Exhausted developer

Owned by Chemistry in the Bottle, which separates the four failures that share one name and gives the shape that identifies this one: exhaustion is a slope, a contrast index falling film by film roughly in proportion to the loading, where oxidation is a plateau followed by a collapse. It follows that the diagnostic question is what the last four films looked like rather than what this one looks like. This entry was written before that page, from Break/Fix — the developer that went wrong, bottle D.

What you see

A solution that may be slightly yellowed but need not be. A strip that is thin and flat — and that has a lower fog floor than the control’s, with its threshold further down the wedge. An activity strip lighter than fresh.

That lower fog floor is the whole diagnosis, and it is counter-intuitive, which is why it is worth having in an atlas.

Likely causes

1. More work put through the bath than its published capacity allows.
2. No time compensation applied as the running total rose.
3. A working solution reused beyond its rating on the grounds that it still looked all right.

What is happening: the chemistry and physics

An exhausted bath has lost agent to silver rather than to air, and that is only half of it.

ILFORD state the other half — each film processed releases halides and other by-products into the developer that act as a restrainer on the development of subsequent films. So an exhausted bath is a weakened developer with a restrainer in it, and a restrainer has a published signature — fog down first, threshold down after.

That is the discriminator. Oxidation removes agent and adds nothing. Exhaustion removes agent and adds bromide. Both give thin and flat; only one gives a cleaner unexposed patch than the control.

Diagnostic questions

• Rank the fog floor against clear fixed base and against a control. Lower than the control’s is this entry. About the same is oxidation. Higher is chemical fog.
• The capacity log against the published figure. Kodak’s table gives four 135-36 rolls per litre, so 250 ml is rated for one roll, with a 15 per cent time increase after every four rolls per gallon. ILFORD’s parallel table says the same thing in the other direction — 10 per cent more time for each successive film in a litre, to a maximum of ten films at plus 90 per cent.
• A second strip at twice the time. Hurter and Driffield established that a restrainer retards rather than stops, and that the image will appear in full force if sufficient time be allowed. A bath held back mainly by bromide should recover a great deal at double the time. A bath that has simply lost its agent should recover less. That is a prediction with a direction, and it is worth one strip.
• The 60-second activity strip beside a fresh control, which measures what you actually care about.

📓Capacity and exhaustion are not the same word

Capacity is a published figure for how much work a volume of bath is rated to do. Exhaustion is the state of having done it. The course keeps them apart because a bath can be within its capacity and behaving badly, or past its capacity and still working, and only the log plus a test tells you which.

Corrective action

Discard it, and start counting.

A capacity log is four columns — date, what went through, running total, time compensation applied — and it is the difference between using a developer to its published capacity and using it past it.

Kodak’s route for a working bath is 15 per cent more time after every four rolls per gallon; ILFORD’s is 10 per cent per film in a litre to a maximum of ten. Neither is a licence to run a bath forever, and both stop.

Prevention

Keep the capacity log for every developer bottle you own, and write the published capacity at the top of it so that the running total has something to be measured against.

Compensate as you go rather than at the end. A bath that has had four times its rating with no compensation applied is four faults deep, not one.

Run a process-control strip before a session that matters, and rank its fog floor as well as reading its density. The fog floor is the reading that separates this fault from the one it most resembles.