They are allowing some time for the dissolved Oxygen to be "used up". One has to keep in mind the amount of dissolved Oxygen is quite variable depending on whether the water is coming out of a tap strongly aerated vs out of a bottle etc. Further, there could be several mechanisms at work with dissolved Oxygen. This is why on balance, I would have to say anyone worrying about this is likely trying for some kind of tolerance well within the margin of error. If it were a problem of any materiality it would be addressed in the mixing instructions. Neither Kodak (D-76) nor Ilford (ID-11) indicate a stand period is necessary.
I will also check Haist tonight as D-76 is an example given in the mixing chapter.
Last edited by Michael R 1974; 03-04-2013 at 04:02 PM. Click to view previous post history.
Yes Clive, I was referring to the oxygen present in the water (or developer stock solution), not the one that dissolves when left in an open container.
I also mix my developer the same way as you do.
I only quoted PE to highlight that the problem is real, on the other hand ID-11/D76 is pretty robust and my system is not that precise that I could point with great certainty any variations in negative density to the aging of my developer.
All HQ developers undergo a tiny change during the first few hours after mixing
due to the consumption of dissolved oxygen and formation of HQMS
(Hydroquinone Monosulfonate). This usually causes an increase and then decrease
in activity depending on how much oxygen was entrained during mixing and how
the mixed developer was stored.
Last edited by Aron; 03-04-2013 at 04:09 PM. Click to view previous post history.
When I was developing sensitometric film tests, I used both a freshly made up, and a two weeks old XTol. I did not see any discontinuity in the curves, but I have not done a direct comparison, I'm afraid. I'm curious to hear what others think.
I've not seen much in the way of density variation with XTOL which is one of the reasons I'm inclined towards it. I had too many unpleasant surprises when I previously used Pyrocat-HD a few years ago; partly related to unpredictable responses to oxidation I suspect.
Well I checked Haist and he says nothing about letting photographic solutions, including D-76, stand after mixing other than to allow them to cool to working temperatures. So that's Haist, Kodak and Ilford. I'm convinced.
Let's be clear on a few things here:
1. OP is mixing XTOL which does not contain HQ
2. We cannot compare the stability of mild-pH solvent developers such as XTOL and D-76 with that of low-sulfite staining formulas containing Pyro or Catechol.
a) Note PE says a tiny change due to the consumption of dissolved Oxygen and formation of HQMS in developers containing HQ. This is probably all within the margin of experimental error when developing film. Not sure what measurable effect if any this has at the working pH of fresh D-76.
b) PE points out this depends on the amount of dissolved Oxygen present in the first place. OP says he's using distilled water, which to me means he's pouring it relatively gently from some vessel, not spraying it from a fire hose and then violently mixing it.
I let my developer solution "rest" overnight but the reason I do that is not the oxygen content or the Ph issue. With D76 and XTOL, right after mixing I see some undissolved particles floating around. I do not want them landing on film during processing and causing spots and uneven processing. In few hours, they will completely dissolve. So I mix, decanter into smaller bottles and seal, then 24 hours (or more) later, I use them for processing.