a good darkroom thermometer?

R

Ronald_H

Don't call me Ron
Local time
11:29 AM
Joined
Feb 24, 2008
Messages
1,727
Some of my recently developed rolls show inconsistent results. As it is rather warm in my house and the tap water is rather cold, my best guess is that my times are incorrect due to incorrect temperature readings.

So, what is can you guys recommend as a decent darkroom thermometer?
 
I'vee been using spirit-filled thermometers made for school chemistry lab use.
Accurate enough for BW. Graduated to 1 degree C increments, half degrees clearly visible. And very inexpensive, often sold in school supply shops.
 
I'm using this one, it costs about 10€ and can be found in the Netherlands too I'm sure:

http://is.gd/1QC1g

If you want to allow more room in development temperatures you might want to try Diafine.
 
I keep a several one gallon plastic jugs filled and in the darkroom for use in photo developing. I have found that that allows me to do all chemistry at the same temperature. Small adjustments may be necessary seasonally, but that's not so difficult to adapt to. When my first jug is used up, I refill it and move it to the end of the line and use jug #2, etc.
 
The ideal is two thermometers, a master and a slave. I use a mercury-in-glass Brannan lab thermometer as a master. The slave (typically a cheaper thermometer, of any kind with an adequate scale) is checked periodically against the master: this is especially important for digital and dial thermometers. If you break the slave, you can calibrate a new slave to the master.

By 'calibrate' here, I mean that you mix some water to (say) 20C (as determined by the master) and then check the slave reading; 19.5C, perhaps, or 20.4C. Thereafter you use 19.5 or 20.4 as your standard temperature. Another slave might read 20.8, so with that one, you always use 20.8.

The great advantage of this system is that it is highly consistent, even if the master is not totally accurate -- and you can always add or subtract a degree (or more) if you want to work at higher or lower temperatures instead of varying time.

Cheers,

Roger
 
Does not matter if it is accurate, it needs to be be repeatable and then you compensate.

I use two Kodak process ones only to check the dial ones I actually use . All measuring devices are this way in industry with a calibration tracing back National Bureau of Standards.
 
Weston dial thermometers are usually pretty accurate. All the dial thermometers that I've seen have a hex nut around the shaft under the dial. Hold that with pliers and you can turn the dial to match the reading on your process thermometer, or other thermometer known to be accurate.

http://thepriceofsilver.blogspot.com
 
Just for B&W film developing I've been using a cheap thermometer from the kind supposed to be used in aquariums. So far, it works... Water temperatures around here are usually near 20º C (down to 15ºC in Winter, up to 26ºC in Summer)
Joao
 
I liked my kodak thermometer, the long glass kind that costs about $30. It broke and man did it stink! It smelled like crude oil. Now I have a Beseler dial thermometer, sometimes it sticks, typical Beseler quality. I wouldn't use a mercury thermometer for day to day work, too dangerous if it breaks.
 
Mercury wasn't "dangerous" when our fourth grade science teacher would let us roll a little ball of it around the palm of our hands with our fingers. We didn't wash up afterwards either. Just eat our peanut butter and jelly sandwiches! It wasn't all that dangerous in the 1960's when we'd salvage our underexposed negatives with Victor's Mercury Intensifier. We'd stick flourescent tubes in the trash can, breaking them so they'd fit. We got exposed to lots of mercury.
 
Al Kaplan said:
Weston dial thermometers are usually pretty accurate. All the dial thermometers that I've seen have a hex nut around the shaft under the dial. Hold that with pliers and you can turn the dial to match the reading on your process thermometer, or other thermometer known to be accurate.
Click to expand...
That's what I use. And, for b/w, it's been a lot better than "close enough for Government work." (It came with my Honeywell/Nikor tanks/reels, so it dates from back then.) It's all been mothballed for a year and a half, but Im about to break it all out again to deal with my backlog of shot film; then, it'll be used on a regular basis again (once I figure out which wall to hang my electric film dryer...it stays upstairs, while the developing goes on in the basement).


- Barrett
 
I prefer Kodak glass and have found them on eBay in good condition but I have several Weston and Beseler instruments. If you buy a metal type, consider investing in a good colour chemistry model; the expanded range is useful, especially when mixing chemistry.

Keeping several gallons of water in the darkroom is something I do, both tap and distilled and it really works well for me. I use the Ilford method for washing film which saves water so I only need to run the tap to clean-up and refill for the next session. No fidgeting with the faucets is just a nice bonus, especially in the summer when the cold tap runs decidedly warm.
 
How about going digital? I picked up a used Fluke model 51 digital thermometer a few years back. Fast response and easy to read in the darkroom. This is the current version... http://www.tequipment.net/FlukeThermo51.html
Mine is an early model that doesn't have all the bells and whistles of the one in the link and only cost $50. Calibration when checked was within 0.1 degrees from 0 to 50 C.

Glenn
 
Ronald, if you are seeing roll to roll inconsistencies, rather than regular over- or under-development, it may not be that your thermometer is off. When you start out cold from the tap water, the solution gradually warms up as your development tank stands in the warm air. So it could go in at 20, while the air is closer to 30. After 5 minutes the developer might come up to, say 24 degrees. After 15 minutes, it might reach 27.

I have overcome this issue by using the air conditioner to lower the house to 24 degrees, and chilling my developer to the same temperature. As there is no differential between developer and air, the temperature of the developer does not change, no matter how long I keep it in the soup.

ps, I use a master and secondary thermometers like Roger suggests. My master is a NIST calibrated mercury thermometer, and the secondary an inexpensive dial one. Contrary to popular fears, metallic mercury is not dangerous. Mercury vapor and organic compounds (and to some extent inorganic compounds) are.
 
Last edited:
For B&W it doesn't matter what kind of thermometer you have unless the reading accuracy is within 1 degree C/F.
For 4-5 € you can buy an alcohol thermometer.

If you're doing color stuff you need a calibrated thermometer and it's cheaper to use a digital one these days. About 40 € you can have one.

An extra (calibrated) thermometer is easy when your regular one brakes so that you know the deviation which you work on. But when your regular thermometer is within 0,5 degrees of the actual value you can forget this remark.
 
You must log in or register to reply here.
Back
Top Bottom