Activity of developing agents as a function of temperature

[snusmumriken]

I just cut out and use the Ilfordphoto chart, seems to be close enough for most developers.
Films changed a lot since 1942, post 4.

https://www.ilfordphoto.com/amfile/file/download/file/1829/product/551/

There’s also the possibility that developing agents might have different time-temp behaviour in different developer formulations. But believing things have changed is as much an act of faith as believing they haven’t. I’m going to satisfy my curiosity. Just another thing to do. Sigh.

 

[alanrockwood]

Something interesting in post #4: at 20 C para aminophenol is less temperature sensitive than metol, and the same trend is accentuated as temperature goes up because the two lines curve in opposite directions.

Also interesting is that for some developers the traces are straight lines, but for others they are curves. Looking at this from the point of view of chemical kinetics, this likely indicates that for some developers (the ones with curved traces) there may be more than one one development mechanism, or perhaps more than one rate limiting step in a sequence of steps responsible for development.

 

[alanrockwood]

Great, thanks. So what I was heading towards was to make an Ilford-style time-temperature chart for a metol-only developer. I think this is right, but it would be kind if someone would check it.
View attachment 322934

It looks like your lines curve in the opposite direction compared to the metol curve in post #4. This suggests that there is something wrong, either in your calculation or in the information in the figure posted in post #4.

 

[Alan Johnson]

Something interesting in post #4: at 20 C para aminophenol is less temperature sensitive than metol, and the same trend is accentuated as temperature goes up because the two lines curve in opposite directions.

That may have been the case for 1942 films but as of 2022 the lines for metol [Perceptol, see link post 26] and for p-aminophenol [Adox Rodinal 1:50, see below] have virtually identical slopes and thus temperature coefficients.
eg, the change from 17min to 12 min is 4C in both cases.

https://www.fotoimpex.com/shop/images/products/media/56415_4_PDF-Datenblatt.pdf

 

[Romanko]

as of 2022 the lines for metol [Perceptol, see link post 26] and for p-aminophenol [Adox Rodinal 1:50, see below] have virtually identical slopes

The curve for metol in post #4 is different from other curves. This is certainly interesting. Aparently, Mees used Chibisov's data who published his results in 1938 in Russian. Anyone aware of more recent (and obtainable) publications?

 

[albada]

I used the development times of 7.25, 6.5, 6.25, and 5.25 mins for temperatures of 18, 20, 21 and 24 degrees, respectively, for XTOL full strength solution and TMAX-400 at EI 400 developed to CI=0.56.

XTOL datasheet

The development time at 15 degrees is 8:31. What is your development time at 15 degrees?

7.25*1.1225^3 = 10.25 minutes for 15 degrees, which is far from 8:31. Did I botch the calculation?

 

[Romanko]

7.25*1.1225^3 = 10.25 minutes for 15 degrees, which is far from 8:31. Did I botch the calculation?

I am afraid you did. 21 -> 20 degree: 6.25*1.1225 = 7.0. The time for 21 degrees should be 6.5 min.

 

[snusmumriken]

It looks like your lines curve in the opposite direction compared to the metol curve in post #4. This suggests that there is something wrong, either in your calculation or in the information in the figure posted in post #4.

I don't think so. Here is the exact same graph but with a logarithmic time axis. I don’t pretend to understand how this happens mathematically, so thanks for making me check!

 

[snusmumriken]

The curve for metol in post #4 is different from other curves. This is certainly interesting. Aparently, Mees used Chibisov's data who published his results in 1938 in Russian. Anyone aware of more recent (and obtainable) publications?

I did a quick search on Google Scholar and found this. Barely more recent but available and in English.

 

[alanrockwood]

I don't think so. Here is the exact same graph but with a logarithmic time axis. I don’t pretend to understand how this happens mathematically, so thanks for making me check!
View attachment 323027

The plot in post #4 is already logarithmic on the y-axis.

 

[snusmumriken]

The plot in post #4 is already logarithmic on the y-axis.

Yes, exactly. So my second plot should look like post#4 - which it does, for that 17-25 deg temperature range.

But I think I see what you are saying. To model the (presumably data-based) curve in post #4 over lower temperatures, there perhaps needs to be another term in the model?

 

[Romanko]

I did a quick search on Google Scholar and found this. Barely more recent but available and in English.

Thank you for the reference. I plotted the logarithm of induction time for metol as a function of temperature using the data in Table 1. There appears to be "gentle convexity" similar to Mees's/Chibisov's data. Hydroquinone curve is also in agreement (see Fig.3), showing some "concavity". (Are there better mathematical terms for describing curves with second derivatives of different signs? Any high school graduates here?)

There is a typo in Table 1 and I could not reproduce the plot. Also note that the authors fitted a straight line to their data points.

Even for a single developing agent the theory is quite complex and the model that we are using is only good for practical applications.

 

[alanrockwood]

Yes, exactly. So my second plot should look like post#4 - which it does, for that 17-25 deg temperature range.

