Differing densities of chemicals in developer solutions?

[evan_parker]

I've recently noticed that, depending on where I measure the

temperature of my developer solution in my graduated cylinder (as in,

how deeply the probe is submerged), the temperature can vary by up to

one degree Fahrenheit.

 

My method of creating the developer solution (in this example, D-76

1:1) consists of pouring out one part of D-76, measuring it, and then

adding an equal part of water at a temperature that will bring the

entire solution to equilibrium (say, 65 degrees F). I stir the

solution thoroughly, and then measure the temperature. I've found

that, near the "top" of the solution, the temperature is warmer, and

near the "bottom", the temperature is considerably cooler.

 

I realize that hot water rises. My question, however, is this: do

developer solutions and water have signigicantly different densities

to create a thermal inequity like this, or is this just the warmer

liquid rising to the top? Will stirring suffice to equalize the

temperature? Will this thermal/density problem manifest itself again

in the tank, where they will again seperate?

 

One more question: For some reason, using identical developers and

films, when I dump the developer it is significantly more tinted with

color than other times using the same materials. However, I have

observed that significantly more "dye" (is this antihalation layer?)

washes out at higher temperatures (such as the 75 degrees that seems

to be optimal for TMAX films). Is this due to the exposure on the

film enclosed, thermal variances in the developer, etc.?

 

Thanks very much for your time.

[conrad_hoffman]

Don't know what kind of thermometer you're using, but good lab thermometers are either "total immersion" or have a specific immersion line engraved on them. You are probably seeing the thermometers sensitivity to immersion, rather than a difference in the stirred liquid. Unless otherwise marked, use the maximum immersion possible.