Is there a general rule for temperature/time reaction rate when developing/stopping/fixing b&w print

Laci Toth · Sep 5, 2019

I’m just about to set up my darkroom but the place lacks of heating. The outside temperature usually doesn’t go below 9 celsius or if yes I won’t use the place on those days =) and there’ll be a foam insulation as well just to keep the place as warm and dry as I possibly can. At the moment I won’t be able to keep up with the bills if I’d use electric heating as I’m on a budget, I’m wondering how the temperature drop will affect the developing/stopping/fixing times? I know that it’s gonna be longer but is there any general rule for how the time will be longer with every celsius/fahrenheit?
I’ve read that a rough rule of thumb is that a reaction rate will double for a 10 celsius increase in temperature. Is this ‘correct’?

MattKing · Sep 5, 2019

For developing, find a Kodak Black and White Darkroom Dataguide and use the Development Dial to adjust between the times for 20C suggested by the manufacturer and the times appropriate for your working temperature.

Luckless · Sep 5, 2019

Most developers I've seen have a temp-time chart somewhere in their documentation.

https://www.ilfordphoto.com/amfile/file/download/file/1829/product/708/

Page 4 "For processing at other temperatures increase the given development times by 10% for each 1ºC (2ºF) drop in temperature"

Can't say with any confidence on the stop bath or fixing, but I also can't imagine much of an impact on stop bath if it is cold.

Biggest factor past the total development time is going to be making sure each stage is roughly similar in temp to the others. If you store everything together then you should be fine. But if you bring warm water in to mix up some fresh developer to use with the stop bath and fix that had been sitting there, then you may run into problems.

Or if you're bringing jugs of chemistry that are different volumes from one space into the other. [A half litre of developer will cool faster than a gallon jug of reusable fix for example]

But wash water seems to be the easiest trap to fall into if you're not watching. At least in my experience.

As a side note, consider looking at cheap options for solar gain during the cold months. Some plastic wrap over windows, and a large dark stone or some jugs of water where the sun hits can go a long way towards keeping the worst of the chill out of a small space.

Maris · Sep 5, 2019

The doubling of reaction rate for every 10 Celcius rise in temperature applies approximately for reactions that have first order kinetics. These are the simplest one step reactions where the reacting chemicals mix freely. Film development is more complex as it involves developer diffusing into an emulsion, development products diffusing out, and development products acting as a development restrainer while they are still in the emulsion.

Years ago I decided to do time and temperature development by controlling time but not temperature. Time control is very precise and repeatable while temperature control and stability both remain difficult parameters except at room ambient.
Here are my experimental results for N (normal) development of Tmax 400 sheet film with my Xtol in my darkroom:
14 Celcius ... develop for 20 minutes
24 Celcius ... develop for 7 minutes 35 seconds
34 Celcius ... develop for 2 minutes 45 seconds.

Doing all the testing can be tedious but once done and good notes kept the difficulties of temperature control go away. If you do similar tests your results will surely be different but just as useful.

Arklatexian · Sep 5, 2019

Laci Toth said:
I’m just about to set up my darkroom but the place lacks of heating. The outside temperature usually doesn’t go below 9 celsius or if yes I won’t use the place on those days =) and there’ll be a foam insulation as well just to keep the place as warm and dry as I possibly can. At the moment I won’t be able to keep up with the bills if I’d use electric heating as I’m on a budget, I’m wondering how the temperature drop will affect the developing/stopping/fixing times? I know that it’s gonna be longer but is there any general rule for how the time will be longer with every celsius/fahrenheit?
I’ve read that a rough rule of thumb is that a reaction rate will double for a 10 celsius increase in temperature. Is this ‘correct’?

Let me tell you my experience with heating my darkroom with electricity. When we built my darkroom, the only opening other than the doors was a small one for the air conditioner ( a "must" where I live. It is September and the next two days are predicted to reach 100 degrees F, actual temperature). The walls and ceiling are all insulated with fiberglass. My darkroom is 9 ft. x 16 ft. x 8 ft. high. That is not a large area to heat and an electric heater works well and with the temperature set at 68 degrees F (20 C) the heater is "off" more than it is "on". I have not noticed much of an increase in my electric bill. In my case, I can say the same about the air conditioner. Also it is much more convienent to have all of you liquids already at working temperature. You just need to keep some big bottles of water in your sink so they will be at 20C also.......Good Luck.....Regards!

pentaxuser · Sep 5, 2019

It really depends on firstly the ambient temperature in the room. Developing film or prints at less than say 16C may be risky. I take it that you have no direct access to a stream of hot water such as an Ascot type heater or even better a hot tap that draws water from a boiler some where as in a house hot water system. If not then is there an electric plug in the room and a platform on which you can rest an electric kettle. If there is then you have just to heat water and use it to balance the cold water.

