Maintaining temperature for processing

<p>I live in rural France and as such, pro labs aren't on every street corner, so I process all my own films. I have difficulty maintaining exact temperatures (Particularly important for the first dev) and I'd like to know what other people do to surmount this problem?</p>

<p>I considered a fish-tank heater, but these rarely go higher than 32°C (I need 38°C) <em>presumably to avoid boiling the fish...</em>are there any other options please?</p>

<p>Put your containers in a water bath (larger container with water in it) with the temp of the water at what you want to maintain. You can then add cold or hot water to maintain the water bath temp, thus keeping the chemicals pretty constant temp. If the actual developing tank is also changing temp, then in between agitation, put that tank in the water bath also. If the water bath doesn't do it.....then put the water bath in a larger container yet (or maybe your tub with water in it.) Best however are heaters made specifically for developing film. I forget who makes them, but am sure someone on photo net knows.</p>

<p>Thank you <strong>Thomas</strong> - I think perhaps my water bath is just not large enough, thus the temperature changes faster. This said, it would be nice to have a thermostatically controlled heater...</p>

<p>Only the development stage requires close temperature control. A thermostatic mixer is ideal (a good one costs about $500 in the United States). For occasional use, it is sufficient to use a water bath, which you can mix and temper with hot and cold water. It needs to hold within 1/2 deg C for about 20 minutes. Pre-temper all the chemicals prior to use (checking the water temperature from time - it takes a couple of hours). Immerse the developing tank between agitation - it holds the temperature and rinses away any leaks.</p>

<p>In the old days (20-25C processing), any old dish pan would suffice. At 38 deg C you need something with insulation, and possibly a heater. A picnic cooler works well, is rugged an inexpensive. A small heater can maintain temperature, but takes too long to heat a lot of water. Hand mixing is a far quicker method.</p>

<p>A shallow pan with a slow infusion of tempered water is the safest, cleanest and most effective method. That is the way I worked professionally for years for both film and printing.</p>

If you scan your negatives anyway, you might consider a C41 blix (two-bath) kit. These are said to be inferior to real C41 kits regarding longevity, but they are easier to work with in difficult conditions.

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Temperature only really matters for the first bath with these kits, and even then, it is sufficient to keep the <i>average</i> temperature at 38° instead of trying to achieve the <i>exact</i> temperature. If (by experimentation with hot water) you know that your development tank cools off by 1° during the development time, you simply start with a developer at 38.5° (with the help of your microwave). You will end at 37.5°, but your average development temperature was 38°.

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In fact, the blix kits even work at weird temperatures like 15 or 20°C! They just take a lot longer (10 minutes or more).

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The above does not apply to the original C41 process chemicals of course. These you must handle precisely according to instructions (I presume, due to lack of personal experience).

<p>You should look into laboratory immersion heaters. Companies like Cole-Palmer, Heet-o-matic and others make immersion heaters for just this purpose, thermostatically controlled, and not too expensive. Google laboratory immersion heaters and you will find plenty of options.</p>

<p>Although not cheap, check out nova darkroom in the UK.</p>

<p>Ian,</p>

<p>I am developing C-41 with a home made water bath. I used a plastic dish pan for the container, an aquarium heater for heat, an old waterbed thermostat for control, and a cooler pump for circulation of the water. I disabled the thermostat built into the heater so it is on all the time, and the waterbed thermostat which goes up to 100 degrees F is very precise. I'm sure the thermostat built into the heater would not work because it is above the water level. I made a little platform to hold the developing tank, and the chemical bottles so they don't turn over or move around, as the current from the swirling water is fairly strong. If you don't know what a cooler pump is, here in the southwest, we use evaporative cooling as a cheap way to get our houses a little more comfortable. The pumps are available in any hardware store for about $15. It only takes a few minutes to set up this Rube Goldberg machine, but it works fine. If you try this, be sure to fill the pan with hot water, or you will be waiting a long time for the temperature to come up. Good luck<br>

Best regards,<br>

Chris</p>

<p>Thanks alot everyone - it's given me serious food for thought! I'll check out what's available from my local hardware stores - I'm not worried what it looks like, just that I get even temperatures. (And Chris, thanks for the info on the pumps - it gets warm here too!!)</p>

<p>You can find out a very useful solution here: http://www.kryptosinistographer.com/2008/03/at-home-e-6-pro.html<br>

You can easily modify an aquarium thermometer to the temperature range you are looking to use. Also, you can use a steel tank with a neoprene wrap to insulate well enough to maintain the necessary temperature during development. Lastly, it is an 'average' so if you see a 3 degree temperature drop over the development time, just start 1.5 degrees too high at the beginning and things will work out well.<br>

Good luck!</p>

<p>Very interesting article - many thanks for proposing it here.</p>