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Go Back   APUG > APUG English Forums > Darkroom > Silver Gelatin Based Emulsion Making & Coating > Rules of emulsion making


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Old 01-21-2009, 01:58 PM   #21 (permalink)
 
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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.
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Old 01-21-2009, 02:30 PM   #22 (permalink)
 
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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.

PE
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Old 01-21-2009, 03:54 PM   #23 (permalink)
 
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Note that Ksp changes with temperature.

http://www.google.com/patents?id=iac...um=2&ct=result
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Old 01-21-2009, 05:57 PM   #24 (permalink)
 
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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.

PE
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Old 06-11-2009, 12:50 AM   #25 (permalink)
 
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After reading #4, is it correct in assuming that #6 in this website (http://unblinkingeye.com/Articles/Em.../emulsion.html) is incorrect?
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Old 06-11-2009, 01:53 AM   #26 (permalink)
 
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Quote:
Originally Posted by EASmithV View Post
After reading #4, is it correct in assuming that #6 in this website (http://unblinkingeye.com/Articles/Em.../emulsion.html) is incorrect?
No.


(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?)
Last edited by Ray Rogers; 06-11-2009 at 02:08 AM..
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Old 06-11-2009, 08:06 AM   #27 (permalink)
 
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The item #6 at Unblinkingeye is a specific case. Addition time and rate will determine the characteristics of an emulsion.

PE
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