Far better than this but it involves money is to buy a Nova slot processor which is heated but this will only help with prints and not developing although you could fill up one of the slots with plain water and heat that slot for water for developing.

If you are very short of cash you may have to forego developing in the coldest months if you can only do this in the darkroom. However if the rest of the house is heated then you could load the film into the tank in the darkroom and then develop in the heated part of the house. Once in the tank all processing can be done in daylight or room light

It might help if you can say exactly where you darkroom will be i.e. an outside shed/part of a garage/outhouse. Once we know we can target solutions to problems more easily

For the next month at least and possibly the next two the outside temperature should be good enough to keep the darkroom warm enough but it really depends on where the darkroom is

pentaxuser

Laci Toth · Sep 6, 2019

Thank you very much indeed for all of you for these very useful infos, I really appreciate them!
The darkroom would be in an outside shed with no electricity so I have to use an extension cord. It’s a very tiny space, approx. 1 meter wide, 2 meter long and 2 meter high.

Adrian Bacon · Sep 6, 2019

Arklatexian said:
Let me tell you my experience with heating my darkroom with electricity. When we built my darkroom, the only opening other than the doors was a small one for the air conditioner ( a "must" where I live. It is September and the next two days are predicted to reach 100 degrees F, actual temperature). The walls and ceiling are all insulated with fiberglass. My darkroom is 9 ft. x 16 ft. x 8 ft. high. That is not a large area to heat and an electric heater works well and with the temperature set at 68 degrees F (20 C) the heater is "off" more than it is "on". I have not noticed much of an increase in my electric bill. In my case, I can say the same about the air conditioner. Also it is much more convienent to have all of you liquids already at working temperature. You just need to keep some big bottles of water in your sink so they will be at 20C also.......Good Luck.....Regards!

+1

OP, your budget is so tight you can’t have a little space heater set at 20C? If it’s insulated that thing will be off more than it’s on.

Ozxplorer · Sep 6, 2019

You might find one of these gadgets helpful... or, search the internet for ideas using a “sous vide” adapted to your needs. Note, the earlier link is also available suitable for your voltage if purchased in Germany. Sorry my reply does not specifically answer your question but it does meet your need for maintaining controlled temperature condition.

Ian C · Sep 6, 2019

Here’s a 2009 APUG discussion on this topic:

https://www.photrio.com/forum/threads/chart-for-paper-developing-time-temperature.45043/

pentaxuser · Sep 6, 2019

Laci Toth said:
Thank you very much indeed for all of you for these very useful infos, I really appreciate them!
The darkroom would be in an outside shed with no electricity so I have to use an extension cord. It’s a very tiny space, approx. 1 meter wide, 2 meter long and 2 meter high.

Frankly unless it a lot different to the normal outside shed the insulation will be non existent and while mine is a garden shed which may be different from an outside shed then for a lot of the year my shed is either far too cold or unbearably hot. I think you either have to use it for quite limited periods of the year or consider the expense of insulation.

You could run an extension wire into the shed but it really needs to be protected by a sheath and not simply run along the ground from the likes of a plug in a house. If you are going to do any printing you will certainly need a safelight which means electricity

pentaxuser

Ozxplorer · Sep 6, 2019

Laci Toth said:
Thank you very much indeed for all of you for these very useful infos, I really appreciate them!
The darkroom would be in an outside shed with no electricity so I have to use an extension cord. It’s a very tiny space, approx. 1 meter wide, 2 meter long and 2 meter high.

Well, for roll film development there is no reason why it shouldn’t be done in indoors - say the kitchen/bathroom/laundry rather than use the shed. The temperature will then be much more easily maintained & within a reasonable range... load the tank/s inside of a film change bag designed for working under ambient light conditions. Setting up the shed for wet printing calls for a properly installed electrical supply (refer previous advice) for no other reason than your personal safety. And water supply? Otherwise, using the alternative printing method; it too becomes another in home activity!

jim10219 · Sep 6, 2019

Ozxplorer said:
Well, for roll film development there is no reason why it shouldn’t be done in indoors - say the kitchen/bathroom/laundry rather than use the shed. The temperature will then be much more easily maintained & within a reasonable range... load the tank/s inside of a film change bag designed for working under ambient light conditions. Setting up the shed for wet printing calls for a properly installed electrical supply (refer previous advice) for no other reason than your personal safety. And water supply? Otherwise, using the alternative printing method; it too becomes another in home activity!

