Managing temperature for tray development

[Fatih Ayoglu]

Hi,

My darkroom is around 18-19 degrees and I’d like to keep my trays at 20C while im developing sheet films. I have the tray heater already but my trays are plastic ones.

Do you recommend me getting an enamel tray, which is still getting sold or the ones like stainless steel ones that they use to in food industry?

Many thanks,
Fatih

 

[koraks]

I'd not bother with it and just develop a tad longer if it's a little cooler.

I'd not use anything metal/stainless since photochemistry may still make it rust. You can limit this by religiously cleaning and drying everything, but I'd personally not go there. Just use the heater with your plastic trays; it'll be slightly less efficient but it'll still work OK. Or just forget about the heater altogether...

 

[mshchem]

I have an oil filled electric radiator I use in the cooler months holds 20°C nicely.

 

[MurrayMinchin]

I use waterproof electric seedling heat mats for raising tray temperatures in my c-c-cold darkroom, but I've heard that thermostatically controlled baby pig heat mats are what all the cool cats use.

 

[Fatih Ayoglu]

I have an oil filled electric radiator I use in the cooler months holds 20°C nicely.

Oh I have a radiator there, which is smart and I can control it remotely. Just lazy with adjusting it and with the enlarger, the temperature gets sometimes to 22-23 which is too much for me

 

[Paul Howell]

Depending on the film, say for sake of example TRix pro, D76 stock at 12 minutes at 20 degrees (C) at 18 degrees according to my trusted 1964 Kodak data guide for 18 degrees add 2 minutes, at 19 add one minute. If much lower than 17 I would use a heater of some sort. If you have a darkroom sink with running hot and cold water get a temperature control valve and use SS trays.

 

[Fatih Ayoglu]

To be honest, I’m trying to develop sheet films to create masks for Bw or C41 printing. They require not so standard developers, like for BW masks I use 1+200 Ilford PQ on Arista Ortho film and for C41 masks I use FP4 with Muir Softshot. For normal tank process, I always extend the dev times accordingly but for masks I’d like to build a standard to make sure everything stay same.

I have a temperature control valve set for 40C color film pre warming, maybe I can use that by adjusting the temperature and creating a water bath for the teay

 

[DREW WILEY]

Hi again. I strongly recommend a stainless steel developing tray since that material conducts temperature quite efficiently. Any type 300 stainless, especially 316, will be suitable for all routine darkroom chemicals. It won't rust. Glue some brass pipe caps onto the bottom of this to act as support feet. Then you put the whole thing in a larger thick plastic tray which acts as a tempering bath holding warmer water. Plastic is the better thermal insulator in this case. You can add a drip line if needed into this bigger surrounding bath to keep it warm. Then add an acrylic plastic lid for your stainless tray to keep temp until its time for actual usage.

Of course, it also helps to have a passive radiator-style room heater to keep ambient air temperature close if needed.

I have various gadgets to maintain correct temp, including a very precise thermoregulator which will maintain temps to within 1/10 deg F. But it's energy intensive and overkill for basic masking work. So I just use a water jacket as described plus a Zone VI compensating tray thermometer probe, which automatically adjusts time relative to minor temperature shifts. Those can take some patience to find, but do turn up from time to time.

Masks develop fast because you are after something low contrast. So you could also try a "drift-by" approach, starting out around 21C and ending up around 19C.

 

[Doremus Scudder]

I like the water-bath idea too for immediate use. While a stainless-steel tray will conduct heat better than plastic, plastic trays will work too, as long as you give them time to come to temperature. If you go the stainless route, be sure to get good-quality stainless steel like Drew advises. Cheap stainless will rust.

When I developed film in a colder than 20°C darkroom, I'd just mix the developer at the right temperature, i.e., 20°C and then use it right away, with the developer tray in a larger tray of freshly-tempered 20°C water. The amount of temperature drop during the developing time was negligible. I used plastic trays for both. This works well if you develop what you need within a short time, before the temperature has a chance to drift much. Larger volumes drift more slowly.

The other approach would be to simply develop at ambient temperature, using the Ilford time/temperature conversion chart to adjust the developing time as needed for whatever the ambient temperature is. That would still enable you to use a "standard" time, and adjust it as needed for temperature. This would be the more-pracitcal approach if you had a tray of developer that needed to stay out for a long time. Simpler than a running-water bath that would need to be fed with a tempered water source to stay at correct temperature for long periods. While a tempering bath will hold fairly constant for some minutes, it won't hold temperature for long periods of time. You'd need to replenish it with the right temperature water regularly or have a tempered feed, both of which seem troublesome to me.

Best,

Doremus

 

[DREW WILEY]

A good analogy is stainless kitchen sinks. The cheapo home center variety will show tarnish if you leave lemon juice or ketchup on it for half an hour. Then there are commercial grade ones highly resistant to food impact, as well as marine grade stainless resistant to saltwater corrosion. Then there's lab grade - typically Type 316 stainless when it comes to darkroom items; that's what you want.

In my tray pile I have a number of big stainless trays which were used in the dye transfer printing industry for decades, and show no signs of corrosion at all. Same with my smaller film trays.