Color grade thermometer

davela · Mar 3, 2014

I am starting to get back into color processing (C41 and E6) and I need a really reliable thermometer for this. I have a $4 glass thermometer that I bought at Freestyle which yields my body temperature to within a degree C and that's been good enough for my black and white work. I also have a fancier Premier Large Dial thermometer, but it disagrees with the glass thermometer by a degree or two (C or F I can't remember). Any way, these thermometers are both a little difficult to calibrate since their range does not cover the ice or boiling water temperatures (standard lab calibrators).

My question: Can anyone recommend a reliable thermometer for color work which I can use for color and to better understand my existing thermometers and derive corrections for them. I don't care if it's metal or glass. There is one being sold by Patterson called the "12-Inch Color Thermometer", priced from about $25-30. I was thinking of this one, but I'd love to hear other users experiences. I know Patterson is a pretty serious company that usually makes good equipment. I have one other related question: does anyone use "aquarium heaters" to warm C41 chemicals. I have an Arista C41 kit that wants the developer held at 102 F, so elevating the temperature of a water heat bath in contact with the various chemical tanks in a thermostatically controlled way seems to be a good approach.

DREW WILEY · Mar 3, 2014

Kodak Process thermometer. Aquarium heaters a bit dicey. Try to acquire a Jobo tempering box or something like that. A true thermoregulator
is better, but expensive.

Tom1956 · Mar 3, 2014

I never cared for dial thermometers. Notoriously inaccurate, IMO.

AgX · Mar 3, 2014

A clinical digital thermomether, is higly calibrated, cheap and often waterproof.

Disadvantages:
-) it holds the maximum measured value
-) to be used with a vague, simple thermometer to temper into the limited range of the clinical one

VPooler · Mar 3, 2014

Body thermometers, mercury ones if possible. Highly accurate and shot tenths of degrees easily. Plus their resolution is between some 35 and 45 degrees, perfect for color processing. I have 4 of them in my darkroom.

jcc · Mar 3, 2014

I use a digital meat thermometer. I stick the probe in the bath or directly into the chem bottles, and have the readout somewhere safe and dry. Cheap, sensitive, responsive, and it works.

Ken Nadvornick · Mar 3, 2014

What Drew said. The Kodak Type 3 Process mercury thermometer. Catalog #106-4955. Highly prized and sought after. Usually around $50, used.

Here's a current offering on the ugly auction site. (I have no affiliation with the seller.)

Short of spending multiple hundreds of dollars on a new calibrated lab-grade instrument, the Type 3 is as good as it gets. I use mine to calibrate all other thermometers in my darkroom, including my Hass Intellifaucet.

[Edit: Added the catalog number from the pictured box for future reference after the above auction ends.]

Ken

BMbikerider · Mar 3, 2014

I have both a mercury thermometer and a Kodak Digital one which I have had for upwards of 20 years. Both correspond with each other with regard to temp readings and I have had no experience of faulty developing of any material so I must presume they are both accurate. A degree or so either way will not make one jot of difference so long as you know that there is a difference., then allow for it. They used to say a colour thermometer had to be accurate to +/- 1/4 degree but this just isn't so as long as you are aware if there is a discrepancy.

John Shriver · Mar 3, 2014

Note that the Kodak Process Thermometer is illegal to ship via USPS -- all that mercury. If your seller does ship it that way, they should be sure it is packed so it doesn't break, and is in several well-sealed plastic bags. If it breaks and drips mercury out a corner of the box, they will be in a whole lot of legal pain…

It's my calibration reference.

benjiboy · Mar 4, 2014

Paterson certified colour thermometer http://www.bhphotovideo.com/c/product/273229-REG/Paterson_PTP363_Certified_Thermometer_9.html

DREW WILEY · Mar 4, 2014

No way a 23 buck thermometer is legitimately certified. Maybe some hokey marketing definition of the term, but don't expect anywhere near the
accuracy of the real deal. Certified thermometers are readily available from actual scientific suppliers in the two to three hundred dollar range.
The Kodak Process thermometer is analogous, but made for the mid-range temps typical of a darkroom, and with a nice suit of stainless armor
to protect from breakage. Type 3 is the best. Sometimes they turn up used reasonably priced. Yes, the main point in any darkroom is simply
consistency, but some processes need better temp control than others and warrant purchasing the real deal.

benjiboy · Mar 4, 2014

DREW WILEY said:
No way a 23 buck thermometer is legitimately certified. Maybe some hokey marketing definition of the term, but don't expect anywhere near the
accuracy of the real deal. Certified thermometers are readily available from actual scientific suppliers in the two to three hundred dollar range.
The Kodak Process thermometer is analogous, but made for the mid-range temps typical of a darkroom, and with a nice suit of stainless armor
to protect from breakage. Type 3 is the best. Sometimes they turn up used reasonably priced. Yes, the main point in any darkroom is simply
consistency, but some processes need better temp control than others and warrant purchasing the real deal.

