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# Thread: Development of 35mm film

1. ## Development of 35mm film

Can I suggest a method of development that APUG members may agree or dissagree and if so, suggest a better method for development of 35mm film?

The method I use (assuming you are using dev at 1:1) is one I picked up some years
ago and although I once used water jackets and such like, but 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 water to the 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 differential you require. Then pour out the excess to leave 150ml and add to the developer in the separate jug.

Thus, you have 300ml of developing solution at 68F/20C.

2. May I also throw something else into the mix? As taken from Covington's excellent XTOL page:

New time = Old time * exp(-0.081 * (New temp °C - Old temp °C))
New time = Old time * exp(-0.045 * (New temp °F - Old temp °F))

And this holds pretty accurately for similar developers. It is not strictly required that development proceed at 20C.

3. I always keep a couple of half-litre bottles of tap-water in the refrigerator for making cold water-baths.
A hot water-bath is easy: Hot tap-water.
Thus, it's a simple matter to bring a developer to 20C from either direction.

Mark Overton

4. I pour my developer into a beaker and take the temperature. Then I slowly stir in hot or cold water until the solution is at the desired temperature. I use hot (very warm) tap water or ice water if my tap water isn't cold enough.

Using the same method, I make another beaker of plain water that is at my desired temperature. Finally, I top up the beaker of developer solution with the tempered water I just made.

This way there is no math involved. Just make sure the water you add to your developer solution is significantly warm or cold enough that you will have it up (or down) to the right temperature before you reach the volume you need.

If you miss you can put your beaker of solution in a bath of hot or cold water and stir until it reaches temperature. Just make sure you stop a little early to account for the thermal inertia created by the container. In my case, using a glass container, I stop about one degree early. The temperature difference between the glass and the solution will allow it to "coast" to the right temperature once I take the container out of the water bath.

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