively, the wet print may be inspected under a dimmed viewing light calibrated to mimic the appearance of the dry print, removing the need to calculate at all.