View Full Version : Rules of emulsion making

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01-21-2009, 02:58 PM
So on the chart that shows crystal shape vs. pAg, it states that this is at 70 C, does the temperature also effect grain shape, As in if we do the addition at 40C, do we need to raise or lower pAg for the given crystal shape.

Photo Engineer
01-21-2009, 03:30 PM
As noted elsewhere, temperature affects the size of the crystal and the rate of digestion/ripening.

Salt affects pAg and therefore the crystal habit. The chart is for Bromide.


Kirk Keyes
01-21-2009, 04:54 PM
Note that Ksp changes with temperature.


Photo Engineer
01-21-2009, 06:57 PM
From the Nernst and Debye Huckle equations one can get to the vAg. Here is the pKsp calculation for Bromide ion as a function of Temperature.

brpksp = -12.1258 + 5868.64 / (T + 273.15) + .015953 * (T + 273.15)

The patent is very early work, but useful. The latest was published in the 90s IIRC.


06-11-2009, 01:50 AM
After reading #4, is it correct in assuming that #6 in this website (http://unblinkingeye.com/Articles/Emulsion/emulsion.html) is incorrect?

Ray Rogers
06-11-2009, 02:53 AM
After reading #4, is it correct in assuming that #6 in this website (http://unblinkingeye.com/Articles/Emulsion/emulsion.html) is incorrect?


(but what #4 do you referr to? PE's #4 in post #1 or Ian's Post #4? Well, either way.... speaking in general terms, there is no real conflict here. What did you have in mind?)

Photo Engineer
06-11-2009, 09:06 AM
The item #6 at Unblinkingeye is a specific case. Addition time and rate will determine the characteristics of an emulsion.