Thermometer

jp80874 · Sep 24, 2007

I wandered into the University Photo 1 lab the other morning looking for my friend the teacher. I was reminded of one of her first lessons. There was a two liter pitcher of water in the sink with ten thermometers in the water. The temperatures covered a range of six degrees F.

I like the above line that a man with one thermometer knows the temperature. I use a metal 2.5” dial read out with an 8” metal probe. http://www.bhphotovideo.com/c/product/43210-REG/Doran_PRLDT_LDT_Adjustable_Luminescent_2_5_.html It is adjustable, but I have not changed it. I have adjusted my personal film speed and development time to what produce acceptable images.. It is all about each person’s need to make final adjustments.

For me there are lessons here in that this thermometer with all it’s stainless steel is less likely to break than the first one I used. As a matter of procedure I always cover this 2.5” luminous head and the Gralab 300 timer before loading film. I am not sure this amount of light will fog film. I don’t want to find out.

John Powers

Bob F. · Sep 24, 2007

Whilst a reasonable general observation, the corollary to this mantra is that: he who has only one thermometer and breaks it is most royally stuffed because he will have to do all his testing again with a new thermometer. He who has compared his thermometer with another thermometer that he has kept safe from corruption, yea unto many generations, is blessed as he shall inherit no such troubles...

It is written.

(just in case)... Bob.

Thanasis · Sep 24, 2007

jp80874 said:
For me there are lessons here in that this thermometer with all its stainless steel is less likely to break than the first one I used. As a matter of procedure I always cover this 2.5 luminous head and the Gralab 300 timer before loading film. I am not sure this amount of light will fog film. I dont want to find out.

If the luminous head is like a radium dial on an analog watch and it comes near the film it will fog. See link:

(there was a url link here which no longer exists)

tac · Sep 24, 2007

thermometers

I have a Kodak Process which I bought new back in the early 80's for $75, as I recall. As it would be difficult and expensive to replace, I use it mainly to calibrate other, daily-use, thermometers. Right now, I am using a "General Brand Digital Stem Thermometer," which reads about 1/10th degree F low; not enough to bother about. It cycles quickly, once per second, is consistent and repeatable. $20 at B&H.
Back when I processed a lot of E-6 and C-41 by hand, I used a Radio Shack indoor/outdoor digital, with the thermistor at the end of a wire- no problems (I made a wire holder/stirring rod for the probe). I think they still sell them for about $10. Accurate, repeatable, slow cycling.

SoulSurround · Sep 24, 2007

tac said:
Right now, I am using a "General Brand Digital Stem Thermometer," which reads about 1/10th degree F low; not enough to bother about. It cycles quickly, once per second, is consistent and repeatable. $20 at B&H.

Today I have developed a test-roll using my digital thermometer... tomorrow I know whether the film-densities differ a lot from my old (alcohol thermometer) process.

Snapshot · Sep 24, 2007

I've purchased a digital thermometer and an analog thermometer, both designed for use with photographic chemistry. I calibrated the analog thermometer to match the digital readout and I use them both. Should one of them fail, I can rely upon the other one to give me consistency (not accuracy) for my processing.

Phillip P. Dimor · Sep 24, 2007

I'd suggest looking into a good used thermocouple on ebay. Mine is handheld and fully waterproof (and submersible). You can also find different probes which are made for use in various substances and situations (ovens, acids, cryogenic fluids). Not to confuse you or make things worse but I had several thermometers at one time and they were all over the map. This one is easy to calibrate, does not drift, survives being thrown, etc.

Tom Hoskinson · Sep 24, 2007

I use a digital darkroom thermometer from RH Designs. I highly recommend it!

See: http://www.rhdesigns.co.uk/darkroom/html/thermometer.html

Arvee · Sep 24, 2007

inexpensive solution that turned out great!

I purchased a Taylor TruTemp waterproof 'pen' type (-40 to +450F, the model is 3519N) from Target for $12.99 and checked it against my Kodak Process III and a Taylor mercury standards lab thermometer (18C to 28C full scale) used for precision temperature water/oil baths. It is right at +/- 0.1F accuracy in a 1L beaker of water stabilized at room temp compared to both these thermometers (which agree exactly) and stable at 0.1F repeatablility. Maybe I just got lucky but I really appreciate the response time. Before I had to wait a minute or so of settling time before I had a moderately accurate reading with the mercury units. Taylor is(was) a good brand but as with all things today, the unit was 'manufactured to Taylor's exact specifications in China.'

Fred

SoulSurround · Sep 25, 2007

THANKS

Hello everybody,

Thanks for all your input. Today I measured the densities of a test-film (developed using my spare digital thermometer) and the results look similar to the results I got with my old alcohol thermometer, so that's great.

I am going to redo the test in a while from now to check consistancy. I guess my lessons learnt are:
1) Make sure you have a reference-thermometer, so that you can always "calibrate" new thermometers against that one.
2) Consistancy (repeatability) in a thermometer is more important than accuracy (measuring the correct temperature)
3) When using alcohol/mercury thermometers, use one that has a scale etched onto the glass.

Thanks again!

fschifano · Sep 29, 2007

I use a Paterson color thermometer as a standard reference. Sells for about $23 here in the US at Adorama. Link here: Dead Link Removed. For regular use, I bought a $10 digital kitchen thermometer. Both agree to withing a few 1/10's of a degree, and the funny thing is that whenever I've had to replace the cheap kitchen thermometer (they give out after a year or two) they get cheaper and the readings are always the same. I've no complaints about using it for C-41 or E-6 either. Spend over $100 on a fragile thermometer for photographic applications? I think not.

montecarlo · Oct 2, 2008

Hello everyone.