Agreed. With a changing bag, you don't need to go into a dark room to develop roll film. You can even develop sheet film in a tank using the taco method. That'll make things easier. If you do need to develop sheet film in a tray, place your trays in a warm bath and keep a thermos nearby filled with hot water to maintain the temperature outside of the tray, which will help keep your chemicals at an appropriate temperature. It takes a while to get used to the process, but with some experience, it's not too hard to do. I have the opposite problem. I have to keep my chemicals cool in the summer, and I use a tray filled with ice water where I place my developer tray in. It floats a bit, but it allows me to control the temperature.

For prints, you may just want to wait until the weather cooperates. There are also larger tanks you can get to develop prints in, that you might consider. So you could expose the paper in the darkroom, place them in the tanks, and take them inside to develop and fix. It'll be a little bit harder since you won't be able to develop by inspection, but it can be done.

Laci Toth · Sep 6, 2019

Thanks for the further advices! I’ll use foam insulation anyway and there’s enough plug on the extension cord to operate the enlarger, the safelight and and also an electric kettle. I put the tray with the developer in a bigger tray so I could pour hot water to maintain the temperature or control it as much as I can.

John51 · Sep 7, 2019

You need a tray heater. Something like this:

https://www.ebay.co.uk/itm/Large-Ph...=true&nordt=true&rt=nc&_trksid=p2047675.l2557

It's only 300 watts and once warmed up, it will probably be off more than it's on.

Laci Toth · Sep 7, 2019

John51 said:
You need a tray heater. Something like this:

https://www.ebay.co.uk/itm/Large-Photography-Darkroom-Enlarging-Dish-Tray-Warming-Warmer-Plate-/254323405044?hash=item3b36db30f4:gcAAAOSwUUldSrKU&nma=true&si=aW%2BDuuelPA7MG0Is15xrz7iLYSw%3D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557

It's only 300 watts and once warmed up, it will probably be off more than it's on.

Thanks indeed! Will keep my eyes open!

MattKing · Sep 7, 2019

Murray Minchin is a very long term APUG/Photrio member who lives in Kitimat, BC and had similar concerns with tray temperatures.
As a result, he started one of my favourite APUG threads of all time - about pig fodder heaters!: https://www.photrio.com/forum/threads/sue-weeee.25459/#post-356431
The link in his post doesn't lead anymore to a current product, but the idea of using agricultural supply equipment is a good one.
Piglets apparently need to be kept warm .

David Lyga · Sep 7, 2019

Rather than go by a guide, it would be better to do a clip test of a frame or two with the temp that you will be reguarly using, and the dilution that you are used to using. You have to remember something: different developer components react differently to temperature change. For example, under 55 F (about 13 C) hydroquinone ceases to work at all. Metol reacts less to temperature than does hydroquinone. Other developer components react differently. To get a rough estimate, I would use the factor of 1.055 for each Faurenheit degree in change (sorry, in the USA Fahrenheit is king: do your conversions). - David Lyga

Laci Toth · Sep 7, 2019

David Lyga said:
Rather than go by a guide, it would be better to do a clip test of a frame or two with the temp that you will be reguarly using, and the dilution that you are used to using. You have to remember something: different developer components react differently to temperature change. For example, under 55 F (about 13 C) hydroquinone ceases to work at all. Metol reacts less to temperature than does hydroquinone. Other developer components react differently. To get a rough estimate, I would use the factor of 1.055 for each Faurenheit degree in change (sorry, in the USA Fahrenheit is king: do your conversions). - David Lyga

Alright David, thank you, I’ll keep this in mind. Yes, I’ll have to make experiments to find the right solution and to adjust it to the conditions.

Laci Toth · Sep 7, 2019

Laci Toth · Sep 7, 2019

MattKing said:
Murray Minchin is a very long term APUG/Photrio member who lives in Kitimat, BC and had similar concerns with tray temperatures.
As a result, he started one of my favourite APUG threads of all time - about pig fodder heaters!: https://www.photrio.com/forum/threads/sue-weeee.25459/#post-356431
The link in his post doesn't lead anymore to a current product, but the idea of using agricultural supply equipment is a good one.
Piglets apparently need to be kept warm .

=)

Is there a general rule for temperature/time reaction rate when developing/stopping/fixing b&w print

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