Constant temperatures

How do those of you that develop your own negatives keep a constant temperature of you chemicals. I have read using a water bath to keep each chemical warm. But how hot of water does one use to keep a constant say 68F. Sorry but my brain only works in Standard units so C makes no sense to me. I am slowly working to doing my own and want to get all the info that I need in my head before I start.

You may be thinking too hard about this. What temperature is the air in your working area? It probably is about 68F.

One of the reasons that 68F is used so often in black and white so often is that it is a common room temperature. If the air temperature in a room is close to 68F, than your chemistry will generally settle on that temperature too.

The idea is to have your chemistry at room temperature, and then adjust your development time slightly to adapt to that temperature.

Are you working in a particularly cold environment? If so, it may be necessary to use water baths and the like to temper the chemistry, but that would be a relatively rare circumstance.

I do note, of course, that your avatar is a penguin. Are you, by chance, posting from Antartica?

Matt

I guess you are right. It is just that every book I have read about photography and development makes a point about a water bath.

Well a water bath is one way to keep the temperature constant. However, I mix my chems at 20C, and don't worry about the temperature drastically changing in 6-8 minutes, because the ambient temperature is somewhere around 20C.

marsbars said:

I guess you are right. It is just that every book I have read about photography and development makes a point about a water bath.

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There are definitely times when tempering baths are necessary, such as when:

1) the target temperature is very different from a typical ambient temperature; or
2) the ambient temperature where you are is very different from 68F.

For an example of the former, consider some of the colour processes, which are designed for higher temperatures (100F for example). In that case the difference between the ambient temperature and the target temperature for the chemistry makes something like a water bath necessary.

For examples of the latter, try a search through the threads here, where you will find threads dealing with areas like the tropics which are too warm for easy development near 68F - there you need cooled water in your water bath.

In 40 + years I've never had to use a tempering bath for black & white, but that's because I've always been able to work in moderate conditions.

Your right though to ask the question, because I have seen many references to tempering baths, its just that they are intended to deal with slightly unusual circumstances.

Have fun, and don't hesitate to look through APUG for answers. If you cannot find them, feel free to ask more questions.

Matt

I've never used a water bath either for over 25 years. My darkroom air temperature ranges from around 16c to 26c depending on season. I don't prewash film or mess around with the tank. Once you pour developer into the tank the temperature changes. In summer I start the developer around 18.5-19c and it generally warms to around 20c in the first minute. In winter I start at around 21c and it cools to around 20c.
I generally check the temperature after the first minute and then halfway through the nominal development time. If you are doing intermittent agitation simply pull off the cap on the tank and stick in the thermometer for 15 seconds at around the 4 or 5 minute mark. This will tell you if the trend is towards warming or cooling and then just extend or shorten time accordingly.

Bottom line is don't fret about it. Shoot and develop lots of film. Make lots of prints, keep good notes and adjust as you go. Try to stick to one film and developer initially until you have a robust, reliable set of habits. You can then go an all sorts of adventures from there if you are so inclined.

As a good friend keeps reminding me 80% of the worlds great photos were TriX/D76/Dektol!

I do the same as Tony i.e. start a bit warmer in the winter and a bit cooler in the summer.

I don't worry about the temperature of the stop (plain water) or fixer. Whatever comes out of the cold tap is all I use.

Obviously, if your water supply is significantly hotter or colder than 20 degrees you will want to mix your stop and fixer to be around 20 degrees but no real accuracy is required for these two solutions.


Steve.

Storing the dev tank in water at 20.C (68F) during processing is often mentioned but don't worry about it too much.

I use a presoak in water at 68F for other technical reasons but it does bring the temperature of the plastic tank to the desired temperature for even development. If I don't presoak I aim for 20.5/ 21.C

Thermometers are not exactly accurate to start off with, so just make sure the numbers on the film rebate are dark grey/ black after processing.

My Zone VI compensating timer has a temperature probe and adjusts time to simulate 68 degrees. These show up on the auction site with some frequency.

My darkroom has been operating again for six months and the temp has ranged from 64 to 71 degrees in that time. So that's been room temp for stock solutions.

With a water panel with a temperature regulator, I mix working solutions with 68 degree water, then run a 68 degree water bath at a trickle.

I only use a water bath for colour.

For B&W if it's cold enough to matter the furnace is on. If it's hot enough to matter the A/C is on. B&W is forgiving enough that the numbers don't have to be exactly 68F. How much more development would you really get at say 75F?

You have to be careful with this. If you live in, say Arizona, and your summer 'cold tap' water temp is 90*F, that could change things around a bit.

- Thomas

Steve Smith said:

I do the same as Tony i.e. start a bit warmer in the winter and a bit cooler in the summer.

I don't worry about the temperature of the stop (plain water) or fixer. Whatever comes out of the cold tap is all I use.

Obviously, if your water supply is significantly hotter or colder than 20 degrees you will want to mix your stop and fixer to be around 20 degrees but no real accuracy is required for these two solutions.


Steve.