I decided not to open a new thread because there are a lot of them referring to darkroom thermometer

I'm preparing to make my first steps into developing myself the BW films so I need some advices in choosing a thermometer.
I saw that there are thos kinds:
- this kind http://www.bhphotovideo.com/c/product/29109-REG/Kodak_EK1122142_Darkroom_Thermometer_F_Scale.html more classical
or this kind
- http://www.bhphotovideo.com/c/produ..._Brand_123617_1_Stainless_Steel_Darkroom.html
As I read the active substance used by the tehmometer is also important (alcohol, mercury etc.).
What would be the differences between the two kind of thermometers shown above. At what aspect I should be more careful ?

Thank you very much.

Nicholas Lindan · Oct 2, 2008

montecarlo;689052 I saw: - this kind [url said:
http://www.bhphotovideo.com/c/product/29109-REG/Kodak_EK1122142_Darkroom_Thermometer_F_Scale.html[/url] and
- http://www.bhphotovideo.com/c/produ..._Brand_123617_1_Stainless_Steel_Darkroom.html
What would be the differences between the two kind of thermometers shown above.

I have had bad luck with several of the stem/dial thermometers: the stem becomes loose and rotates from the dial.

The stirring rod thermometers are accurate enough for B&W, however they read slowly.

For plain-ole-day-to-day use I use a Taylor model 9842 http://www.taylorusa.com/foodsvc/thermo/digital.html. It is calibratable, for those anally retentive enough to feel the urge to do so.

I must be lucky. I have an oodleplex of thermometers of an oodle different types and they all read the same temperature within their resolution limits. Ones that read off I can only ascribe to twisted stems, separated columns or slipped cards. My best thermometer reads to 0.001C and I even use a triple-point cell for calibration - I guess I am anally retentive enough...

fschifano · Oct 3, 2008

tac said:
I have a Kodak Process which I bought new back in the early 80's for $75, as I recall. As it would be difficult and expensive to replace, I use it mainly to calibrate other, daily-use, thermometers. Right now, I am using a "General Brand Digital Stem Thermometer," which reads about 1/10th degree F low; not enough to bother about. It cycles quickly, once per second, is consistent and repeatable. $20 at B&H.
Back when I processed a lot of E-6 and C-41 by hand, I used a Radio Shack indoor/outdoor digital, with the thermistor at the end of a wire- no problems (I made a wire holder/stirring rod for the probe). I think they still sell them for about $10. Accurate, repeatable, slow cycling.

You can get pretty much the same unit at your local WalMart, Target, or other big box store here in the US for about $12 or so in the kitchen gadget aisle. I have a couple of these things and they all read within a few tenths of a degree of each other, and a Paterson color thermometer which I use as a control. That few tenths of a degree F doesn't mean squat in B&W processes.

Phillip P. Dimor · Oct 3, 2008

Earlier on when I was still learning about processing black and white film, I had found a 'new' used Kodak tank and tray thermometer. I thought myself lucky and proceeded to use it without checking it first to make sure it was accurate.

My negatives never came out so good. That's because my thermometer was off by 10 degrees Fahrenheit. Funny how that simple error told me so much about my processing.

I use a thermocouple, mine is a Cooper waterproof hand held one with built in probe. Cooper Atkins and Omega make some nice ones. Some are bench units that will monitor 10 separate probes with a flick of a dial; Neat if you have a jobo and do E6 and C41. That's just me though, it was a one-time investment and I don't worry about it anymore.

I calibrate it by preparing an ice bath. My buddy who is a HVAC student mentioned that an ice bath will be 0C in the center of the vessel (or something close to that effect). I believe that's right but never looked into it even though I probably should. I think salted ice water drops to -10C and plain water to 0C.

Anscojohn · Oct 3, 2008

I have several dial thermometers. I check them regularly against a mercury lab thermometer kept lovingly tucked away in its plastic tube. I bought half dozen of those fellas whilst they were still available and checked them all against each other and all registered the same. I guess I really have more thermometers than I need.
The downside of the lab models is the length: about thirty inches long, so it is not very handy.

Nicholas Lindan · Oct 3, 2008

The best ice bath is slush. If you are using ice cubes then you have to wait for the ice cubes to warm up to 32F - ice can be cooled to any temperature and it is possible to have 32+F water and -10F ice - if the probe/thermometer is in contact with the ice it will read too cold.

Crush the ice to fine crystals, put it into a double-stacked styrofoam cup, add water to cover the ice, cover the resulting slush with Saran wrap to keep the air out and place another sheet of Saran wrap over the cup to exclude air drafts, wait a 1/2 hour and then poke a hole in the Saran wrap and stick the thermometer into the resulting ice/liquid. If your tap water is very hard then use distilled water for both the ice and the water.

Or, you can get one of these http://www.hartscientific.com/products/tpw.htm, or for the simple life one can settle for http://www.omega.com/pptst/TRCIII.html,

Anscojohn · Oct 3, 2008

[cover the resulting slush with Saran wrap to keep the air out and place another sheet of Saran wrap over the cup to exclude air drafts, wait a 1/2 hour and then poke a hole in the Saran wrap and stick the thermometer into the resulting ice/liquid.

********
Would a margerita be better!?

Thermometer

jp80874

Bob F.

Thanasis

tac

SoulSurround

Snapshot

Phillip P. Dimor

Tom Hoskinson

Arvee

SoulSurround

fschifano

montecarlo

Nicholas Lindan

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fschifano

Phillip P. Dimor

Anscojohn

Nicholas Lindan

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Anscojohn

Thermometer

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