Thermometers

[Lenny Eiger]

Glass thermometers aren't what they seem to be. They can all be inaccurate, including the Kodak ones. I had one of the expensive ones, and it was many degrees off. I finally got a real scientific thermometer that I could depend on. Truth is, all glass, and scientific, etc., are very good at being repeatable. That's what matters.

They aren't good at being accurate. They can be as much as 6 degrees off. That's quite a bit, in photographic terms. The less expensive digital ones are calibrated at "points" which means 0 degrees C and 100 degrees C, which is useless to photographers, for the most part.

If you are interested in accuracy, you need to get something made for a science lab... there are plenty around, $100-$500.

Lenny

[Hans Berkhout]

If you decide to use a glass one keep in mind that you will break it sooner or later. So always have an identical back-up one and make note how it's reading will differ from the one you are (or have been) using.

[John Olsen]

I have five thermometers, which I've tested versus my baseline Weston. The comparisons are stored in my notebook, so if I suspect the Weston is going haywire I can do a cross check. I learned my lesson when a different thermometer went belly-up a few years ago.

[Eric Woodbury]

The Raytek specs are bad. +/- 3.5 degrees and repeatability a tenth worse. IR depends on emissivity first, followed by a host of other variables. I use a mercury tube type from a chem lab. Certainly it is repeatable. Then calibrate yourself to this and call it good. Doesn't really matter after that. And what's a degree here or there?

[Drew Wiley]

I standardize on just one really good thermometer. It's a Kodak Process Thermometer Type 3. Faster to use and more reliable than any electronic thermometer I've
owned. Very accurate CERTIFIED thermometers are still readily available from scientific supply houses. The trick is to find a model optimized for the temperature
ranges typical of darkroom work. Expect to pay two or three hundred dollars. But used Kodak ones often turn up at lower prices. There were themselves expensive
new, of course. The most important thing besides the repeatability of a given instrument is simply to stick with it, as your personal standard. For fussy work like
color separation negatives I like to keep process temps within 1/10 degree F. That requires an expensive thermoregulator for the water bath. No mixing valve or
immersion heater has anywhere near that kind of accuracy. But for ordinary work it's sheer overkill, and a simple passive water jacket is sufficient, or in the case
of something like RA4 paper development, a basic Jobo tempering box for keeping the chemical flasks within parameters.

[ROL]

You'll have to pry the Zone VI Compensating Developing Timer out of my cold, dead hands. Using it, and only it, I can calibrate all my times and be consistent. Works for me.

Otherwise, a cheap thermometer for measuring wash temperature and such is way close enough for photography.

Well, if my CSI–sense serves, at least we will know accurately your time of death!

I love mine as well, but never thought about how to calibrate my other thermometers with it. Yeah, for most B/W procedures, I'm good to within 1ºC or so – I love B/W.

[Drew Wiley]

I use that Zone VI goodie routinely for black and white paper developing or garden-variety drift-by water jacket monitoring around sheet film trays. I would love to
have a spare. Not really suitable for critical sensitometry; but 90% of what one does in a darkroom is not that.

[photonsoup]

I finally found a solution that I find acceptable to me. I ordered this thermistor, and a Legacy Pro adjustable dial thermometer from Freestyle. The thermistor is accurate to plus/minus one quarter degree C.

Comparing the Paterson to this show the Paterson to be fairly close but very slow to react (it is in a protective clear tube).

[Ginette]

...
Comparing the Paterson to this show the Paterson to be fairly close but very slow to react (it is in a protective clear tube).

Protective tube is for storing, not to be used with.

[Ginette]

... Kodak Process Thermometer (there are color versions for 75F processing and B//W at 68F)

How can we distinct theses 2 versions?
I have 3 Kodak Process Type 3.