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1. ## Chillin...

OK, in this part of the country (North Texas) and many other parts of the Southwest and South the water temperature is pretty dog gone warm. Yesterday I processed a roll of film and the water temp out of the tap was 80 F.

Question #1 - why are most standard times based on 68 F? Do the guys in the lab think this is an average temp. for most people (and for that matter is it?)?

Question #2 - for those of us in these environments, how do most of you adjust your temp? Or do you adjust your developing time instead? Not really a big issue, just one of those things that make you go Hmmmmmmm!!

Thanks,

2. Depending on who you ask, room temperature is usually defined as between 68 and 72 degrees (F). I have always assumed that 68 degrees was selected for this reason. I know many people that use 70-75 degrees as their standard developing temperature. I have the same problem here in Indiana. My tap water temperature is between 70 and 75. My method is simple. I keep some water in jugs. With the AC, room temperature is about 70 degrees. I also make sure that the water bath has a large volume of water and is at the right temperature. Using a large volume of water means that I will see very little fluctuation. I also have a Jobo ATL. It has a chiller line that obviously won't work if the temps are too high. Thus, I often drop a few ice cubes in the water bath to lower the temperature. In this case more is better than less as the Jobo will bring the temperature up quite easily.

Jimmy Buffet has a new album called: License to Chill... It's in my CD player now!

3. It is quite easy for me here in the swamps of the eastern shore of Md. I arrange a water bath with a piece of Rubbermaid tub roughly 14"x18"x10"deep. I cool the bath to about or slightly lower than 20 deg.C. with ice. I chill the developer to the same with a small piece of ice in a commercial plastic water proof bag. This keeps the water from diluting the developer. All the chemicals in Quart "Mason" jars are placed in the bath. There is sufficient volume of water in the bath to keep the temp under control throughout the processing. during the development I keep the tank (or whatever) in the bath after agitation. When complete, I begin washing with the water from the bath then later, maybe, do a rinse in the tap water prior to the final rinse with distilled water + home made Photoflo!

4. I think that somewhat chilly standard was set back when film emulsions were quite a bit more delicate than what we have now on the most part. The older emulsions had a tendency to soften and dislocate when processed at overly high temperatures. You will see some of the older processes that had hardening steps to help alleviate that, the most recent being the hardening fixers like Kodak Rapid Fix with it's optional hardener. I remember the old E-4 process which ran at about 100F had a hardener as it's first bath.

5. Originally Posted by DrPhil
Depending on who you ask, room temperature is usually defined as between 68 and 72 degrees (F). I have always assumed that 68 degrees was selected for this reason. I know many people that use 70-75 degrees as their standard developing temperature. I have the same problem here in Indiana. My tap water temperature is between 70 and 75. My method is simple. I keep some water in jugs. With the AC, room temperature is about 70 degrees. I also make sure that the water bath has a large volume of water and is at the right temperature. Using a large volume of water means that I will see very little fluctuation.
I follow the same basic procedure as DrPhil - I keep several large (and small) jugs of water in the lab, which is both humidity and temperature controlled at 70F, plus or minus a degree.

For most B&W developing chemistry 68F (20C) is in the "sweet" portion of the "rate of chemical reaction" curve. For most processes, you can go up or down a few degrees from 68F in a very predictable fashion (with respect to required developing time).

If the processing temperature gets too high, the developing times get very short, thus small timing errors have a larger effect.

If the processing temperature gets too low (near the chemical reaction threshold), development may not occur at all.

6. Here in Florida my tap water seldom drops below 80F/29C and I don't have a good way to chill the large quantities of liquid I use with minimal agitation and 8x10 negatives. Also, there's the impossiblity of getting the wash water cool. I've found that if I do develop and fix at 20C, the 29C wash water caused pin holes.

For those reasons, I've standardized on 80F/29C for that process. The higher temperature seems to not matter and, in fact, it makes the long development times a bit more convenient.

With tray/brush develoment, 80F/29C is just too hot - development times are too short. I'm working out a process of chilling the developer and fixer to 20C, then chilling the first wash water with ice in a tray. Leaving the film in the tray, it gradually warms and further washing is with the 80F/29C water. As I say, I'm still experimenting with this.
juan

7. 20°C is the standard laboratory temperature - for ANY kind of laboratory work. If no other temperature is stated, 20°C is implied. This has been the standard ever since the idea of standarization first crossed a lab-workers mind.

It probably originated in north west Europe...

8. Here is what i do. Put ice in a zip lock and place it into the developer for a bit. The large surface area will remove heat from the liquid at a faster rate. Stir the chemicals while the bag is in it and them check the temp often. Remove zip lock and toss in the trash or rinse it off and pitch it back in the freezer for when the temp begins to rise again.

In my mind, this is easier than adjusting development times.

9. You are spoiled. In the country, where water comes from wells and cisterns, it must be warmed to 68 F even in summer. Mechanical refrigrators for the home were invented after the photographic process. Things were kept cool in a cellar house dug into the shady side of a hill or below grade. Ice from ponds and lakes was cut in winter and stored in sawdust through summer. Why, when I was a child.... In other words, I don't know why 68 F is standard, but that won't keep me from letting on like I do.

10. Ole is correct, I work in a metrology lab and 20°C is considered the standard temp for all types of measurements. For example, steel gauge blocks (length standards) are at the nominal value at 20°C, anything else requires correction. Same for standard pH and conductivity solutions, and a multitude of other items. So it is safe to assume that the 20°C standard was probably used by the folks doing the original ASA tests for film speed.

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