Thermometer

[SoulSurround]

Today my glass (alcohol) thermometer dropped. As I quite precise about temperature when it comes to mixing my film-developer (I use a densitometer to check zones from time to time)... I am quite crushed by the event.

But today I also found out that the scale of this alcohol thermometer can slide up and down the column quite easily (by tapping the thermometer on either end) changing the read-out! So I don't want to get back to using this kind of thermometer.

I also have a digital thermometer with a metal probe(Dead Link Removed), but I didn't use this one because I am not sure about the consistancy (after all that's what's most important) and it reacts kind of slow to minimal temperature variations.

My question: what thermometer do you use? Is digital better than analogue... or the other way around (like photography ).

Thanks in advance!

 

[David H. Bebbington]

Today my glass (alcohol) thermometer dropped. As I quite precise about temperature when it comes to mixing my film-developer (I use a densitometer to check zones from time to time)... I am quite crushed by the event.

But today I also found out that the scale of this alcohol thermometer can slide up and down the column quite easily (by tapping the thermometer on either end) changing the read-out! So I don't want to get back to using this kind of thermometer.

I also have a digital thermometer with a metal probe(Dead Link Removed), but I didn't use this one because I am not sure about the consistancy (after all that's what's most important) and it reacts kind of slow to minimal temperature variations.

My question: what thermometer do you use? Is digital better than analogue... or the other way around (like photography ).

Thanks in advance!

Digital is easy to read - just because it reads to 0.1°C, that of course doesn't mean it's accurate to 0.1°C! I have always used a mercury thermometer - accuracy is not as important as consistency, after you have developed a few films even with an inaccurate thermometer, you will have learned to compensate for this and get the results you want.

Regards,

David

 

[SoulSurround]

Digital is easy to read

I find analogue easy to read too, plus you get a better indication when the temperature of a fluid changes rapidly when - for example - rinsing film.

I have always used a mercury thermometer - accuracy is not as important as consistency, after you have developed a few films even with an inaccurate thermometer, you will have learned to compensate for this and get the results you want.

I know, but are mercury thermometers still available... and don't they have the "sliding scale" problem?

 

[Neal]

Dear SoulSurround,

In the U.S.A., mercury thermometers are generally unavailable. If you like analog thermometers, check out http://www.omega.com/pptst/GT-RL_THERMOMETERS.html. I don't know how they handle international sales.

They also sell some very nice thermocouple readouts and probes. In general, the smaller the probe, the faster it will read.

This seems to be an economical reader: http://www.omega.com/pptst/GT-RL_THERMOMETERS.html

Here are probes I've used in the past (but not for photography) http://www.omega.com/pptst/KTSS_JTSS_chb.html

If nothing else, the site is fun to poke around in.

Neal Wydra

 

[Bruce Osgood]

My alcohol thermometer from Kodak has a scale that appears to be etched in the glass. I've had the occasional separation in the column that heating it until all the separation rises to the top most area and then letting it settle back to room temperature has solved.

I'm a firm believer that any thermometer that is adjustable is inherently wrong, digital or otherwise.

I would stick with the alcohol thermometer. As you note, it is not difficult at all to read.

 

[Bob F.]

I bought four Kaiser precision thermometers at the same time from Silverprint having broken one in the past. They all read identically to within 0.2C so if one breaks, no sweat.

Even if they were a significant amount out against each other, it would be a simple matter to mark each with the offset from my usual working thermometer at my most usual working temperatures of 22C and 38C.

I suspect you will pay a considerable premium for a digital thermometer that can repeatedly measure to an accuracy of 0.1C.

Good luck, Bob.

 

[Jim Jones]

I used dial thermometers in the past with frequent checks against a mercury or alcohol thermometer. Sometimes they needed adjusting. A loose scale on an alcohol thermometer can be expoxied in the right position. If the column in an alcohol thermometer is not seperated, or the scale not loose, I would rely on it more than a dial or digital thermometer.

 

[fotch]

I purchase a couple of Kodak Process Thermometers (used) that are mercury glass encased in stainless steel type enclosure. I have read that they are the most accurate and have the higher temperature range for color processing and chemical mixing. The ones I have all give the same reading.

FWIW

 

[SoulSurround]

If the column in an alcohol thermometer is not seperated, or the scale not loose, I would rely on it more than a dial or digital thermometer.

