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What thermometer are you using? "Photo grade?"

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Get a Kodak Mercury Type 3 if you can find one. Deadly accurate and does not have the typical quirks of digital stuff.
 
I use an extech digital with a 10 inch solid stainless thermocouple. It has 2 leads and can record temp over time
 
I recommend a Kodak Type 3 process thermometer. Its a Big Boy but you will get use to it. The one you mentioned is only accurate + or - 1 degree. The Type 3 process thermometer is accurate to 1/4 of a degree.
 
The only real requirement of a thermometer for B&W is that it is consistent and that you have a matched back-up. Sometimes, a digital one can be a pain in the a!!! Back in the 1990s my firm was given a free digital thermometer by Ilford. However, having spent needless time adjusting the water from 19.9C to 20.1C, and backwards, etc we soon went back to an old fashioned one - simply a case of having that level of accuracy was too tempting to get things exact.

Many years ago I bought three identical budget priced photographic thermometers. Mixed up some water at 20C (using one) and then put the others in. After 5 minutes I then marked each one as follows: First one used to mix the water was at 20C and I marked this with a permanent marker. Second one was showing 19.5C and the other 20.5C. All were marked so that, if one was broken I would know that my chemicals would still be at the same temperature )i.e having done all my tests with thermometer number one, if it broke I knew that I should mix to 19.5C when using the first back-up thermometer. However, up till now I am still on the first thermometer.

David.
www.dsallen.de
 
I have an Omega dial-clip style. I don't know how accurate it really is, but it's consistent.

In actual fact, I often don't use one - I use distilled water at room temperature, (here in Prince George the tap water is so mineralized that I'll only use it for wash water), and just check my digital clock/room unit for the room temperature where I keep my chemistry, and adjust accordingly. My kitchen, where I do my film, is usually around 68-70, I use highly dilute Rodinal or HC110, and strive for longish, say 11 to 15 minutes development time, so I don't think I suffer too badly from my innate sloppiness.
 
Jim17x said:
I recommend a Kodak Type 3 process thermometer. Its a Big Boy but you will get use to it. The one you mentioned is only accurate + or - 1 degree. The Type 3 process thermometer is accurate to 1/4 of a degree.
Click to expand...

I use my process thermometer to regularly check the accuracy of a couple of cheap kitchen digital thermometers - the ones with probes at the end of a cable.

I also do all my developing at room temperature in replenished developer, adjusting the time to match the temperature.

This works fine for black and white.

For colour, I would buy one or more of the digital thermometers used for measuring the body temperature of children (the quick response ones), and do the same accuracy check.

I prefer to use a more "disposable" thermometer when I'm in the midst of a developing session - if I drop or damage one of the cheap digital ones it is a disappointment, whereas if I drop or damage my Kodak Process thermometer ...
 
I have a few of them, but the one I usually use is a digital one made by, a company called testo-term, model #1103, "Made in West Germany." I'm guessing it dates from the 1980s. I haven't had to recalibrate it since I got it a few years ago, I think from Ann in the APUG classifieds, and it gives quick readings with a digital readout, and can be set to Farenheit or Celsius. I don't think I've changed the batteries in all that time either.
 
What thermometer are you using?

My darkroom standard is also a Kodak Type 3 Mercury instrument. Got mine from Bob Shanebrook here on APUG. I disassembled, cleaned, polished, and remounted it in its stainless steel sheath. It now hangs in a (very secure) location above the sink and is used only to check the calibration on my day-to-day adjustable thermometers.

I understand the desire for better readability. Modern digital instruments offer this. But I'm old fashioned enough to want to still calibrate those against a single physical standard. As convenient as they are, digital thermometers are electronic hardware/software beasts that can and sometimes will drift over time. But the coefficient of expansion of elemental mercury never changes.

Because of this, I even maintain an offset calibration factor for my Hass Intellifaucet based on the Kodak mercury standard. Even though the electronic Intellifaucet is four-figures expensive and traceable to NIST standards, it still does not exactly match the mercury instrument.

In fact, they differ by exactly one degree F at 68F/20C, which does sometimes makes me wonder if the Hass was not inadvertently mis-calibrated when it originally left the factory.

[Edit: Thinking more about it, probably not, as the calibration set points would have been in degrees Celsius, not Fahrenheit...]

Ken
 
Last edited by a moderator:
Never owned two thermometers that gave identical readings. Never. Tried a few digital kitchen types (crappy cords, failures), a few glass mercury types (all gave different readings), and finally a Weston-style that is adjustable. Which worked great, except "waterproof" does not mean "submersible," and once water got in the dial, it never came out. I even had a Fisher Scientific model that is used for maintaining the temperature of immunizations. That was wildly erratic. It appears to me that temperature can be measured with a high degree of accuracy, except for 20-25c. That is the black hole of accurate temperature measurement.

So now I use some cheap glass kodak thermometer, it's slow and probably inaccurate, but that's my story and I'm sticking to it.
 
Kodak type 2 lab thermometer. A couple years back, before the Kodak type 2, I bought some darkroom stuff and in the box was an Omega digital with a probe on a nice coiled cord. I checked it against a pretty good thermometer I had at the time and it seem to be very close. I mounted it on my wall by the sink and really liked how handy it was with a nice red led display. About 8 or 9 mos. later I started having some problems with film density and had to start cutting back a little on development. Worked for about two sessions and problems again. I pulled hair and went through about three 24 exp rolls from my bulk 35mm master before I figured out the stupid digital thermometer was the problem. It was handy, but I said never again. I went back to my old thermometer and then I ran into the Kodak type 2 in an antique mall. It went home with me and for $5.00 was some of the best money I've spent. JohnW
 
David Allen said:
The only real requirement of a thermometer for B&W is that it is consistent and that you have a matched back-up. Sometimes, a digital one can be a pain in the a!!! Back in the 1990s my firm was given a free digital thermometer by Ilford. However, having spent needless time adjusting the water from 19.9C to 20.1C, and backwards, etc we soon went back to an old fashioned one - simply a case of having that level of accuracy was too tempting to get things exact.

Many years ago I bought three identical budget priced photographic thermometers. Mixed up some water at 20C (using one) and then put the others in. After 5 minutes I then marked each one as follows: First one used to mix the water was at 20C and I marked this with a permanent marker. Second one was showing 19.5C and the other 20.5C. All were marked so that, if one was broken I would know that my chemicals would still be at the same temperature )i.e having done all my tests with thermometer number one, if it broke I knew that I should mix to 19.5C when using the first back-up thermometer. However, up till now I am still on the first thermometer.

David.
www.dsallen.de
Click to expand...

very interesting.I did something very similar;I bought 5 economy mercury thermometers, left them on the darkroom counter top for an hour, read the temps, calculated their average and picked the one ,qhich was closes to that average.I still use it todayand my R&HDesignsdigital stick was calibrated to itas a back-up:wink::wink:
 
I use a lab grade mercury thermometer to calibrate my other thermometers. Nowadays you will probably have to make do with an alcohol one. They are of sufficient accuracy for darkroom work and are available from scientific supply houses.
 
dial

Well, I guess I have a dial-clip. It says "thermometer, photography and utility" whatever that means. Got it in a box of photo junque. Works for me.
 
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