Paterson Certified Thermometer reability

[DREW WILEY]

Well, Kodak probably never made it themselves, but subcontracted the manufacture to a specialty supplier having that kind of capability. I like to buy lifetime-quality gear whether for the darkroom or the shop, and long ago discovered that the best gear nearly always turns out to be the cheapest in the long run, as well as the most productive. Now I'll admit that not everyone can drop $250 or $300 on a new glass thermometer. But I've seen surplus unused Kodak Process ones turn up as low as $50.

 

[BrianShaw]

Well, Kodak probably never made it themselves, but subcontracted the manufacture to a specialty supplier having that kind of capability. I like to buy lifetime-quality gear whether for the darkroom or the shop, and long ago discovered that the best gear nearly always turns out to be the cheapest in the long run, as well as the most productive. Now I'll admit that not everyone can drop $250 or $300 on a new glass thermometer. But I've seen surplus unused Kodak Process ones turn up as low as $50.

No doubt that it could have been subcontracted (same with Paterson, I'm sure)... but even then it would have behooved them to specify the certification and tracebility to standards in their sales materials. Otherwise it's just a "trust me".

BTW, as another hobby I do chocolate and sugar work... which requires really exacting temperature control. Even a cheap Chinese thermometer, verified against the NIST-certified Themapen, checks out as reliable and accurate. I think I pay $8 each. They break easily but at that price I'll just keep buying, checking for accuracy, and replacing as needed. I struggle with the buy chap and replace vs buy the best "for life" approaches.

 

[MattKing]

A lot of the Kodak Process Thermometers would have been in the hands of commercial lab operators, who were more likely to have ongoing contact with Kodak support reps.
If a lab was using control strips, but having difficulty remaining in spec, it may very well be the case that the support reps would be able to check the thermometers.

 

[BrianShaw]

A lot of the Kodak Process Thermometers would have been in the hands of commercial lab operators, who were more likely to have ongoing contact with Kodak support reps.
If a lab was using control strips, but having difficulty remaining in spec, it may very well be the case that the support reps would be able to check the thermometers.

Could be and I'd expect that but, oddly, never mentioned in Kodak process control documentation that I've seen. They do write that if processes go wonky that temperature might be one thing out of whack (loosely translated).

 

[DREW WILEY]

There are (or was) mountains of Kodak technical sheets buried away on the web not easy to locate, much of it archived by other parties. Most of the people once in the know in this case at Kodak are no doubt no longer around. But exactly the same kind of thermometer is still being made and available under different branding, with skilled technicians behind it. I have no reason to personally research into it because I'm planning on my own thermometer lasting the rest of my life. But I've also seen plenty of big scientific and lab supply catalog listings, when perusing for other kinds of items I did happen to need at the time. And like I earlier posted, I've actually been in a "just thermometers" warehouse, meaning just serious scientific ones. There will always be a need for them.

 

[Radost]

I found this.
The Lab Depot | Laboratory Mercury-Filled Thermometer, 20-500F (labdepotinc.com)

 

[AgX]

The temperature range is too big for our use, which would mean at same resolution a longer stem. Furthermore the resolution is too course with 2°F

But it is interesting to learn that mercury thermometers are still on sale in the USA. Over here such sale is prohibited both to private and commercial customers (with very few exceptions).

 

[Radost]

So my stem was split at the top. I tried to heat it up to combine and suck it down with ice but it exploded. Getting a thermapen One.

 

[beemermark]

Boil a pan of water, you're thermometer should read 212 deg F. Fill a large bowl with crushed ice and water. Should read 32 deg F. Simple and fast way to check any thermometer. For what it's worth I use a Kodak Mercury thermometer that I've had for probably 30 years. Used to have another one but dropped it.

 

[Arvee]

Boil a pan of water, you're thermometer should read 212 deg F.

*212 deg F at sea level, lower as you go up in elevation so not necessarily an accurate benchmark for certification depending on where you live.

 

[wiltw]

Curious, I just pulled out thermometers between 3 - 35 years old and sunk them all simultaneously into a gallon platic container of randomly warm water from my kitchen tap...

