Kentmere 400 pushed to 800 or 1600 with Rodinal

[loccdor]

Interesting. I think I've always used Rodinal immediately after mixing.

 

[koraks]

With Rodinal, it seems highly prone to aerial oxidation at working strength.

Okay, but if that's the issue at hand here, I think the example posted by @Milpool above says enough. Yes, rodinal oxidizes readily, but it'll work fine for 1 hour at least, even at 1+100. So it's not as extreme as you make this out to be. Other developers can be more problematic in this regard; esp. staining developers like 510 pyro.

 

[Lachlan Young]

Okay, but if that's the issue at hand here, I think the example posted by @Milpool above says enough. Yes, rodinal oxidizes readily, but it'll work fine for 1 hour at least, even at 1+100. So it's not as extreme as you make this out to be. Other developers can be more problematic in this regard; esp. staining developers like 510 pyro.

With some films, with enough solution volume - which does not equal all films. The test was also done to look into stand development - if you add enough agitation to resolve the major uneveness that @Milpool mentions, that will effectively aerate the developer too, unless you use nitrogen gas burst (I think some of the testing by others was done with regular agitation). A density/ time curve would demonstrate when diminishing returns rapidly set in, but would require much more extensive work.

I'd also add that the 30 min result is roughly equal to what Agfa (US) suggested would be the outcome of 20 mins with regular agitation, and that the average gradients and curve shapes tell a key story about something that can be achieved in much less time with Xtol and regular agitation (and the potential to land higher aim densities).

 

[koraks]

As to the agitation - sure, it would make a difference. The other points, I'm more skeptical about. There's not enough dissolved oxygen in any film to explain why rodinal at any sensible dilution would deplete after 30 minutes with one film but not another. The notion of curve shapes and gradients all nice and all, but not directly related to the question whether rodinal poops out after half an our.

I think @Milpool's test shows beyond any reasonable doubt that what you said earlier was exaggerated. There might (will) be diminishing returns, but that doesn't place them at firm zero after 30 minutes as you implied earlier.