I'm interested in a controlled, predictable method for lowering fluid to a target temperature. My situation is this: I have a very minimal B&W darkroom setup with no dedicated sink (other than the kitchen sink which does double duty for food preparation). I want all my film processing chemicals and wash water to be the same temperature.

Currently, I fill several gallon jugs with water and allow them to sit overnight on the darkroom (a.k.a. converted walk-in closet) floor along with the bottles of fixer and developer concentrate. When I'm ready to develop film, all the chemicals are the same room-temperature. This works fine when room temp is less than 75 degrees, but my not-airconditioned apartment will soon be warmer than 75 degrees, and film processing times with Pyrocat-hd 1:1:100 get awefully short at > 75deg.

So, I'd like to use my freezer to lower the temperature of my fixer and distilled water jugs to match the water that comes from the tap, which in my experience tends to be about 65 - 75deg during the summer months in my locality. What I am hoping for is a formula, spreadsheet, or table that allows me to plug in the volume of liquid, starting temperature, and the ambient temperature of my freezer with the result of the calculation being how long before the liquid reaches a target temperature.

I've scoured Google and www.photo.net/search for any clues and haven't found what I'm looking for. Any tips or help would be appreciated!