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Consider Kodak Darkroom Dataguide calculator

Found in old Kodak darkroom guides is a circular calculator that has development time on one wheel, and temperature on the other wheel. They rotate to allow a specified time at 20C/68F to be lined up. On one other part of the wheel is a development number DN scale, and markers for -50 to +150 % develpment, if I recall correctly.

I keep stock solutions at room temp, and stock boiled cooled and stored reverse osmosis water jugs at the same temp.

For an example that I can recall: TMAX100 in FX37 diluted 1:3 works well for me witha DN of39 to give a negative that prints well for most subjects onto a grade 2 enlarging paper. This means something like say 8 minutes at 20C. But all I do is stick a thermometer in the mixed solution, and read the temp that the mix is actually at - then look at the dial calcualtor when the outer and inner dials are lined up for DN39 marker opposite the 0% development extension marker. The time/temperature part of the claculator tells me how long to set the old Gralab 300 timer for chemistry mix that I have at the moment.

If I know that things are going to be too fast (less than 5 minutes in a small tank and a meaningful part of the time is occupied filling and draining a stainless daylight tank) ie both stock and mix water is warmer than 20C then I might resort to dropping one part of the mix water with a reverse osmosos/distilled water ice cube. Usually I only do this if I have let the stock solution run out and want to develop the film with a still cooling just mixed developer stock solution.

If I know that things are going to be too slow (my darkroom can get down to 16 in the later part of Febraury) I put the mix of developer and stock into the microwave that I have nearby to speed drying of FB paper test prints, and warm it 20 seconds at a time until the temperature approaches 20C. That way the tank is not too cold to want to hold for something like what might be needed for an 18 minute developer period with some 35 inversions.

I get amused when someone refers to 68 F as standard temperature.

The good ol' USA is still stuck using degrees F, Miles, Inches while the rest of the world uses those non-standard metric things.

More people use metric than English units now.

No offence meant, just an amusing side venture to me. AAMOF, Kodak used mg/ft square, an obscure mixture of both systems in coating. What a world.

BTW, the 98.6 body temperature in deg F is an accident. The originator of the system wanted body temperature to be 100 F. His test subject had a fever that day and that is why the odd result perpetuated to this day. And, as another side note, the thermometer was invented about 200 years before vaseline. So humanity suffered a very painful indignity for 200 years before they could ease the taking of a body temperature. (think on that for a bit and then laugh with me)

PE

Tony Egan said:

I've never used a water bath either for over 25 years. My darkroom air temperature ranges from around 16c to 26c depending on season. I don't prewash film . . .

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I adjust development time for B&W negatives and prints to accomodade darkroom temperatures from about 65 to 85 degrees F. Wash water for negatives and all chemicals are stored at room temperature. A prewash is used if negative development is shorter than maybe 5 or 6 minutes. This isn't really precise, but works for me. Many other methods are as good and usually better. It's the finished print that really matters, not the route taken to get it.

Mike Wilde said:

Found in old Kodak darkroom guides is a circular calculator that has development time on one wheel, and temperature on the other wheel. They rotate to allow a specified time at 20C/68F to be lined up. On one other part of the wheel is a development number DN scale, and markers for -50 to +150 % development, if I recall correctly.

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Well, finding an old Kodak darkroom guide might be a bit problematic for some. Short of finding one on eBay or at a garage sales, they are not commonly available. However, there is an alternative published by Ilford that is freely available here: http://www.ilfordphoto.com/Webfiles/2006210208211880.pdf. I use it and find that it is quite accurate by my judgment for commonly used PQ and MQ developers.

I do use a water bath with an immersion heater to stabilize temperatures for film development, but don't bother at all for prints. Winter time temperatures in my basement darkroom can fall to 55F, and cold tap water can drop as low as 49F at times. In summer, the temperature is closer to 75F with cold tap water coming out at around 70F. So for my purposes, 75F works out well.

I have had to suffer no consequence from ignoring ambient temp during B&W film development (or paper as far as that goes) I will not let the film jump more than 4deg F between baths though. Drastic jumps in temp from developer to wash and to fixer will cause reticulation and even cause the emulsion to separate! I store 50 gallons in my darkroom at ambient temp - which in my house is 68 in the winter and 75 in the summer. - All my water stays in this range - mostly around 70 or 72F. All my fluids are normalized at this temp. I adjust development times if I need to.

With Diafine I don't worry about temperature...one of the cool things about that developer is the ability to give like results at a range...but with Rodinal I mix at 68 degrees and then forget it. My house usually stays around 75 degrees and, interestingly enough, I measured my chemicals at 68 degrees regardless of that. Go figure.

For tank development, temperature drift during development is usually not an issue, but if you have a quarter inch depth in an 8x10 tray, and the humidity is 30%, expect it to cool off dramatically, eventually reaching something like 50 F. This can happen in a few minutes, if air is moving quickly over the tray. The smaller surface-to-volume ratio in a tank keeps this from becoming a problem, as the change of temperature is much slower.

A couple of degrees Fahrenheit is not much of an issue, unless you are working right at the edge of b-up in the highlights; then it is.