Increase in dev. temperatur while developing?

[martin s]

I just bought a digital thermometer (after the 3rd glass one broke) and for the first time I checked on the developer temperature while developing. It was exactly 20,0° C when I started, and steadily increased up to 22.5 °C until the film was developed (10 minutes). It's a pretty obvious thing, since the room has 25-27°C. How should I compensate for this? Average things out, and decrease time (simply assume it's 21°C)? Or should I start at 19°C? I can't relocate to the basement, this room is the only one I have at the moment.

martin

 

[Roger Hicks]

With E6 I use a 'fly by' technique, but with BW, a water bath is all you need. A sufficient mass of water (say 3-5 l) in a bucket or washing-up bowl will not drift significantly in the time available. If it does, just add another ice-cube...

Also consider developing at 24C/75F.

Cheers,

R.

 

[martin s]

Hey Roger, thanks! Good idea with the bucket. Why 24°C? Any advantages, or simply cause of the room temperature? And - do you find those time-conversion tables for increased and decreased temperature useful? Do they work?

martin

 

[Turtle]

another option is to put the water you will be using in bottles and let them come up/down to room temperature before use. That works if you can control room temperature to within the usable range. I do this, aiming for about 19-20 degs c in winter and 22-23 in summer.

 

[Roger Hicks]

Hey Roger, thanks! Good idea with the bucket. Why 24°C? Any advantages, or simply cause of the room temperature? And - do you find those time-conversion tables for increased and decreased temperature useful? Do they work?

martin

Dear Martin,

You're welcome. It's hardly a new idea. Someone gave me that tip in '66 when I started developing my own film in Bermuda...

Yes, 24 just 'cause it's a warm room.

Yes, the time/temperature tables work well BUT they vary from developer to developer (so use the manufacturers' ratios, not generic) AND it's as well to stay in the range 18 -25C. Anything under 18 and dev times can get very long, together with differential slowing of the developer ingredients and effects on tonality; above 25, times get very short and above 30 the film can be unduly tenderized (though most modern films are very tough).

Cheers,

R.

 

[Al Kaplan]

You also need a good conventional thermometer. Dial types can get out of whack. The nut under the dial can be turned to match up with the other thermometer.

 

[martin s]

I appreciate all the hints. I bought one to measure wine temperature with, it seems to react to even minor changes in temperature. It looks like one of those used to poke meat to figure out if it's through.

martin

 

[Turtle]

Always keep a control thermometer as well. This way you will be able to compare any new thermometers against the control. Otherwise, you could be usingn a thermometer reading a degree low and buy a new one that reads a degree high and wonder why your times have gone adrift.

My control and current thermometer agree perfectly so thats easy!

buckets and waterbaths are a great bet but they take some (minor preparation). One advantage of the water bottles/bowser/container method is that the water used for all your solutions will automaticall be at room temperature and teh same temperature regardless. If you work from 19-23 degs its easy to compensate for the temp shifts with dev time. That is admittedly the downside compared to ensuring everything is the same temp each time.