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  #1  
Old 9th August 2020, 02:32 PM
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Britman Britman is offline
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Default Chemical temperature consistency

So how do you guys keep your chemical at a consistent temperature?

On my first darkroom session I noted that the chemical temp started to rise to match room temp which was 23°C.
Just how critical is the temperature?

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Old 9th August 2020, 03:03 PM
John King John King is offline
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For B&W paper development not that critical. It is better to be a few degrees over than under. For B&W film development it is essential that you keep the temp +/-1/2 a degree.

For colour you have to be that bit more stringent, in fact fastidiously stringent +/- .5 of a degree or you will waste a lot of paper.
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Old 9th August 2020, 03:27 PM
Mike O'Pray Mike O'Pray is offline
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As your darkroom is your bathroom it will be at the house ambient temperature so for b&w film and paper development you start off with the major advantage of room temp being close to what you will be developing film and paper.

If you have a means of knowing what the bathroom temp is then you can either add hot or cold water to get to that temperature and for the duration of your session the chemical temperatures will remain as near constant as makes no difference.


If it's the summer as now and during one of our heatwaves such as this weekend I'd just get the film developer temperature to the room temp and then check on the temp/time charts such as Ilford provide to work out what changes in time are required for say 23-24 compared to the standard 20.

In the case of a longish printing session the paper developer temp might rise a couple of degrees from that which was the case when you started due to the presence of a human body( yours ) but unless you end up a log way from 20 then I'd not worry about the effect on the print's development

Mike
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Old 9th August 2020, 03:35 PM
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Thanks guys.
Choosing the right time of day is also important for me as the bathroom is west facing and get the sun most of the afternoon.

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Old 9th August 2020, 03:37 PM
Richard Gould Richard Gould is offline
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The temperature for paper is not critical, a few degree's up is not that important, remember we tend to develop to completion, and after and after that point nothing more will happen, with film it is a different story, you must try to keep within 1/2 a degree or so, but the starting point of temp for film developing doesn't matter as long as you adjust the time for the temperature, for instance, normal starting point would be 20, but sometimes this time of the year the water out of the tap can be 25, so adjust the time for the temperature, my normal time in ID11 would be 8 for my film of choice, Fomapan 400, which these days I shot at isl 250,so at 25 |I develop for 5 minutes, which allows for the temperature, and how do I get the different temperature's?, easy go to the Ilford.com website where there is a download pdf of a film developer time/temperature compensation chart, , for fixing and stop the temperature is not crictal, it will fix and stop as well at 18 as at 25,only developer for film is important,I would also add that I use my ID11 as stock, so I check the temperature of the bottle of developer, and adjust my times from there
Richard

Last edited by Richard Gould; 9th August 2020 at 03:42 PM.
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Old 9th August 2020, 03:46 PM
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I do as Mike suggests and dev at the ambient temperature whenever possible (not at the moment - it is 33 degrees outside). Much above 20C however, times can sometimes start to get a bit short for timing accuracy.

Whilst +/- half a degree (and similar timing accuracy and consistent agitation) is something you should certainly aim for in the interest of consistency with B&W film, you will not cause any major problems by being a little outside these constraints. A little extra development will result in slightly more contrasty negatives and conversely, a little less development will result in lower contrast negatives; within reason, this can be compensated for in printing but if you get too sloppy, image quality will suffer and you will get inconsistent results from roll to roll which just adds to the confusion.

Only the developer needs this level of precision and stop and fixer are far less fussy: stop just needs the film/paper in it long enough to neutralise the alkalinity of the developer - typically 10-30 seconds for film and RC paper and fixing time can be extended a bit (say up to 50% or so) without problems (tho with fibre paper you don't want to extend it too far as it makes washing the paper much longer).

Colour, as John says, requires much more stringent time and temperature control at the higher temperature but I have little experience with colour.

