[pure-silver] Re: Grain Size


----- Original Message ----- From: "Ralph W. Lambrecht" <info@xxxxxxxxxxxxxxxx>
To: "PureSilverNew" <pure-silver@xxxxxxxxxxxxx>
Sent: Wednesday, October 25, 2006 6:26 PM
Subject: [pure-silver] Grain Size


I'm confused by a discussion in a German forum and also by some text in
Ansell/Troup.

Does a higher developer dilution (compensated by an extended developing
time) increase or decrease grain or granularity?





Regards



Ralph W. Lambrecht

http://www.darkroomagic.com


Older books explain the difference in developers when diluted as being due to salt effect, the solvent effect of Sulfite, and pH. According to Ryuji Suzuki, these explanations may not be completely valid. In particular, the effect of "grain clumping" due to emulsion softening may not be significant with modern, highly hardened, emulsions.
The effect of dilution seems to depend on the formulation of the developer. High sulfite developers, for instance, D-76, D-23, D-25, and others, become _more_ grainy as they are diluted. Some relatively low sulfite developers of relativelly high pH, such as Rodinal, become _less_ grainy as they are diluted. The old books attribute the grain of Rodinal and similar developers partly to grain clumping but it must also be due to the activity of the developer and the shape of the crystals developed from the halide. The sulfite in high sulfite developers tends to produce filementary crystals. Under the electron microscope these tend to look like little bunches of steel wool. More active developers tend to develop silver crystals that are shaped like the halide crystals they come from. Since the actual silver crystals are microscopic visible and printable grain are actually due to the combination of many crystals in the emulsion. The shape of the individual crystals evidently affects the way they combine statistically to produce both image and grain.
So, the answer to your question is _both_. Developers like D-76 become _more_ grainy when diluted, Developers like Rodinal become _less_ grainy. There are probably some developers whose graininess is not affected by dilution.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 

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