But I think I see what you are saying. To model the (presumably data-based) curve in post #4 over lower temperatures, there perhaps needs to be another term in the model?

Yes, another term in the model is a reasonable interpretation.

 

[Romanko]

Yes, another term in the model is a reasonable interpretation.

You can try:
dev_time = exp(a + b * T + c * T * T )
or
dev_time = exp(a + b * T + c * T * T + d * T * T * T )
or even fit a spline to the curves in post #4. This could give you better accuracy than a linear regression model. It should be understood that these models do not necessarily reflect the theory of development, it is just a convenient way to approximate experimental data.

 

[redbandit]

Well did you consider that most of the film chemicals will give you very nice ranges to use when using them?

ie

develop our paper for at least 1 minute, fix for at least 2 minutes

develop paper for 60-90 seconds, stop bath for at least 10 seconds and fix for at least 60 seconds.

Even if you dont hit the "ideal" temperature range, staying inside those time will get at least a satisfactory processing time

 

[Romanko]

Well did you consider that most of the film chemicals will give you very nice ranges to use when using them?

If I understood you correctly, you are saying that there is a certain range around your target temperature that would give you perfectly acceptable prints (in your example) or negatives.
I totally agree with you here. The reason I started this thread was to find out how far this target temperature could deviate from our usual 18 - 24 degree Celcius range. Obviously, you don't want to use very high temperatures that would melt your emulsion. I was wondering if there is a low temperature limit. There are "arctic" developers that work all the way down to -30 degrees. I believe they could go further but Propylene Glycol solution that they use starts to freeze at about -40 degrees.
And no, I have no practical reasons to develop film at -30 degrees in Australia. I am just curious.

 

[redbandit]

If I understood you correctly, you are saying that there is a certain range around your target temperature that would give you perfectly acceptable prints (in your example) or negatives.
I totally agree with you here. The reason I started this thread was to find out how far this target temperature could deviate from our usual 18 - 24 degree Celcius range. Obviously, you don't want to use very high temperatures that would melt your emulsion. I was wondering if there is a low temperature limit. There are "arctic" developers that work all the way down to -30 degrees. I believe they could go further but Propylene Glycol solution that they use starts to freeze at about -40 degrees.
And no, I have no practical reasons to develop film at -30 degrees in Australia. I am just curious.

well i have read about guys stand developing film with rodinal in antarctica, so it really does become a natural conclusion of

 

[psmithp]

I vaguely remember seeing a figure showing activity of developing agents as a function of temperature. It looked somewhat similar to the density vs. pH plot below. I can't remember where I saw it. It must have been in one of the old books. Any help is much appreciated.

View attachment 322802

(The curves are: 1 - metol, 2 - pyrogallol, 3 - hydroquinone, and 4 - paraphenylenediamine)

Go to Ilford https://www.ilfordphoto.com/technical-downloads/technical-data-sheets/#chemistry and download data sheets for their developers. They have nice graphs.

 

[Romanko]

Thank you for the link. I was looking specifically for activity of individual developing agents at reduced temperatures (see the plot in post #4). The kinetics of a complete developer could be more complicated. It would be good to know if Ilford's plots are based on measurements or they extrapolated the curves the way @snusmumriken did in post #13.

 

[snusmumriken]

I was looking specifically for activity of individual developing agents at reduced temperatures (see the plot in post #4). The kinetics of a complete developer could be more complicated.

Is it actually possible to measure that? Surely in any experiment a developing agent has to be supported with at least a favourable pH, and an anti-oxidant? Some ‘complete’ developer formulae are literally no more than that.

It would be good to know if Ilford's plots are based on measurements or they extrapolated the curves the way @snusmumriken did in post #13.

Just to be clear, ’extrapolated’ may not be the right word here. I used a section of the metol curve in post #4. I did not extrapolate beyond the temperature range of the curve. I have to assume that the original author had data for the full temperature range covered, through which he drew a curve (by eye?), which was itself a process of fitting a model to the data. What I did was also fitting a model (a mathematical one) to a part of the temperature range where a simple log-linear model (ie a straight line on the original axes) seemed a good fit. I then plotted it on linear axes for easy comprehension and perhaps use.

 

[Romanko]

Surely in any experiment a developing agent has to be supported with at least a favourable pH, and an anti-oxidant? Some ‘complete’ developer formulae are literally no more than that.

Correct. In the paper that you found they used a developing agent (metol or hydroquinone), sodium sulfite and sodium carbonate. This is a minimalistic "complete" developer. Most developers though have an anti-fogging agent and a restrainer that affect the kinetics.

Looking at the plot in post #1, metol seems to maintain some activity at pH 6-7. I am wondering if one can make a POTA-style developer with just metol?

Just to be clear, ’extrapolated’ may not be the right word here

Correct, again. You did not extrapolate the data you fitted it with a model. And using this model one can potentially extend the temperature range somewhat. This is what I did in my HC-110 example (post #6).

Thank you again for the paper, it explained the experiments really well.