Thermometer advice needed

I have a beautiful classic glass and stainless Kodak Process Thermometer but although it is great for use as a standard to calibrate to, for obvious reasons I'd rather not use it for daily darkroom duties. I have a Premier dial thermometer that can be calibrated but everything else about it is awful, its scale goes from 15c to 70c so the degree increments are infinitesimal and 20c is way down at the lower extreme of the scale, parallax is a problem and the needle vibrates unreadably with the slightest touch.
A new thermometer is the single improvement that would make my darkroom life immeasurably easier. I'd like to find something that is accurate, can be calibrated, easy to use and read, designed for the Black and White processing range and rugged enough for everyday use. Either Dial or digital.

Any suggestions?

I use an old small dial thermometer. Had it for years. It goes from -20C to 100C. Can't remember where I got it from but it has the Cooper name on its face. It is small, about 6" long and the face dial is about size of a quarter. This has worked well for me for BW and colour over the years. If I were to purchase a new one today, I'd think seriously about a digital one. Don't really need it accurate to .10 but like the idea of a reading at glance without having to think about the little tick marks on a dial. Old eyes?

I just got a thermometer that might suit your needs. A Weston 3" dial, metal parallax reflector between C and F scales, 25 to 125F and -4 to +52C, half degree marks between 65-80F and 20-25C, calibrateable. Forgot the price, but I think B&H has them. Responsive, easy to read, nice scale spread.

Lee

Taylor makes a digital instant read thermometer, p/n 9865, that can be re-calibrated. If you're process is set up to match the Kodak readings, you can adjust the Taylor to match. It's part of their commercial line, I saw it at the local restaurant supply store. I think it was around $35.

Thermometer

Flotsam-buy the weston type thermometer. I have couple of them. Nothing to break;they are accurate and fairly cheap. I think Calumet has them also.
Peter

Remember ANY thermometer that can be calibrated is, by definition, inherently wrong. Stick with and get used to using the Kodak. You'll never have to calibrate it and if you are calibrating your processes to it now, keep using it. There's nothing wrong in caring for your thermometer as you would your film or anything else you depend on.

You know, one of the best thermometers I've ever used is a small digital therm. meant for food use. I have x-checked this thing with a few other therms, and it appears to be right on. it has two problems, however. 1) You can't get the head wet, since that would destroy it, and 2) it has no clip, so you have to hold it. It works very well for checking solution temperatures, but I wouldn't want to use it to try and bring a solution to a temperature. That would be painful.

Paterson calibrated spirit thermometers are (allegedly) accurate to 0.3C and come in Colo(u)r and B&W versions. Under a tenner in the UK - presumably available in the US for an equivalent quantity of beer tokens....


Bob.

I had half a dozen dial thermometers but many of them gradually went off. I'm not an expert in this area, but those dial thermometers suffered from temperature outside the measurable range and/or mechanical shocks. I no longer use a dial thermometer for anything critical.

For one thing, if your spirit/mercury/whatever thermometer is in a standard size, get a good armor. You'll feel much easier to do calibration more frequently.

Digital thermometers... you can find an entry level lab thermometer with accuracy (not readability) less than 1C for $40-60 range. But if you are concerned about 20C or 25C only,
you could get a cheaper one and note the offset against your standard thermometer. Many digital thermometers have long probe length and deep immersion requirement for accurate reading. I'd pay a bit extra for short immersible probes, which is very useful when measuring small quantities of developers or whatever.

After all, depending on your frequency of thermometer use, getting a couple of cheap and good spirit thermometer with armor may do. A 6" one for 0-50C can be had for a couple of bucks a piece from surplus lab supply houses. (If the armor is really good, and if you are careful, they can be good enough as a stirring paddle... though I wouldn't use it to dissolve solidified powder.)

Now for spirit thermometers... for regular film processing in daylight tank, this doesn't matter much, but if you have to measure temperature under safelight, get a BLUE spirit one. Red doesn't have enough contrast. And this is one place where a good digital thermometer with a big display can be a lot easier to use.

There is another kind of thermometer... infrared radiation (noncontact) thermometer. They are good for contamination-sensitive stuff like emulsion, but they are generally not accurate enough for developers. They are probably more useful in kitchen.

Bruce, This an old style glass and mercury Kodak Process Thermometer that is only marked in fahrenheit (the later C/F ones were sloppily engraved IMHO). A real treasure and not to be trusted to a clumsy butterfingers like myself in daily use. I'd like to use it to calibrate sturdier thermometers that can actually be replaced if they are broken.

I used a Weston Mirroband for years and loved the way that they deal with parallax. That one wasn't calibratable and I've never been clear on whether they make one that is.

Dave, Digital would certainly be easy on the old eyes. I'll check that out.

Thanks all

Neal,
I know exactly what you are saying about the Kodak. I have and use an old Jobo Process mercury thermometer. It floats in bubbling water and is calibrated in celsius and if it breaks I will get another one. Bob F and Ryuji make good reasoning I think. But you are going to be using it daily (I hope) so it is to your needs that must be met.

http://www.control3.com/4373p.htm

That's the one I want. BUT I can't find anybody locally that sells it for a reasonable price. Found a few US suppliers but they all wanted both arms and a leg for shipping. Wow is me.

