Mercury thermometer recommendation?

ic-racer · May 31, 2023

Unicolor Precision Thermometer (like pictured).

Advantage, without the metal cage, it is easer to clean after measuring temp of the chems in Jobo bottles. The yellow background for the mercury column makes it easy to read, even though the column is very skinny compared to the Kodak Type 3.

Mine reads in "C" has a calibration mark scribed near the printed 20C mark.

This is my most used thermometer. I use it to check the Jobo developer bottle with almost every run.

ic-racer · May 31, 2023

"Perfect" brand lab thermometer (like pictured):
Mine has a white background and reads in "C". The scale is longer than the Unicolor, so the divisions are closer. It is a little harder to read than the other two. My least used thermometer.

ic-racer · May 31, 2023

Kodak Color Thermometer (like pictured):

This one features blue alcohol on white background. It is easy to read and responds very fast. Mine reads in "C" and the limited scale makes the numbers spread out so it is easy to read.

Curiously, its container has more warnings than any mercury thermometer I own. Due to its 29 CRF Part 1910 danger for possessing certain diazo dyes and its inherent flammability.

ic-racer · May 31, 2023

Powers Fotopanel (like pictured):

My thermostatic mixer has a built-in thermometer. The dial reads in "F" so readings need to be converted in my darkroom. The dial is very easy to read and I have it conveniently mounted at eye-level. Per the manufacturer's specifications the thermometer is described as follows:

Horizontal 2-1⁄6" (52mm) long bulb with temperature range of 30° to 103° F (-1° to 39°C), the thermometer features an external calibration screw of zero reset, with a response speed of Gr. 1 per AMS PH 4.7-1958

Radost · May 31, 2023

ic-racer said:
Kodak Color Thermometer (like pictured):

This one features blue alcohol on white background. It is easy to read and responds very fast. Mine reads in "C" and the limited scale makes the numbers spread out so it is easy to read.

Curiously, its container has more warnings than any mercury thermometer I own. Due to its 29 CRF Part 1910 danger for possessing certain diazo dyes and its inherent flammability.

View attachment 340277

Pretty sure this one Is mercury

ic-racer · May 31, 2023

Radost said:
Pretty sure this one Is mercury

Flammable blue mercury

Chan Tran · May 31, 2023

My two thermometers are pretty close.

Agulliver · Jun 1, 2023

DREW WILEY said:
What's all the fuss about mercury in thermometers anyway? Do you go around dropping lenses and enlarger carrier glass too, or brown glass bottles full of chemicals? I can appreciate the point in beginner darkroom classes perhaps; but they aren't likely to need an expensive precise thermometer anyway. Metal dial-type ones are readily available.

In some quarters there is a move away from actually assessing risks properly and doing activities which are safe, but which could be made just that little bit safer. Probably fear of litigation.

In a home or even shared dark room, a mercury thermometer represents a tiny risk. Breaking a bunch of them and leaving the spilled mercury in a nice, deep carpet where the vapours can get into the room would be a problem. So you have a no carpet in your dark room - which you shouldn't anyway due to using liquid chemicals....and its wise to have a mercury spill kit around - either some sulphur powder to mop it up or a little sponge type device that safely screws into a tight container that can be disposed of when it's full. Costs all of five quid.

That said, unless you're in the habit of abusing your thermometers, there's no real practical advantage to dark room users of mercury over the non-toxic spirit thermometers. The latter come in several colours which might be easier to view.

I have no worries about using our old oral thermometer at home which is a mercury thermometer. Even if I did somehow chew down on it, I'd be far more concerned about the glass than the mercury.

But.....ooooooh bogeyman....mercury is poison! So are parsnips if you guzzle enough. Especially "in the state of California".

Chan Tran · Jun 1, 2023

ic-racer said:
I have a number of thermometers in my darkroom for comparison:

Kodak Process Thermometer type 3 (like pictured) features a metal support and protective casing for the bulb. Main advantage, other than durability, is the wide and very easy to read mercury column. Disadvantage is that mine reads in "F" so readings in my darkroom need to be converted.
I use this as my 'standard' by which other thermometers are compared. This is a beautiful item from the heyday of Kodak's involvement in film.

I'd recommend this one as they are still available on the internet and, as previously discussed, they can last many many years.

View attachment 340266

You said it reads in F? I can see in the picture there is the C scale on the left side? You can see clearly the C scale on the picture of mine.

ic-racer · Jun 1, 2023

Chan Tran said:
You said it reads in F? I can see in the picture there is the C scale on the left side? You can see clearly the C scale on the picture of mine.

“…like pictured” except mine reads in “F.”

Here is a picture of my actual thermometer. This is super easy to read, even under safelight. Even though it does not have the "C" scale, it has large indicators right at 20C and 24C!

DREW WILEY · Jun 1, 2023

Thermostatic mixers involving valves are not highly accurate at all. If you want that, you need a true scientific grade recirculating thermoregulator.

pentaxuser · Jun 1, 2023

DREW WILEY said:
Get the real deal and be done with it : a Kodak Process Thermometer. These were individually certified, just like all true scientific lab thermometers. Even if you use cheaper thermometers or even an electronic one, you should have one of these on hand as a reference. But it's the only option I now use.

