PMK: how much to adjust for higher temps?

Foto Ludens · Jun 4, 2021

Hi all,

As I returned to the darkroom after a long hiatus, I realized that using Rodinal in the summer is problematic (water temperatures are too high here in the 3rd coast). In the past I used Jay DeFehr's 510 Pyro in the Texas summer, but as I was unable to find it pre-mixed I decided to order some Photographer's Formulary PMK instead. I have managed to snag a copy of The Book of Pyro on eBay, but it will probably take another few days to get here. Until then, I'd like to develop a roll or two in 75-80 degree (farenheit) water temperatures if possible.

So, does anyone know how much to adjust published developing temperatures for each degree above 68? I had found an answer to this a few days ago, but my internet Kung Fu is weak today. I can't remember if it's 4% or 8% less time for each degree of added temp (or is it 12?)...

Thanks in advance!

André

DMJ · Jun 4, 2021

You can use the mass dev chart online.

Knowing this:

http://stores.photoformulary.com/content/01-5060.pdf

And adjusting:
https://www.digitaltruth.com/devchart.php?doc=timetemp

Or bring the water to desired temperature and put the tank in a water bath at the same temperature ?

Foto Ludens · Jun 4, 2021

Ah, of course, the PMK documentation! Doh! I knew I'd seen a table somewhere... I just forgot to look in the obvious place.

The digital truth conversion widget is very helpful as well. Thanks!

john_s · Jun 4, 2021

There is a table in The Book of Pyro which will answer that question. My copy is not here so I can't copy the page for you.

Foto Ludens · Jun 4, 2021

john_s said:
There is a table in The Book of Pyro which will answer that question. My copy is not here so I can't copy the page for you.

Thanks John. Waiting for my copy of the book to arrive would be the prudent thing to do... I'm looking forward to reading that!

Foto Ludens · Jun 4, 2021

According to the Photographer's Formulary documentation DMJ linked to above, the answer is 4% less time per degree (F). I'm curious to see if the Book of Pyro differs from that, but this gives me a solid starting point... Thanks again, all.

juan · Jun 4, 2021

I’ve never used PMK but with other developers I’ve. Used the 4% per degree formula.

ic-racer · Jun 4, 2021

Back before I got a temperature regulated Jobo film processor, I determined the following based on the films and developers I was using at the time (1980s).

New Time = (x * B + y) * Log (New Temp) + B

Where:
B = (Old Time - (Old Temp * y) / (1 + Old Temp * x)
y = -0.576929
x = 0.620567

Foto Ludens · Jun 4, 2021

ic-racer said:
Back before I got a temperature regulated Jobo film processor, I determined the following based on the films and developers I was using at the time (1980s).

New Time = (x * B + y) * Log (New Temp) + B

Where:
B = (Old Time - (Old Temp * y) / (1 + Old Temp * x)
y = -0.576929
x = 0.620567

That's... well... erm... not quite as intuitive as I hoped

I appreciate it, though. I went with the "4% per degree" rule and ended up with some very nice looking negatives. We'll see how they work out once dry!

john_s · Jun 4, 2021

Also, depending on how much air contact the PMK is exposed to in the developing tank, extra time might make not much difference. I found that trying to get extra contrast by developing for longer made hardly any difference to the resulting contrast. This was using only 250mL for a 36 exposure roll with very minimal amount of air in he tank. These days I would try 500mL or more if I wanted more than very moderate contrast.

Foto Ludens · Jun 4, 2021

john_s said:
Also, depending on how much air contact the PMK is exposed to in the developing tank, extra time might make not much difference. I found that trying to get extra contrast by developing for longer made hardly any difference to the resulting contrast. This was using only 250mL for a 36 exposure roll with very minimal amount of air in he tank. These days I would try 500mL or more if I wanted more than very moderate contrast.

That's good to know. I went with 500ml (2 reel tank) and one 36 exposure roll, mostly for the sake of consistency when developing 35mm and 120 film. These negatives don't look overdeveloped, but we'll see how they scan tomorrow....

DMJ · Jun 5, 2021

All your answers are in the second page of the PDF I linked above

"CAPACITY OF PMK PMK is a one-shot developer. Because it is so dilute, a minimum of 300 ml of developer per 80 square inches of film (one roll of 36 exposure 35 mm film, or four 4 by 5 negatives) must be present in the tank or tray. Inconsistencies can result by varying the ratio of film to quantity of developer used. Best results will be obtained by keeping the amount of PMK per roll consistent.

FILM DEVELOPMENT TEMPERATURE The conventional temperature for film development is 68°F (20° C) or 70° F. During the summer month in many parts of the country, cold tap water is often much warmer than 70° F. For PMK each degree of increased developer temperature, decrease the development time by 4%. Do not hesitate to use the higher temperatures. With appropriate reduction in development time, no loss of quality in the negative will result.

