Developing 35mm Film

[pentaxuser]

In a nut shell, the correct calculation takes into account the different heat capacity of different substances. Heat capacity is "the amount of heat to be supplied to an object to produce a unit change in its temperature" (link to Wikipedia). In other words, the amount of heat energy released by substance A when its temperature is lowered by 1 degree isn't the same as the heat energy needed to raise the temperature of substance B by 1 degree if substance B has a different heat capacity. Therefore the final stable temperature wouldn't simply be the mean value of the 2 initial temperatures.

Thanks. I manged to gather that much from the link It was the formulae that made my head spin but essentially I was hoping to find out from those who know understand the formulae what the end result might be compared to the way that the poster attempted to get to 20C from 150ml of water and 150ml of water in which he had stock developer

From that I can decide if the method used which is the one I'd use, is good enough or not good enough to use in the future

pentaxuser

 

[RalphLambrecht]

May I suggest on the best method I have so far encounted to develop 35mm film?



If you develop film at 1:1 in D76 or other developer, can I suggest the following method of preparation? Assuming you’re using tap water as part of your developing solution and not distilled or deionized water, this method is fairly easy.



To make a 1:1 developing solution for one 35mm film, you will need 150ml of water mixed with 150ml of developer = 300ml (I know it says 290ml on the tank, but 300ml and its division by ½ to 150ml is easier to remember). This mixture of developer and water should ideally be at a temperature of 68F/20C.



Pour 150ml of developer into a measuring jug and measure its temperature. If it is under or over 68F/20C, make a separate jug of water to compensate for the difference. Example if the developer temperature is 18C, make the water to 22C, before adding 150ml of developer.

To get the water at the required temperature, put a thermometer in the empty jug and add hot and cold, either from two separate taps or a mixer tap. Don’t worry about the quantity as you can let the excess flow over the edge, just concentrate on getting the temperature you require, in this case 22c.Then pour out the excess to leave 150ml and then add to the developer, thus achieving a developer solution at 68f/20c.



And never ever, ever after the film is fixed, washed and dryed, use a squeegee. Let the film dry naturally overnight in a bathroom or airing cabinet.

If others can suggest a better method, I would like to learn about it.

It's a logical method and the one I use for decades with my Jobo tanks but really nothing new

 

[Don_ih]

really nothing new

If we only talked about new things, we'd be pretty silent.

 

[Tom-Thomas]

Thanks. I manged to gather that much from the link It was the formulae that made my head spin but essentially I was hoping to find out from those who know understand the formulae what the end result might be compared to the way that the poster attempted to get to 20C from 150ml of water and 150ml of water in which he had stock developer

From that I can decide if the method used which is the one I'd use, is good enough or not good enough to use in the future

pentaxuser

Without knowing the heat capacity of the 2 liquids, one can't calculate it, but I believe the OP said that from his own experience the end temperature is close enough to the mean value. I'll take his words for it. (I wasn't trying to challenge OP's method in my post. I just want to put it out there for clarity.)