Look at this page - http://www.jobo-usa.com/products/miscprod.htm#Thermometers and look for the Jobo Color Thermometer. It uses blue spirit, not mercury, there is less issue if you break it. It goes from 15 to 30C in 0.2C increments. Immersion level is about 1 inch.

This will be much more accurate and precise than any dial or inexpensive digital thermometer. Don't forget, even if you have a digital thermometer, if it only reads to 1 degree increments, the uncertainty in your measurements will be +/- 1 degree. The Jobo I've listed above will be much more precise.

I have a $15.00 digital cooking thermometer (eBay) that I have been using over the past year. Its range is -40 degrees F to 450 degrees F and reads in 0.1 degree increments. It has a long stainless steel probe which I find useful.

I periodically check it against our calibrated lab standards and have found that it is in good agreement (plus or minus 0.1 degree in my range of interest).

Thermometer?! I just put my finger in.
No really, I have 3! 2 westons and 1 Spiratone. Each has a nut for calibration. In 20 years, they seemed to have been moved slightly so each one give me a different temp.

I kid you not, I stick 2 or 3 in solution, average it out, and I go from there. Works for me. They are all 1 degree off each other so I figure, one must be okay.

I'd go for a thermocouple personally.. Search on E*ay for 'thermocouple' and look for an older Omega thermocouple or something similar. There are industrial submersible thermocouple probes, etc. Many of the Omega thermocouples have multiple probe inputs so you could keep track of many different temperatures.

I have a Cooper/Atkins FW2000 and it is 100% waterproof. I've seen pictures of this unit being submerged in a bucket of ice and giving a reading. The display is digital, the readout is quick and more accurate than you'd probably need. You can also calibrate it yourself if you wish.

It might be a bit overkill but i've gone through too many thermometers. My kodak tank and tray thermometer is off by 10C !!!

Phillip P. Dimor said:

It might be a bit overkill but i've gone through too many thermometers. My kodak tank and tray thermometer is off by 10C !!!

Click to expand...

My old thermometer used to be off by 5C but it was always off by exactly 5C. Perfectly repeatable in the range I needed to check.

I have a non-adjustable Tele-Tru dial thermometer I must have bought sometime in 1973 or 1974. I don't know how truly accurate it is but it is consistent. Results have been good, so I use its temperature readings as baseline. I doubt its being made anymore. I also have a Weston dial thermometer that I calibrated to the Tele-Tru and now use it the most. It's nothing special but it's been holding the calibration accurately.

Just thought I'd tack my final decision to the bottom of this thread.

I think that my darkroom conditions favor using a dial thermometer over a digital. The Weston addresses all of my original complaints, the mirror helps the parallax and the B&W temps are in the middle of the scale.
It appears that both the large and small dial have the all-important cailibration nut so I think that I'll go for the small dial to minimise needle vibration. I figure that a small needle will vibrate less and damp down quicker.

With the news about B&H, I think I'll put in an order with Adorama. I'd use Calumet but I need to order a bunch of paper too and their prices awfully high on that.

Thanks to everyone for the help.

I picked up a Pyrex brand digital thermometer at Sears for about $15 a few months back. It has a probe with a cable that's about 1 meter long and is very accurate. It runs on a single AAA battery.

One needs in talking about thermometers understand the difference between
- accuracy
- repeatability
- readability

Most digital thermometers offer very high refinement in readability and modern ones a relatively good repeatability for readings of 0.2C or finer. They are, however, typically inacurate and most use simple chipsets and assume a circuit and probe linearity that they don't really have. One can, in praxis, calibrate them to acurately read out at one or two temperatures. That's where a good reliable, repeatable and traceable reference comes into the picture.

The Kodak process thermometer type-III is NIST traceable and has quite a few calibration points in both C and F. They cover a larger range, are made of heavy glass and protected by a nirosta sheath so they are very hard to read but very acurate at the known points. They offer moderate repeatability due to their poor readability. Their advantage is the large range, robustness and economical price---- just a few calibration points against a NIST traceable reference will cost much more.

I also have several Jobo photographic thermometers they call "color". They have good readability and repeatability but very poor acuracy. My mercury Jobo is a bit better than the spirit one but the spirit version is much easier to read. They are OK for uncritical B&W processes but not all B&W processes are uncritical. Once I started doing some process control I had to realize that these thermometers were often insufficient.

I also have a set of high precision laboratory thermometers for use in the 20C range and readable to resp. 0.1 and 0.2C. They too are, of course, mercury and very very thin--- and are stored in special cases. Since these thermometers are very acurate and I'm really mainly interested in only a few points I use them to calibrate my other thermometers both spirit and digitial--- including the digital temp built into my Nova 2000 controller--- in that range and use one of my Kodak type-IIIs to get some other points, especially the "magic" 100F. Calibrated against these standards the "inexpensive" digitals are quite adaquate and appropriate to the task and suited to even the most stringent of process control regimes.

From Google enter, vee gee 81125 . Or go www.novatech-usa.com.
I may buy a couple of 1 or 1.75 inch Vee Gees; 25 to 125 F.
Quick, dial/stem thermometers; $4 and $7.
I droped the one I had. Dan