Paterson are a very old and reputable company, and this thermometer is designed to be suitable for all colour processing and certified to be accurate to +/- 0.14 degrees C. nobody is asking for a sledgehammer to crack a nut.

AgX · Mar 4, 2014

DREW WILEY said:
No way a 23 buck thermometer is legitimately certified. Maybe some hokey marketing definition of the term, but don't expect anywhere near the
accuracy of the real deal. Certified thermometers are readily available from actual scientific suppliers in the two to three hundred dollar range.

Meanwhile there is a worldwide metrological standard for clinical thermometers.
Seemingly the cheapest way to gain high accuracy. Of course with the stated disadvantages of these meters.

jcc · Mar 5, 2014

DREW WILEY said:
No way a 23 buck thermometer is legitimately certified. Maybe some hokey marketing definition of the term, but don't expect anywhere near the
accuracy of the real deal. Certified thermometers are readily available from actual scientific suppliers in the two to three hundred dollar range.
The Kodak Process thermometer is analogous, but made for the mid-range temps typical of a darkroom, and with a nice suit of stainless armor
to protect from breakage. Type 3 is the best. Sometimes they turn up used reasonably priced. Yes, the main point in any darkroom is simply
consistency, but some processes need better temp control than others and warrant purchasing the real deal.

Certified to what standard? My lab (science, not photo) uses $30 thermocouples from National Instruments (a scientific supplier), sampled at 50k per secondthey're accurate, precise, highly sensitive... and cheap! Spending hundreds of dollars for a thermometer is just throwing away money, IMHO, but my opinion doesn't really matter as long as it's not my money.

DREW WILEY · Mar 5, 2014

Try making a matched set of color separation negs with one of those cheapie thermometers. The real deal is worth every penny. Up until last yr
when the bldg got leveled for some expensive condos, there was a scientific supplier about four blocks away that sold nothing but thermometers for decade, mostly glass, and mostly expensive. Not a small inventory either. Let's see.... with biotech firms and
pharmaceutical firms on almost every block around here, and UCB right up the street, somebody musta had a reason to keep him in business...

davela · Mar 10, 2014

Thanks to all posters for the informative suggestions. A lot of opinion seems leaning towards the Kodak process thermometer which has the interesting feature of being calibrated at specific temperatures of prime interest to darkroom work and not exceedingly expensive. A high-grade lab thermometer might be in the future as an additional reference, and I might try the Paterson Color thermometer too (what's to lose at that price). That Jobo tempering box is awfully interesting - I see them on the used market at not ridiculously high prices, so it might be in my future as well. In the meanwhile I'll arm myself with improved thermometers and use manually controlled heat baths and chase the right temperatures to get started. I'll post some examples soon I hope.

mts · Mar 12, 2014

note that most quality dial thermometers can be calibrated to read properly in the temperature range you need to measure. I have a dial thermometer that I use for color processing; calibrated with my 50-year-old Kodak color thermometer. Usually there is a small nut that can be turned to adjust the dial unit's reading. I keep the glass thermometer stored safely and use the dial to measure solutions in the sink.

johara · Mar 12, 2014

Agreed with AgX and others that electronic or other medical ("fever") thermometers are very useful for calibrating a dial
thermometer for use in 100 deg. F color processes like C41. If you put your dial thermometer and (one or more, I used
3 to be sure) medical thermometers into an insulated water bath at close to 100 deg. F, let them sit for a while, and take
the reading, you'll get the right temperature even from a peak reading instrument (because it's not changing much). You
can then adjust and use the dial thermometer that day and not worry about it being off.

For B/W I calibrate the dial device against a Paterson alcohol thermometer that is tested at 68 deg. F.

mklw1954 · Mar 25, 2014

I use the Paterson Colour Thermometer with good results.

I determine the corresponding temperature on a digital LCD thermometer with a wire probe (Extech TM20) and use the digital thermometer. Using a pot of water at the target temperature, 20C on the color thermometer is 20.7 on the digital and 39C (for color film developing) is 39.6C on the digital. Calibrate periodically.

DREW WILEY · Mar 25, 2014

Unless you're doing research and needing to communicate hard standards, the most important thing with any thermometer is repeatability, followed by ease of use and reading. I gave up on digital thermometers because of their relatively slow response, and am not aware of any
dial thermometer I'd consider accurate enough for critical color use. Some process standards are much fussier than others. I just don't like second guessing, so am happy with my Type 3 Kodak process thermometer.

Color grade thermometer

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