I have the same feeling... but the mercury Kodak Process Thermometer that fotch is talking about appeals to me even more... especially if they are encased in stainless steel. But I guess they don't make them anymore. What would be a "fair" price second hand?

 

[Photo Engineer]

A man who has one thermometer knows the temperature, but if he owns more than one, he does not know the temperature.

I have about 7 or more thermometers, two of them the original Kodak mercury thermometers in metal and almost 1 foot long. The two Kodak thermometers read virtually identical values in a solution, to within less than 1/2 degree, but the others vary from 1 - 5 degrees. (this is all F but they have C scales as well).

These are a mix of dial, digital, mercury and alcohol. All vary.

The thing that is important here is that if you use one thermometer for one job, and it is off a bit, you will still get good results as long as you are consistant in everything you do every time you do it.

PE

 

[haris]

Go to pharmacy shop and buy (order) calibrated and certified thermometer for chemistry/pharmaceutical laboratories. That is, if you want precision and consistency. Of course, at price that mach precision and consistency of thermometer

I have one Kaiser precision thermometer, 2 bought from fotoimpex (don't know manufacturer), one Hama angled for paper trays and one old USSR. Last one is interesting, it come in blue plastic covering and cap of that covering is wide enough to serve as cap for bottle when thermometer is into chemical bottle, so thermometer stay selfsuported in bottle and at same time bottle is closed

They all work for me

 

[fotch]

I have the same feeling... but the mercury Kodak Process Thermometer that fotch is talking about appeals to me even more... especially if they are encased in stainless steel. But I guess they don't make them anymore. What would be a "fair" price second hand?

Two came off of the auction site, First one about $21, second one about $18, and the third from an ad at photo.net, cost about $23. The PNet on is brand new, and one of the bays is like new. The one that has seen more use is still in very good condition. All agree within 1/4 degree.

I have seen them go for above $60 on the bay so take your time and you will find one at a more reasonable price.

I mainly purchase the last one because it was new and had a lower price although the seller way over did the shipping and it more in shipping than it should. He did not pocket the money, just spent more to ship.

FWIW

 

[pentaxuser]

I was given two JOBO thermometers with my secondhand JOBO processor. Both read exactly the same when in the processor. I broke one and obtained a replacement secondhand JOBO thermometer from one of the sponsors here,Nova.

It also read exactly the same as the original JOBO. This leads me to believe that JOBO thermometers are consistent and probably very accurate. I think mine was £5 so not expensive and it is not digital and records any changes in temperature quickly. The scale is built in so the tube cannot slide and give inaccurate readings. It is of course glass and vulnerable to any impact such as dropping it but I'd recommend one.

pentaxuser

 

[Fotohuis]

The accuracy of the mentioned digital thermometer is 0,3 within the used photographical temperatures 10-40 degrees C.
It's about the same of a nice mercury thermometer. Indeed a lot of digital thermometers are not linear in this area from 10-40 degrees C but this one is a selected industrial type.

But on request we can give an iso/DIN certificate of the thermometer, it's just a matter of enough effort and money involved

 

[George Hart]

Today my glass (alcohol) thermometer dropped.

That's a pretty clever thing for a thermometer to do, unless you are referring to the column of liquid inside it!

 

[cao]

I have a number of digital thermometers, but have reserved one Hanna Checktemp-1 (advertised accuracy +/- 0.3C) as a reference. For any other, I compare the readings over 20-40C, and I note the deviation. For instance, the Checktemp I use under-reads my reference by about 0.3C. So I get my pre-soak and developer to 21.7C for a 22C run. I have a very fast stick thermometer at the college darkroom I oversee, and that under-reads by 0.5C over the range of interest. All these readings appear repeatable, and I spare myself a visit by a hazmat crew should I drop one of these. Some time, I'll take my reference over to the school's material sciences lab for a calibration, but as Ron suggests, repeatability is the main thing, and it seems to be there.

Curiously, I started souping with a spirit thermometer designed for chocolate tempering under the impression that it was good since chocolate work is fairly precise. The thermometer under-read by about 0.8C. Until I bought my reference, I hated the contrast I was getting from TMX with the suggested time/temperature. Whites were completely blocked up, and I thought Kodak was out to lunch on their recommendation. Now I find the film quite good developed as recommended. The thing is that if you want to communicate results to others, accuracy is important as repeatability.