• digital cooking, 74.5
• Westin 3", 74.5
• Jobo Color, 74.8
• Kodak Process III, 74.8

 

[cmacd123]

Curious, I just pulled out thermometers between 3 - 35 years old and sunk them all simultaneously into a gallon platic container of randomly warm water from my kitchen tap...

• digital cooking, 74.5
• Westin 3", 74.5
• Jobo Color, 74.8
• Kodak Process III, 74.8

the 3 inch one likely has a way to adjust it to match. (assuming those are all marked in Ferenhight)

 

[Maris]

I used to be a sales engineer specialising in chemical laboratory equipment with a sub-speciality in thermometry.
There are several ways where a perfectly good liquid in glass thermometers can read wrong:

1. Using the wrong stem immersion depth. 75mm is a common value.
2. Reading a thermometer horizontal when it calibrated for vertical and vice versa.
3. Not allowing for emergent stem error where the thermometer bulb is at a different temperature to the stem.
4.The temperature indicated by a rising thread of liquid, mercury is the worst, is different from the same temperature indicated by a falling thread. Mercury in a capillary moves in little jumps. Precision mercury thermometers are fitted with a vibrator unit to defeat this characteristic.
5.The shape of the liquid meniscus in a thermometer capillary is different for rising and falling. A precision loupe sliding on the thermometer stem can reveal this and indicate if correction is needed.
6.Thermometers exposed to wide temperature swings, particularly high temperatures like 200c or even 300c, exhibit "glass aging" or annealing so regular re-calibration is needed.

Liquid in glass thermometers can be very precise. A Beckman Differential thermometer used for molecular weight determinations can read to 0.01 degrees and can be estimated to 0.001 degrees.
A good platinum resistance thermometer will get you to a millionth of a degree.

 

[Bill Burk]

Every once in a while I drop a little money on a thermometer because I drop thermometers once in a while. I didn’t pay sticker price on this but it’s the “best” I have at the moment. Instructions to fix separated column comes in handy once in a while.

 

[AgX]

I used to be a sales engineer specialising in chemical laboratory equipment with a sub-speciality in thermometry.
There are several ways where a perfectly good liquid in glass thermometers can read wrong:

1. Using the wrong stem immersion depth. 75mm is a common value.
2. Reading a thermometer horizontal when it calibrated for vertical and vice versa.
3. Not allowing for emergent stem error where the thermometer bulb is at a different temperature to the stem.
4.The temperature indicated by a rising thread of liquid, mercury is the worst, is different from the same temperature indicated by a falling thread. Mercury in a capillary moves in little jumps. Precision mercury thermometers are fitted with a vibrator unit to defeat this characteristic.
5.The shape of the liquid meniscus in a thermometer capillary is different for rising and falling. A precision loupe sliding on the thermometer stem can reveal this and indicate if correction is needed.
6.Thermometers exposed to wide temperature swings, particularly high temperatures like 200c or even 300c, exhibit "glass aging" or annealing so regular re-calibration is needed.

Liquid in glass thermometers can be very precise. A Beckman Differential thermometer used for molecular weight determinations can read to 0.01 degrees and can be estimated to 0.001 degrees.
A good platinum resistance thermometer will get you to a millionth of a degree.

Well, you refer here to some errors even not mentioned by a major manufacturer of fluid stem thermometers for calibration use. These errors I regard beyond our range of accuracy.

 

[Maris]

.....But it is interesting to learn that mercury thermometers are still on sale in the USA. Over here such sale is prohibited both to private and commercial customers (with very few exceptions).

A broken mercury thermometer can be dangerous particularly if it is dropped on the floor. Thousand of tiny mercury globules scatter everywhere and if not cleaned up perfectly (particularly from cracks and crevices) then they will give off mercury vapour for years. It used to be a saying in the laboratories where I worked that a single broken mercury would bring a room up to 10 times the maximum industrial exposure limit for a long time.

The cure for a mercury spill is also in many photographic darkrooms; sulfide based sepia toner. A dilute solution of this toner (stinks!) mopped on the floor converts hidden mercury to non-volatile and inert mercury sulfide.

 

[AgX]

Here it is not only about spilling, but to get mercury out of society as much as possible, there is even mercury legislation, covering all aspects of use.

