harald
Today I set up a few test samples (just plain water, of course) in bowls of various sizes in my new lab, all at 20°C, and measured how quickly they cooled down.
Result: at an air temperature of 21°C, the water cooled by 2°C in 2 hours.
That’s certainly not dramatic, but what’s the best way to keep them at a consistent temperature?
(It’s also worth noting that the air temperature isn’t always constant.)
Regards, Harald.
WolfgangMoersch
Result: at an air temperature of 21°C, the solutions cooled by 2°C in 2 hours
It doesn’t make any difference at all to the (SW) positive process as long as the temperature doesn’t drop significantly below 18 degrees. Constant fluctuations caused by heating and cooling prevent reproducible results.
Gast
Hello,
If you want to run the S-W process (20°C) at a room temperature of 21°C, cooling shouldn’t be a problem.
As far as I know, the tanks shouldn’t get any colder than the ambient temperature, or am I mistaken?
It’s a different story at 10°C, as it is in my darkroom at the moment. I simply placed the developer in a larger tray, into which I kept adding a bit of hot water from the kettle.
It worked quite well.
Does anyone know how it works with the fixer (TT Superfix Plus)?
Next time, I’ll definitely preheat it.
Regards, Jakob
cfb_de
Hi everyone,
Harald has now posted more accurate temperature readings on the Parallel forum. The wall where his dishes are to be placed was 16°C.
That’s too low for a proper SW process and explains the cooling quite well. This sparked a discussion about heating options for photo dishes, which was both amusing and informative.
And yes, a solution can certainly cool down to below ambient temperature. It’s quite simple – think: clay wine coolers.
Best regards,
Franz
Gast
Hello,
I used to have the same problem. I then came across some small electric heating pads in the supermarket (50W, approx. 30×40 cm, costing 20 DM at the time), which were switchable and had a 3-position switch (off, 1 and 2). I use these to keep my photo trays (developer and fixer) at the right temperature; in other words, if the temperature drops below 19°C, I switch them on – setting 1 is enough – and after about 10 minutes (the time depends on the amount of liquid and the room temperature), the temperature reaches 21°C and you can carry on.
Setting 2 is for the impatient; it allows you to heat the developer up to 25°C in a relatively short time (1 to 25 minutes depending on room temperature and the amount of liquid). Baryta paper is then fully developed within 60 seconds despite using a sparing dilution (Neutol NE 1+11).
As the blankets are washable (plastic cover) but not 100% waterproof, I place the electric blankets in a large plastic bag (blue bin bag) to protect against water ingress (electricity!!). This is sufficient to prevent splash water from getting in. But be warned, as always, Murphy’s Law applies: anything that can go wrong will go wrong. Therefore, the utmost caution is required; in the event of a major flood, you should be able to switch the blankets off at an easily accessible switch.
Reproduce at your own risk and only for people who cannot afford or do not want to buy an expensive electric blanket.
Best regards
Heinz
Gast
There are continuously adjustable beaker warmers (heating plates on which to place laboratory beakers) for beaker temperature control. Compared to the electric blanket solution, these have the advantage that they have been designed for this specific purpose and are suitably fused.
It is also possible to build your own setup using a larger beaker for a water bath with a heating coil from an aquarium shop – instructions are available online if needed.
Best regards
Holger