 

[SoulSurround]

The thing that is important here is that if you use one thermometer for one job, and it is off a bit, you will still get good results as long as you are consistant in everything you do every time you do it.

OK, I guess my question is related to this. As I am also tempted to use my digital thermometer (because it is less likely to fall and break)... my question is also; are digital thermometers consistant? I don't really care about accuracy... but as digital thermometers look more like a "black box" to me I am doubting their consistancy.

 

[GeorgesGiralt]

Hello !
If you do color work (E6 for example) go and buy a medical thermometer. It will have a narrow range but very good checked accuracy as it has to be quite precise at about the 36~39 ° C range. Which is perfect for E6 processing. Last but not least, they are damn cheap....

 

[haris]

OK, I guess my question is related to this. As I am also tempted to use my digital thermometer (because it is less likely to fall and break)... my question is also; are digital thermometers consistant? I don't really care about accuracy... but as digital thermometers look more like a "black box" to me I am doubting their consistancy.

I would say they are acurate as any other digital product. For example: Tou have old mechanical watch. Now, on the other hand you have cheap quartz watches, which are in most cases more precise and more consistent then mechanical watches. Then you have good quality and more expencive quartz wathes, with even more precision and consistency, and all way up to atomic time measuring machines with "perfect" precision and consistency.

Now, would you lose trust in yours let say your mechanical Rolex, and replace it with cheap quartz wach?

Simillar with digital thermometers. I again will say: Buy calibrated and certified laboratory thermometer, and no matter if they are spirit, mercury or digital, you will have precised and acurate thermometer.

 

[Steve Goldstein]

Yet another resource is Brooklyn Thermometer Company (http://www.brooklynthermometer.com). I think they still sell mercury units, as well as alcohol, in a variety of styles, temperature ranges, and accuracies including ASTM-certified.

 

[SoulSurround]

http://www.brooklynthermometer.com

Thanks for the link Steve... by the way, it's for black and white work. So mainly looking for a scale that is optimized for 20 degrees celcius. Let's see whether it's a problem if they have to ship mercury to Europe...

 

[Photo Engineer]

OK, I guess my question is related to this. As I am also tempted to use my digital thermometer (because it is less likely to fall and break)... my question is also; are digital thermometers consistant? I don't really care about accuracy... but as digital thermometers look more like a "black box" to me I am doubting their consistancy.

I use a Corning hotplate with digital readout to make my emulsions. They are not only accurate but they are consistant. I check them with my dial thermometers and my stem thermometers, and although they may not agree in value, they do repeat what they all read over and over.

So, yes, my digital thermometers are consistant. Battery driven digitals just stop working rather than give the wrong reading.

PE

 

[blanco_y_negro]

I have only used alcohol or mercury thermometers, and have never experienced any problems. As long as the scale is etched on the glass tube, I don't think one should worry about it. That said, I would give higher priority to consistency than accuracy.

 

[CBG]

A man who has one thermometer knows the temperature, but if he owns more than one, he does not know the temperature.

I have about 7 or more thermometers, two of them the original Kodak mercury thermometers in metal and almost 1 foot long. The two Kodak thermometers read virtually identical values in a solution, to within less than 1/2 degree, but the others vary from 1 - 5 degrees. (this is all F but they have C scales as well).

These are a mix of dial, digital, mercury and alcohol. All vary.

The thing that is important here is that if you use one thermometer for one job, and it is off a bit, you will still get good results as long as you are consistant in everything you do every time you do it.

PE

I am more concerned with repeatability than conformance to a standard temperature. With various thermometers why not establish one unit as one's own lab standard, and establish a correction for all the others to the temps one needs.

Say at 68 degrees by the standard unit
- for thermometer A add one and a half degree to make it match
- and subtract a half from thermometer B...

And so on.

Not too hard to dump them all in a water bath and just note needed corrections.

So, I like having several to see if one has suddenly gone looney. I use two meters to check each other and others for back up to decide in case there's an argument.

Best,

C

 

[SoulSurround]

With various thermometers why not establish one unit as one's own lab standard, and establish a correction for all the others to the temps one needs.

Well, I did do that with my (dropped) alcohol thermometer and my digital one. But back then I already got the feeling that they didn't always match "spot on". And also at different temperatures (15 degrees, 20 degrees and 35 degrees) the differences were not the same. But I will shoot a test-roll soon and find out if the value for 20 degrees celcius is "right" on my digital one.