Is an infrared thermometer reliable to measure our chemistry temps?

goodimage · Oct 24, 2019

Just wondering. I use the General Mini Infrared IRT 3. Can this technology be trusted?

MattKing · Oct 24, 2019

The ones I've read about aren't precise enough for things like developer.
They could be useful for other parts of the process, where somewhat less accuracy is required.
And you better be careful - some people are really irritated when people refer to developer as "soup"

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goodimage · Oct 24, 2019

Sorry about the Cambells faux paux. My apology to everyone online tonite. Signed a Neewbie.

MattKing · Oct 24, 2019

No apology necessary .

Sirius Glass · Oct 24, 2019

Calling developer "soup" is like calling a person a "muggle", those are pejorative.

Ariston · Oct 24, 2019

Haha, I never knew photographers were so sensitive. You shouldn’t let me find out stuff like this. I already use the term “shooting a photo” because I am too obtuse to be bothered with anything resembling political correctness!

mshchem · Oct 24, 2019

Most IR thermometers I've used should be adjusted for material emissivity. I know stainless will read different than carbon steel. I wouldn't take the chance. I've heard the term "soup" used for chemistry.
I would think properly calibrated IR would work.
For my work I use a Jobo color thermometer, Kodak Process thermometer, and my nice dial thermometers. The Jobo and Kodak thermometers agree given time to reach equilibrium. I've only had to make minor adjustments over the decades to my favorite dial thermometer. I have some digital aquarium thermometers, I bought from an Ebay vendor from China. They are dead on, GIVEN TIME, in agreement with the Kodak. These little digital things have a sensor on a 1 meter wire and are powered by a button cell, LCD readout, around 3 dollars each. There's a thermocouple buried in the plastic of the sensor. Thermocouples are pretty much a quasi Primary standard.

AgX · Oct 25, 2019

I reject terms as "soup" and "shooting"...

Thrermometers:
I would not use a IR-one (actually not even got one.) If you want to save money on a new thermometer and are only doing colour (yes, I know this is a B&W thread), you may use an electronic contact medical thermometer. They are cheap, but very precise, however only meter around 100°F and are a clumsy in practise as they only show a maximum value, so have to be reset before each metering.

msage · Oct 25, 2019

Ariston said:
Haha, I never knew photographers were so sensitive. You shouldn’t let me find out stuff like this. I already use the term “shooting a photo” because I am too obtuse to be bothered with anything resembling political correctness!

It is not being politically correct, it is using the correct words and names. The one that bothers me is calling fixer, hypo!

David Lyga · Oct 25, 2019

I also despise 'soup' and I also despise the very old way of talking about the solution between developer and fixer: 'short-stop'. Where did that come from? 'Hypo' is not only plain incorrect, but obscene, as well. I also hate 'awesome', 'super', and 'Dave'. - David Lyga

MattKing · Oct 25, 2019

I'm tolerant of those who use "hypo", as long as they are actually using old fashioned sodium thiosulfate (historically known as sodium hyposulfate) fixer.
If they are using modern rapid (ammonium thiosulfate based) fixers, I'm unhappy.
And if they start using "hypo" to refer to wash-aid (e.g. Kodak Hypo Clearing Agent) - I rarely forgive!

Sirius Glass · Oct 25, 2019

I still use the term "hypo", but I am not "hyper".

Trask · Oct 25, 2019

No “soup,” even a bit tungue-in-cheek? I recall Donald Qualls’ Super Soup...a bit of fun is no sin.

mrosenlof · Oct 25, 2019

"soup"? irritated? really??? some people need to relax a little bit. I don't think it's a term I use, but it wouldn't offend me.

A few years ago, I bought a steel developing tank somewhere used. It has one of the old 60s/70s Dymo labels that says "HIPPO CLEAR". And since then I've never had a hippo in my darkroom.

Neal · Oct 25, 2019

I have a cheap one and when I point it at a rotating Jobo tank it agrees with the thermometer in the tempering bath.

Mainecoonmaniac · Oct 25, 2019

I have one that I use in my kitchen. I think they're good for surface temperatures like BBQ grills. I don't know about getting the temperature of a whole graduate of developer.

Arklatexian · Oct 25, 2019

goodimage said:
Sorry about the Cambells faux paux. My apology to everyone online tonite. Signed a Neewbie.

Yes, soup makes mighty "weak" developer and developer makes lousy soup. Fixer is much better. Don't try it. That was a joke. A joke, that is.........Regards.

goodimage · Oct 25, 2019

Mainecoonmaniac said:
I have one that I use in my kitchen. I think they're good for surface temperatures like BBQ grills. I don't know about getting the temperature of a whole graduate of developer.

Do you believe that my meter would be accurate if I mixed the solution while taking the temperature with the instrument? That would actually be measuring the solution completely, would it not? Envision this action while aiming the instrument at a tray of solution while rocking it like a normal timed rocking of the tray while developing a print in the tray.

mrosenlof · Oct 25, 2019

I don't know much about those IR non-contact thermometers. I've used a dial thermometer for years of B/W, and it's been good enough. I don't own a densitometer, so your idea of "good enough" might be different than mine.

I recently bought a patterson mercury thermometer that covers a pretty specific darkroom range. It's supposed to be good enough for color work. In my case it was a local sale, so there were no shipping issues.

MattKing · Oct 25, 2019

A 1C or 2F degree of imprecision matters with developer.
At 68F/20C, what do the specifications of your thermometer say about its precision?
I quote: "Measurement Accuracy: ±3.6F (2°C) or 2% of reading (whichever is greater above 32°F)"

goodimage · Oct 25, 2019

Hi Matt. That is from my thermometer manual. Think it is not accurate enough?

MattKing · Oct 25, 2019

goodimage said:
Hi Matt. That is from my thermometer manual. Think it is not accurate enough?

Correct - not accurate enough.
Or more importantly, of uncertain consistency.
If you are aiming for 20C, and your results will range everywhere between 18C and 22C depending on the circumstances, with no way to tell where on that range your particular measurement is, you will have real difficulty obtaining repeatable results with black and white film, and really poor results with colour film.
For chemicals other than developer, and for getting chemicals close to the target temperature, that thermometer might be quick and helpful, but you will want something more accurate and repeatable to fine tune the results.

goodimage · Oct 25, 2019

MattKing said:
Correct - not accurate enough.
Or more importantly, of uncertain consistency.
If you are aiming for 20C, and your results will range everywhere between 18C and 22C depending on the circumstances, with no way to tell where on that range your particular measurement is, you will have real difficulty obtaining repeatable results with black and white film, and really poor results with colour film.
For chemicals other than developer, and for getting chemicals close to the target temperature, that thermometer might be quick and helpful, but you will want something more accurate and repeatable to fine tune the results.

Ok. I will continue to test this thermometer. How do you read a mercury thermometer in a darkroom?

AgX · Oct 25, 2019

By switching on the light.

Unless doing some continuous processing I do not see a reason to take a metering during processing.

MattKing · Oct 26, 2019

goodimage said:
Ok. I will continue to test this thermometer. How do you read a mercury thermometer in a darkroom?

If your thermometer is indeed a mercury thermometer, it must be fairly old!
The problem with the IR thermometers is how they are used. A thermometer that is partially immersed into a solution is more likely to give you a correct reading for the solution.
I have a Kodak process thermometer that I use as a reference standard.
I use inexpensive digital kitchen or multi-purpose digital thermometers. I check them regularly - at or about my target temperature - against my reference standard.

Is an infrared thermometer reliable to measure our chemistry temps?

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