Those who want to keep their mercury thermometers can use them as a calibration reference for other thermometers, for absolute reading, if accurate enough. Or if not accurate enough, just as reference for any deviation over time of a electronic thermometer.

Then for everyday use a non-mercury one.

 

[gone]

I wonder what that "certified" means

Maybe they just stuck it in a punch if ice. If it read 0, then it was "certified". That seems to be a reliably accurate home test.

 

[wiltw]

Maybe they just stuck it in a punch if ice. If it read 0, then it was "certified". That seems to be a reliably accurate home test.

I got curious about certitifcation, and read a number of descriptions. Here is one of them, seems to be representative

"Thermco’s Certified Thermometers are used in temperature verification and calibration procedures. These instruments can be used to calibrate Liquid-In-Glass, RTD, Thermistors, Thermocouples, and Bi-Metal Thermometers. The certified thermometers are carefully inspected to insure they conform to exact specifications and are certified against NlST standards. Each thermometer is furnished with a document proving traceability and a felt-lined leatherette storage case.

Features:

• NIST Traceable
• Standards for Calibration and Verification Procedures
• Calibrated at Specific Temperatures with Correction Factors
• Traceable Calibration Document Included
• Thermometer Packed in Felt Lined Protective Case"

Another certified product

• "Tested and calibrated in H-B’s exclusive triple accredited/registered ISO/IEC 17025:2005, A2LA accredited laboratory against equipment whose calibration is traceable to NIST and DKD/PTB
• Accompanied by a Statement of Accuracy indicating accuracy traceable to NIST and DKD/PTB"

 

[Bill Burk]

Of course a split top puts all helpful advice to rest until the next forum user gets ahold of one of these Paterson’s

 

[radialMelt]

I have two of the Patterson Color Thermometers which are - according to the marketing copy - accurate to .12C. Sounds great, right? I put them both in the same solution at the same time and allow them to acclimate to the solution's temp and I get two readings that are off by .5C. Which one am I supposed to trust?

Are there any current offerings in the way of thermometers that can be trusted fully?

 

[BobUK]

Certified" for the current prices I have seen is a little hard to believe. I would have thought batch sampled might be more believable.
As for digitals, the couple of pricey ones I have had included a warning in the accompanying leaflets saying words to the effect that they are only reliable for about two years then require recalibration.

I wonder how many users here actually use the minimum immersion mark engraved on the back of the glass scale?
A little difficult when only a small volume of liquid is being used.
It does make a difference when taking readings if not immersed to the minimum depth.

 

[JerseyDoug]

One cardinal rule of precision measurement is to never use two different instruments to measure the same thing. Using a third instrument doesn’t guarantee anything either. It just increases the odds of being closer to absolutely correct.

In this case, if one of them is at the high end of the stated accuracy and the other is at the low end they will differ by .48C which rounds to .5C so they could both be within spec. and be perfectly trustworthy.

 

[Milpool]

I have two of the Patterson Color Thermometers which are - according to the marketing copy - accurate to .12C. Sounds great, right? I put them both in the same solution at the same time and allow them to acclimate to the solution's temp and I get two readings that are off by .5C. Which one am I supposed to trust?

Are there any current offerings in the way of thermometers that can be trusted fully?

I’m not sure there is a whole lot you can do unless you spend relatively big money on a calibrated/certified thermometer. I did that years ago because I needed (wanted is probably more accurate ) one for non-photographic purposes, and I use that as a reference for the cheaper thermometers I actually use for photo stuff (several Patersons). They are all +/- a few 10ths of a degree C and that is plenty good for black and white photography. Color processing is more sensitive but I don’t know what level of accuracy is needed.

 

[radialMelt]

One cardinal rule of precision measurement is to never use two different instruments to measure the same thing. Using a third instrument doesn’t guarantee anything either. It just increases the odds of being closer to absolutely correct.

In this case, if one of them is at the high end of the stated accuracy and the other is at the low end they will differ by .48C which rounds to .5C so they could both be within spec. and be perfectly trustworthy.

Correct me if I'm wrong but if they are supposed to be accurate to +/- .12C, then the max difference between the two thermometers should be .24C, no?