Last edited by Bob; 9th August 2020 at 03:57 PM.
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Old 9th August 2020, 04:00 PM
Mike O'Pray Mike O'Pray is offline
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Quote:
Originally Posted by Mike O'Pray View Post
but unless you end up a log way from 20 then I'd not worry about the effect on the print's development

Mike
I once knew an old Canadian lumberjack who in his long career ended up a log way from 20 but in a darkroom the key word is long

Mike
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Old 9th August 2020, 08:55 PM
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Martin Aislabie Martin Aislabie is offline
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As others have said, printing with the chemical temperatures are above 20C is not a problem - we generally develop, stop and fix prints to completion.

So by the chemicals being a little warmer means the reactions happen a little quicker, completion is achieved a little sooner - but no harm done but don't bother trying to adjust your processing times to compensate - just stick to what ever you are using.

Printing when the chemicals are cooler than 20C can lead to problems.

As a typical guide, if the air temperature in your darkroom is 20C, then the chemicals in your print trays would be 18C~ish - which is still OK.

However, if your print developer drops much below 18C, you start to see problems.

I once tried to print in my old temporary darkroom and the noticed I was starting to get very muddy looking prints (low contrast and very poor black density), I noticed the developer was only at around 14C.

Nothing I did seemed to have any real change to the developer temperature, so I had to give up for the day.


Film developing is very different.

Your film developer needs to be 20C +/- 0.5C when you start.

The stop and fix need to be 20C +/- 2C, to stop the film emulsion from cracking (the technically name is reticulation) due to thermal shock.

If your darkroom is cool/cold and you want to develop film, having a washing-up bowl of warm water and putting your measuring cylinders/jugs of working strength stop and fix, is a great way of managing your stop and fix temperatures.

For your film developer temperature control, one shot chemicals is a great way to go.

Measure your film developer temperature and then adjust the addition water temperature needed to make up the working strength developer to achieve 20C when the two are combined. Being one-shot you thrown the developer solution away at the end of the development and start again for the next films.

If your film developing tank (loaded with your to be developed film) is say more than 2C cooler the 20C target temperature - then is can be added to your washing up bowl of water that is keeping the stop and fix at a sensible temperature. However, the film tank needs to be in the warmish water for a while in order to get not only the external wall of the tank but also the films and their reels up to temperature too. Sticking a thermometer in to the tank will tell you its internal temperature.

For what its worth, I adjust my working strength film developer temperature by running warm or cool water on to the outside of its measuring cylinder to get as close to 20.0C as I can.

Films from Ilford, Kodak and Fuji are fairly robust to reticulation but its better to avoid risking it by a little care and attention.

Martin

Last edited by Martin Aislabie; 9th August 2020 at 09:05 PM.
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Old 9th August 2020, 10:13 PM
Mike O'Pray Mike O'Pray is offline
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Not to encourage any slackness, you understand Britman, in your attention to temperature but in terms of the effect of a gap between ambient temp and developer temp I did a "quick and dirty" experiment the last time my darkroom was 27+ degrees C. My tank is kept in the darkroom all the time and as it was about 4:00pm I think it was safe to assume that the tank was at or very close to the ambient temp of 27.

I filled the tank with water at 20 and measured its rise with a Jobo thermometer over the 12 mins required for HP5 in Xtol. By the end of the time the water had risen to about 20.75 so less than a degree

According to a table which Ralph Lambrecht provides in his book I should have reduced the time by less than a minute say maybe 40 secs only.

Had I been developing a film would I have seen an increase in contrast as a result? Probably but not one that could not be coped with in terms of an acceptable print - I do not believe

So my conclusion is that above 20 and unless the ambient temp in the room is getting close to 29-30 which is decidedly uncomfortable for darkroom work - for me anyway, then a few degrees up from 20 in the room temp seems to make surprisingly little difference to the developer temperature over 12 mins.

It certainly suggests that if the darkroom is say 23/24 degrees C then while using developer at the same temp is the "right thing" to do the actual difference it makes to the negative if you were to be satisfied once the developer had got to say 21 or so might be very marginal

I say this as one who probably spends too long in trying to get developer temp spot-on. Usually I add a little too much hot and end up with 20. 8 /21 so then place the whole now-mixed developer in cold water and wait until it has dropped to exactly 20 and probably waste a few minutes doing this which I will never get back .

Mike
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Old 9th August 2020, 10:32 PM
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Thank guys, fantastic information.

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