Foto Ludens · Jun 5, 2021

Hahahaha... I had read it when you posted it, and even noted the temperature bit above. But somehow I forgot about the capacity bit by the time John posted. That's what I get for posting at night!

RalphLambrecht · Jun 5, 2021

Andre R. de Avillez said:
Hi all,

As I returned to the darkroom after a long hiatus, I realized that using Rodinal in the summer is problematic (water temperatures are too high here in the 3rd coast). In the past I used Jay DeFehr's 510 Pyro in the Texas summer, but as I was unable to find it pre-mixed I decided to order some Photographer's Formulary PMK instead. I have managed to snag a copy of The Book of Pyro on eBay, but it will probably take another few days to get here. Until then, I'd like to develop a roll or two in 75-80 degree (farenheit) water temperatures if possible.

So, does anyone know how much to adjust published developing temperatures for each degree above 68? I had found an answer to this a few days ago, but my internet Kung Fu is weak today. I can't remember if it's 4% or 8% less time for each degree of added temp (or is it 12?)...

Thanks in advance!

André

google for a temp adjustment chart ublished by Ilford. it is very good and wrks for all films and developers.

DMJ · Jun 5, 2021

Andre R. de Avillez said:
Hahahaha... I had read it when you posted it, and even noted the temperature bit above. But somehow I forgot about the capacity bit by the time John posted. That's what I get for posting at night!

Long time ago...when I was in college, a professor used to say "when all else fails, read the manual" LOL

Andrew O'Neill · Jun 5, 2021

I always refer to Ilford's time temperature chart. Google it.

Doremus Scudder · Jun 5, 2021

RalphLambrecht said:
google for a temp adjustment chart ublished by Ilford. it is very good and wrks for all films and developers.

Here: https://www.ilfordphoto.com/wp/wp-content/uploads/2017/03/Temperature-compensation-chart.pdf

DMJ · Jun 5, 2021

Doremus Scudder said:
Here: https://www.ilfordphoto.com/wp/wp-content/uploads/2017/03/Temperature-compensation-chart.pdf

One of those things to have printed and laminated hanging in the darkroom.

Foto Ludens · Jun 5, 2021

DMJ said:
One of those things to have printed and laminated hanging in the darkroom.

That is a handy chart...

Foto Ludens · Jun 5, 2021

michael_r said:
In Hutchings’s book he says decrease developing time by 4% for every degree increase in temperature. However it is not clear how he calculates. He then says something a little different in the next paragraph: as a starting point at 80F try 70% of the 70F time for normal contrast, for N+1 at 80F try 65% of the N+1 70F time, etc. In the appendix tables where he gives his preferred development times for some Kodak and Ilford films, for normal contrast the 80F times seem to generally be in the range 60-70% of the 70F times.

There’s quite a bit of questionable info in that book overall so don’t get too caught up in it.

Good to know. I'm looking forward to the book anyway -- It's been a long time since I developed with pyro, and I never had much technical knowledge about it to begin with. I'm looking forward to learning what I can!

Foto Ludens · Jun 5, 2021

DMJ said:
Long time ago...when I was in college, a professor used to say "when all else fails, read the manual" LOL

That's pretty much what I tell my students... At least my faux pas is hidden behind a pseudonym... oh, wait...

john_s · Jun 5, 2021

DMJ said:
All your answers are in the second page of the PDF I linked above

"CAPACITY OF PMK PMK is a one-shot developer. Because it is so dilute, a minimum of 300 ml of developer per 80 square inches of film (one roll of 36 exposure 35 mm film, or four 4 by 5 negatives) must be present in the tank or tray. Inconsistencies can result by varying the ratio of film to quantity of developer used. Best results will be obtained by keeping the amount of PMK per roll consistent.

FILM DEVELOPMENT TEMPERATURE The conventional temperature for film development is 68°F (20° C) or 70° F. During the summer month in many parts of the country, cold tap water is often much warmer than 70° F. For PMK each degree of increased developer temperature, decrease the development time by 4%. Do not hesitate to use the higher temperatures. With appropriate reduction in development time, no loss of quality in the negative will result.

Although my comments above referred to me using 250mL, that is the nominal volume for the one-reel Jobo, but to minimize the amount of air, I filled it almost to the brim, leaving a bit of air to allow some movement in agitation. So the volume was actually close to 300mL. I agree that a larger volume is very preferable with such a developer.

Incidentally, I did some maths on the times in the table in The Book of Pyro and found that the rule of thumb (4% per degree) did not agree with the times he gave for specific films and temperatures. But probably any discrepancy would be cleared up in one's first test.

PMK: how much to adjust for higher temps?

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