Uneven toning

Owned by the two Part XX labs that meet it. Bleaching and redeveloping a sepia print files pale creamy patches after toning here, from bleached silver bromide the toner did not reach or a bath beginning to fail; selenium toning and the print curve files an uneven change across one piece here, with the two causes a bench actually produces — pieces overlapping in the dish, and agitation that stopped. The permanence half of the argument is toning, permanence and archival evidence’s. This entry was written earlier from Kodak’s G-23 and Part XII’s archival sequence.

What you see

A print whose tone changed in patches, or in streaks that follow the direction the print entered the bath, or more strongly at the edges than in the middle. Sometimes the unevenness is a difference of degree — some areas toned further — and sometimes it is a difference of colour.

Likely causes

Kodak’s own account is that most of them are not the toner at all.

1. Residual silver salts and traces of hypo, left by inadequate fixing or washing. Kodak put washing first in their own sequence for a reason: those residues “may cause stains, uneven tones and fading”.
2. A hardening fixer. Kodak recommend against one for prints intended for toning, because it makes the emulsion less receptive to the toner solution — and an emulsion that is unevenly hardened is unevenly receptive.
3. A dry print entered without soaking. Kodak’s instruction is to soak an already-dry print in water for two to three minutes before toning.
4. Earlier variation revealed late. Uneven development or an over-concentrated stop bath produce differences the untoned print did not show — that is mottle revealed after toning, which is the same phenomenon with a different first cause.

What is happening: the chemistry and physics

A toner is a reagent applied to a print, and every reagent applied to a print is applied through the gelatin. So two things govern how evenly it acts: how uniformly it can get in, and what it finds when it arrives.

Getting in is a swelling-and-diffusion problem. A dry print swells unevenly as it wets, and a print entered edge first is swelling at one edge while the toner is already working at that edge. Kodak’s soak instruction removes the first; agitation from the moment of immersion removes the second. A hardened emulsion swells less, and unevenly hardened gelatin swells unevenly — which is the mechanism behind Kodak’s advice against hardening fixers here.

What it finds is the other half, and it is chemistry the course already owns. Residual thiosulfate and residual silver are not distributed evenly through a badly washed print — they concentrate where washing was least effective, which is under a print lying against the bottom of a tray, or in the middle of a stack. So a wash fault produces a toning fault with a map of the wash tank on it.

!The confirming test: two tests before the toner, not after

Run a residual hypo and residual silver test on a scrap from the same batch, before toning anything you care about. Both residues are named by Kodak as causes of uneven tones, and both are testable in minutes.

• Residues present: the fault is fixing and washing. Kodak’s own figures are one hour for fibre-base prints with agitation and a complete change of water every five minutes, or four minutes for resin-coated — with prints agitated, kept separated, and the tank not overloaded.
• Residues absent: the fault is in the toning itself, and the next candidates are the soak, the entry, the agitation and the tray.

Then tone a test strip cut from the same print run rather than the print. Toning is irreversible and a strip costs nothing.

Diagnostic questions

• How was the print washed, and how many were in the tank? Kodak’s instruction to keep prints separated and not to overload is where most home washing fails.
• Was the fixer a hardening one? If so, that alone may account for it.
• Was the print dry when it went in? Then it needed a two-to-three-minute soak.
• What is the tray made of? Kodak: do not use metal trays or tanks for toning solutions — only unchipped enamel, hard rubber or plastic.
• Has the print been in storage? Kodak note that prints toned after storage may show stains due to adverse storage conditions, which makes an old print a poor test subject.

Corrective action

Toning is not reversible in this course. There is no assessed procedure here for removing a toner from a print, and the honest answer is to re-print.

Fix and wash properly, then tone. In that order, and with the residual tests as the gate between them.

Enter the print in one movement and agitate at once, especially in the first minute, which is Kodak’s own emphasis for the toners that act fastest.

Prevention

Follow Part XII’s archival sequence before toning anything, because everything it removes is something a toner would otherwise find.

Use a non-hardening fixer for prints you intend to tone.

Soak dry prints, use a non-metallic tray, and keep the batch small enough to agitate honestly.