So my thermometer is off [rant]

I was taught to run a test when changing a part of the process, a new thermometer certainly qualifies!

Mention was made about the Kodak Process Thermometer, Type 3. There is also the older and slightly less precise Type 2. The problems with acquiring any of these is that they have not been made in a long time and can not ship by mail. I bought a Type 3 and a Paterson Mercury Thermometer and in spite of my cautioning the seller both arrived by mail (sigh). One had a separation in the mercury column I fixed it by chilling it enough the whole column of mercury collapsed into the bulb. (i won't go into the process here.) Both work fine now and accurate to each other. I use them as checks on my dial thermometers at school. Good dial thermometers have an adjusting "nut" on the back so with a little nut on nut action [joke] I can recalibrate the dial thermometers. Note that it is more important to be consistent, and use consistent tools, than Bureau of Standards accurate. If you cannot find a good lab thermometer for your check instrument get a drug store fever thermometer, surprisingly accurate over a very short range (easier to make an accurate thermometer over a short range than a long range).

faberryman said:

Buy a good thermometer?

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Good advice! Now which are some " good, accurate thermometers? Kodak Process thermometers mabe? Should one of these be stored vertically so gravity would help keep it accurate? Would ANY mercury thermometer benefit from storing vertically? Also are they naturally more accurate? I am about to buy a thermometer to check the thermometers that I now own (dial, alcohol;, mercury) against. I have read about problems with the Kodak Procrss. Is there a consensus about that piece of lab equipment yet?........Regards!

mooseontheloose said:

FWIW, I had a similar issue too - I had a thermometer that was reading almost two degrees too cold, which of course led to underdeveloped negs. It took a while for me to figure out the problem. I now use a thermometer meant for colour processing and I’m much happier with my results. I test and develop according to that thermometer only, which has helped me a lot.

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are you sure? If your thermometer read too cold, you must have developed toward and therefore underdevelopment is unlikely!

Omega.com sells a nice precision thermometer for under $100.

I am still using a Kodak Digital thermometer which I bought way back around 1992 when I started colour printing. It has proved to be accurate although it is getting a little slow to settle down once it is in liquid. I also have a certified mercury thermometer, not quite so old but when the two are tested together in the same liquid, the difference between them is to small to be the slightest bit significant. I also have a dial analogue thermometer which is 1 degree C out when compared to the other two right through the scale, so I can compensate for the difference and think I can be reasonably confidant using any of them.

RalphLambrecht said:

are you sure? If your thermometer read too cold, you must have developed toward and therefore underdevelopment is unlikely!

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I took it that the thermometer was (for example) reading 20C but in reality, the developer (for example) was really 15C - hence underdeveloped. Is this what you meant Rachelle?

I bought a Paterson Colour Thermometer for $27 when I started doing color and calibrate all my thermometers (digital with wire probes) to it, i.e., record the readings on the other thermometers when the Paterson reaches the target temperature(s). I do this simply by heating and cooling a large pot of water, stopping at the target temperature. It's kind of crude, but take a few readings for each target temperature and it works. The small cost and effort has been well worth it as color film and RA4 prints come out great and it has improved b&w film development as well.

Sorry to hear your thermometer was off but I'm not quite sure what the point is. I have many antique thermometers (and barometers) some of them using temperature scales no longer in modern use e.g Rèamur. Generally if the are "off" for a narrow range you can compensate for this and you did alter your development times accordingly. If you carried on using this thermometer it does not matter what the actual reading was providing you achieved satisfactory results at a particular reading.