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Old 28th April 2011, 09:22 PM
Mike O'Pray Mike O'Pray is offline
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Default Maintaining process temp during hotspells

In, I think, most regions in England last weekend we went through an unseasonably hot spell and the issue of process temp reared its head. Well it did in my darkroom where ambient temp went to 27/28C. Of course the high temps have now gone and may not return until the next and last hotspell of the year( probably last 2 days in August followed by a thunderstorm )

Anyway for what it is worth I thought I'd use water as a test for how long it would hold at 20C as I had a film to develop and here is my finding which surprised me.

Despite the room temp of 27C the water in the dev tank held at 20C for the 11 mins I needed.

I felt safe proceeding with dev at my usual dev temp and the negs were fine.

It might not be a revelation to others who have already done this test but it was to me. I had expected a rise in temp and need to take action so creating "fuss and bother" which I like to avoid.

Clearly very long dev times might create issues but for those previously worried about the effect of higher temps and attempting to develop at 20c then my experience suggests that room temp has less effect on dev temp than I had expected for normal dev times.

My "thought for the day" as they say on the radio.

Mike
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Old 28th April 2011, 09:32 PM
Richard Gould Richard Gould is offline
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Last week the water out of the tap was 22 to 23, the first film I processed at the temp I developed at 15 mins instead of the usual 17, and checked the temp at and the end,it had stayed at 22, and the film was fine, second film, couple of days later, again water temp of 22/23, developed the film for normal time, 17 min, and the film again fine, slightly better, so how much does the temp of the chemicals have on the film ?, my experiment last week does seem to show that 2 or 3 degrees make very little difference to the result, so in future I won't worry about the temp going a bit above the 20,
Richard
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Old 28th April 2011, 09:47 PM
Neil Smith Neil Smith is offline
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I recently bought a water jug that has a removable plastic tube in the lid that is full of liquid, the idea is to freeze the tube which then keeps the liquid in the jug chilled by being immersed in the liquid. I bought it with the hot weather in mind, but as yet I haven't needed it as the insulation in my shed has kept the temperature very close to 20 but it will come in handy if the weather gets much hotter in the height of summer


Neil
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Old 28th April 2011, 11:53 PM
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Argentum Argentum is offline
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Plastic tank? This is one reason why plastic development tanks are better than stainless steel. Plastic is a poor thermal conductor.
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Old 29th April 2011, 06:03 AM
Luis Luis is offline
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Quote:
Originally Posted by Argentum View Post
Plastic tank? This is one reason why plastic development tanks are better than stainless steel.
It depends what you're counting or hoping for. Plastic will crack, will accumulate dirt or stains more easily, will be more difficult to wash, will dry slowly, once the lid gets loose it won't fit again... said that, I use plastic more often than steel

Summers here are pretty hot, often sustain 40-42 C for a couple of days and that happens several times, 30s are common, and tanks will not take heat as easily as they will loose it, so I won't care much about a 5 degrees deviation in room temperature unless pipes are exposed to sun or superficially buried, which will raise the tap water temp.
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Old 29th April 2011, 06:29 AM
Tony Marlow Tony Marlow is offline
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A blatant plug for Peter Hogan, use Prescysol and process at 24deg.C or get Richard Ross's high tec. processor which automatically adjusts the time as the temperature changes.

Tony
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Old 6th August 2011, 08:50 PM
GeorgeH GeorgeH is offline
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Quote:
Originally Posted by Richard Gould View Post
Last week the water out of the tap was 22 to 23, the first film I processed at the temp I developed at 15 mins instead of the usual 17, and checked the temp at and the end,it had stayed at 22, and the film was fine, second film, couple of days later, again water temp of 22/23, developed the film for normal time, 17 min, and the film again fine, slightly better, so how much does the temp of the chemicals have on the film ?, my experiment last week does seem to show that 2 or 3 degrees make very little difference to the result, so in future I won't worry about the temp going a bit above the 20,
Richard
I seem to recall from college chemistry courses that chemical reactions typically double in speed for each 10C rise. Here's a time/temp chart from Ilford courtesy of Digital Truth. Could be a good thing to keep in the darkroom.

http://www.digitaltruth.com/devchart.php?doc=timetemp

It look as though the plus 10C doubling speed, or halving time, is roughly correct. YMVV.

Cheers, but not with Metol.
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Old 6th August 2011, 09:09 PM
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Martin Aislabie Martin Aislabie is offline
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I find a large tempering bath of water to be very effective - for the sort of temperatures we experience in the UK at least.

The water temperature in an open tray will always be a few degrees (3~4C typically) below ambient air temperature due to evaporative losses.

If the tap water gets above 20C, I load up the fridge with water in plenty of time to get it reasonably chilled

Martin
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Old 6th August 2011, 09:14 PM
Mike O'Pray Mike O'Pray is offline
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Not strictly germaine to the thread but seeing another post today caused me to read the thread again from the start.

Conclusion: What an incredible April it was! The week just ended was damned hot but it never got beyond 27/28 in the darkroom. In fact I think it stopped at about 26.5 in mine and this is August!!

Apologies to you Texans and friends from the Iberian Peninsula who are wondering what the fuss is about but it's a "Brit" thing to obsess about weather matters and even mildly hot weather


Mike
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Old 6th August 2011, 11:57 PM
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David Brown David Brown is offline
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Quote:
Originally Posted by Mike O'Pray View Post
Apologies to you Texans ...
Yes. Temps in the 40s (C) here for weeks!!
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