Equation for Tempering a 1:4 developer mix

[JSturr]

For some this ratio/equation may be a no brainer... but to come up with it I had to dig deep with some mental gymnastics.

Tempering a 1:1 D-76 mix is really a no brainer ratio. ((x temperature) + (resting developer temperature mix))) / 2 = 68

Basically you averaging everything out to get to 68 degrees.

But -- I've switched from a 1:1 D-76 to a 1:4 Ilford Ilfotec DD-X.


So -- I looked at the bottle -- looked at my graduated cylinders -- then looked at the bottle again - and when --uuhh.....



This is what I came up with --


I keep all of my chemicals at a resting indoor temperature - and that varies and is never a perfect
68 degrees.


I know I need a 1:4 mix -- 1 part developer and 4 parts water. This whole mixture equals 5 parts.

These 5 parts need to have a a final temp of 68 degrees === 5(68)


Here's the ratio/equation


4(x water out of the tap to temper) + 1(resting developer temperature) = 5(68)


so -- for instance -- let's say my resting developer is 72 degrees and I want a 68 degree 5 part mix.


4(x) + 1(72) = 5(68) x = my needed water out of the tap to temper the 72 degree developer

4x = 5(68) - 72

4x = 340 - 72

4x = 268

x = 268/4

x = 67


So -- 4 parts of tap water needs to be 67 degrees when mixed with the 72 degree Developer to = 68 degree mix.