Standardizing at 75 deg F......

[Brian B Bednarek]

Ditto. My only concerns are when the film development time drops below five minutes, then I start earlier the next day or turn on the air conditioner.

You can always dilute the developer and adjust the time accordingly.

 

[bernard_L]

Nice and fine when there is a specific temperature compensation table/graph given by the manufacturer for film "F" in developer "D", as shown by Matt King in https://www.photrio.com/forum/threads/standardizing-at-75-deg-f.197438/post-2648674. But one should not assume that there is a universal temperature-time compensation law, as, e.g. published by Iford

Not all reducing molecules have the same rate of change of activity versus temperature, and when --as commonly happens-- there are two reducing agents in one developer, the balance between the two might change with temperature.

A counter-example showing that temperature compensation is not universal can be found in
Technical Data Agfa B/W Chemicals – Film processing

Going from 24 to 18°C. APX100 time ratio 10/4=2.5; APX400 11/8=1.375. Significant! In the same document, APX400 in Studional 7.3/4=1.825. etc... Some or all of films/developers being obsolete is not the point. The point is I put a counter-example on the table.

As for myself, I aim to be within ±1°C of a 20°C goal, and compensate for the residual difference (measured in-tank at mid-processing time) at a rate of 10% per °C.

 

[Ian Grant]

A counter-example showing that temperature compensation is not universal can be found in
Technical Data Agfa B/W Chemicals – Film processing
View attachment 330118
Going from 24 to 18°C. APX100 time ratio 10/4=2.5; APX400 11/8=1.375. Significant! In the same document, APX400 in Studional 7.3/4=1.825. etc... Some or all of films/developers being obsolete is not the point. The point is I put a counter-example on the table.

As for myself, I aim to be within ±1°C of a 20°C goal, and compensate for the residual difference (measured in-tank at mid-processing time) at a rate of 10% per °C.

It's also not universal when it comes to developers, somewhere I have a similar graph showing different slopes for Ilford developers.

Ian

 

[Sirius Glass]

You can always dilute the developer and adjust the time accordingly.

I eschew that because I use XTOL-R long term. I rather turn on the air conditioner for a few hours.

 

[Sirius Glass]

Nice and fine when there is a specific temperature compensation table/graph given by the manufacturer for film "F" in developer "D", as shown by Matt King in https://www.photrio.com/forum/threads/standardizing-at-75-deg-f.197438/post-2648674. But one should not assume that there is a universal temperature-time compensation law, as, e.g. published by Iford
View attachment 330117
Not all reducing molecules have the same rate of change of activity versus temperature, and when --as commonly happens-- there are two reducing agents in one developer, the balance between the two might change with temperature.

A counter-example showing that temperature compensation is not universal can be found in
Technical Data Agfa B/W Chemicals – Film processing
View attachment 330118
Going from 24 to 18°C. APX100 time ratio 10/4=2.5; APX400 11/8=1.375. Significant! In the same document, APX400 in Studional 7.3/4=1.825. etc... Some or all of films/developers being obsolete is not the point. The point is I put a counter-example on the table.

As for myself, I aim to be within ±1°C of a 20°C goal, and compensate for the residual difference (measured in-tank at mid-processing time) at a rate of 10% per °C.

It's also not universal when it comes to developers, somewhere I have a similar graph showing different slopes for Ilford developers.

Ian

I always figured that each developer had its own specific temperature compensation table/graph. Thank you for confirming that.

 

[Ian Grant]

I always figured that each developer had its own specific temperature compensation table/graph. Thank you for confirming that.

Each developer has its own Temperature Coefficient, that's determined by the developing agent or agents, and also choice of alkali as well as the balance of the overall formula. In practice most of the modern fine grain film developers we use won't be far different in this respect, and we would fine tune based on the manufacturers recommendations.

It gets more complicated because the Coefficient is also dependent on the scale used - ºF or ºC, in terms of ºF the coefficient is based on a 10ºF difference in temperature, and varies from approx 1.8 for an MQ developer (print/plate),1.6 for a typical Fine Grain developer, to 2.3 for a Super Fine Grain developer like Sease etc, which are not used today.

There are other factors that come into play Metol works poorly at low temperatures, it's Isomer p-Aminophenol (used in Rodinal) doesn't nor dies Phenidone (or Dimezone), this can make a huge difference if printing with an MQ developer and the temperature drops below 20ºC.

Ian

 

[Roger Cole]

I do!

Even in the Netherlands, 20 deg Celsius requires some developer cooling during the summer time. Using a Jobo temper bath, warming up developer, water baths and fixer to the same consistent temperature is way more easier than cooling down using ice cubes and what not. I also do two pre-soaks to minimize a temperature drop when pouring in the developer.

Same (different developer.) Here in GA my un-air conditioned basement darkroom is often in the mid to upper 70s F in summer. Evaporative cooling means room temperature solutions will be a bit cooler of course. Water comes out of the tap at nearly 80F in summer. I can still use my Jobo and warm solutions a degree or so (F) to 75F. At very worst on the hottest days a little time adjustment for slightly warmer temperature adn it won't be enough to worry about. In winter the darkroom IS heated so I can have it whatever I want. 75F/24C is low enough not to (usually) give too-short times, but warm enough to mean heating at least slightly where my Jobo can maintain the temperature, at least the vast majority of the time. We might have a week or two heat wave in the summer where I'd have to fool with cooling (as you say, much harder) or just take a bit off the time.

And as others have said, the really important thing is that all temperatures, including wash water, be as close as possible though I can believe that this is less important now than when I tested it and formed my opinion on the matter in the late 1970s.