Drew, how much do these Kodak ones cost compared to those that are quite cheap but are guaranteed to within 0.2 degrees C?. I have one that has such a guarantee and my Jobo ones read the same. The guaranteed one cost me less than $12 but it isn't a Kodak one. It was made by Fallowfield of Middlesex, London

How inaccurate does a thermometer have to be be to affect the quality of a negative or print for (a) colour neg (b) colour RA4 print (c) b&w neg and (d) b&w print

I had always thought that the guarantee given above of 0.2 degrees C was good enough. However how far beyond this kind of accuracy does the thermometer have to stray before the negative's or print's quality be affected to the extent of being detectable with the human eye

At some point in terms of getting a "bang for buck"( my thanks to Charles Erwin Wilson here ) serious diminishing returns set in making extra expenditure just not worthwhile as there is no perceivable benefit to be achieved, or so I would have thought

My first teacher at a darkroom course which was for b&w used to say an accuracy of half a degree centrigrade was good enough to use the development times given to us which were the official times for 20 C

Thanks

pentaxuser

DREW WILEY · Jun 1, 2023

Kodak Type 3 Process Thermometers were around $250 new, which is right about what someone would pay for a certified scientific thermometer similarly clad today. But they turn up form time to time for considerably less today, either used, or never sold to begin with. Certifying involves an actual test of that very item, not just a "guarantee", which might not mean anything more than BS marketing. And being metal clad, these are quite durable.

RA4 is fairly tolerant. I try to keep within a couple degree plus or minus of 30 deg C. More than 3 deg plus or minus, and you risk a little color shift. But there are other processes like making matched color separations negative where it is helpful to be way more precise.

What is most important, however, is consistency. Any given thermometer has to read the same each time. And just like with light meters, it's helpful to have a standardized reference on hand to check things. But I don't use secondary thermometers at all, just the trustworthy Kodak Process one itself. Even my electronic thermometers just sit in a drawer unused.

pentaxuser · Jun 1, 2023

Thanks Drew It certainly sounds as if the tolerance of RA4 is large enough for a guaranteed within 0.2 degrees C thermometer However what about C41 and b&w negs that I asked about, what are the real dangers, if any, that such as the guaranteed within 0.2 degrees C thermometers might not meet their own guarantee and if so by how much can they fail to meet the guarantee and still produce acceptable negs?

I can't speak for U.S. law but a printed guarantee in terms of fractions of absolute degrees from a company in the U.K. has to be more than marketing B.S. unless its wants to fall foul of the U.K. sale of goods law

pentaxuser

Chan Tran · Jun 1, 2023

pentaxuser said:
Thanks Drew It certainly sounds as if the tolerance of RA4 is large enough for a guaranteed within 0.2 degrees C thermometer However what about C41 and b&w negs that I asked about, what are the real dangers, if any, that such as the guaranteed within 0.2 degrees C thermometers might not meet their own guarantee and if so by how much can they fail to meet the guarantee and still produce acceptable negs?

I can't speak for U.S. law but a printed guarantee in terms of fractions of absolute degrees from a company in the U.K. has to be more than marketing B.S. unless its wants to fall foul of the U.K. sale of goods law

pentaxuser

Most thermometers although not very accurate (C41 process called for 0.5 degrees F so it's about .2 or .25 degree C) and not sufficient accurate for something like C41 but they are much better in term of repeatability so all you need to know is the amount of offset your thermometer needs. But I can keep the chemical at the right temp when I pour it in the tank but it's cooling off while developing. This is a bigger problem.

MattKing · Jun 1, 2023

Historically, a large proportion of the labs using Kodak Process thermometers were also using and evaluating control strips, which in turn gave feedback on issues like temperature control.

DREW WILEY · Jun 1, 2023

Guarantees mean next to nothing. It's almost impossible to enforce them. One of the most reliable manufacturer's I ever dealt with simply printed on their labels : Our reputation is our warranty.
That company has been around a 140 years now.

pentaxuser · Jun 2, 2023

DREW WILEY said:
Guarantees mean next to nothing. It's almost impossible to enforce them. One of the most reliable manufacturer's I ever dealt with simply printed on their labels : Our reputation is our warranty.
That company has been around a 140 years now.

Well we may need Matt King here to decide if "Our reputation is our warranty" is a guarantee that is enforceable in law, Drew but I'll venture to say that it is likely to be less enforceable that stating "guaranteed within 0.2 degrees Centrigrade on the label with the company's name and address

Can I take it that example you gave of a guarantee was not the one on your Kodak thermometers?

pentaxuser

Chan Tran · Jun 2, 2023

My Kodak Process Thermometer Type 3 doesn't have a warranty. It does said the Celsius scale is accurate to +/- 0.125 degree at 15,20,25,30 and 40C. and to+/- 0.25 degreee over the rest of the scale.

DREW WILEY · Jun 2, 2023

No, Pentaxuser, not the Kodak thermometer. it was a routine label and tech sheet statement by a privately held industrial corp considerably bigger than Kodak. After six generations of family ownership, it was finally sold to Warren Buffet, and nothing has otherwise changed. But even when specific warranties are in print, once a product line is discontinued or the company is bought out, unless there is a contract assuming retroactive responsibilities, they're automatically void. And such changes of ownership occur very frequently among publicly-traded companies. But I don't think glass thermometers are the kind of thing that would tempt a corporate takeover very often. The vultures generally prefer bigger and more rotten carcasses.

Mercury thermometer recommendation?

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