A lifetime of learning indeed. I wish I could tour Kodak or Ilford and see how they actually test these things.

On the subject of the additives to prevent image spread, what are the implications when it comes to the acutance of stained/tanned negatives? This has always confused me. I've mentioned this before but would be interested in your thoughts. Formulators of modern staining formulas make certain claims:

1. Less graininess than non-staining high acutance developers due to lower silver densities. Makes sense to me.

2. Less graininess than non-staining high acutance developers and "smoother" tonality, both due to the dye filling in the spaces between developed silver particles (ie grain masking). Perhaps correct - but this is image spreading, so if this is the case to any significant degree, resolution and acutance must be degraded.

3. Tanning results in a somehow more precise development and formation of silver, limits the effects of irradiation, and limits diffusion. If tanning limits diffusion, does it limit diffusion of the developer, bromides, oxidation products/dye, all of these or some of these?

There appear to be some inconsistencies in the common descriptions of how these developers actually work - sort of like having your cake and eating it. For example, the developer gives high resolution and acutance, and more precise high density development due to low diffusion, but also encourages pronounced edge effects and masks graininess due to dye spreading (implying diffusion). And in colour systems it would seem attempts are made to prevent dye spreading.

Unfortunately these mechanisms are not discussed in great detail in volume I of Haist. Tanning developers are discussed mostly from the point of view of relief images.

As an aside, I hadn't noticed this before but there is at least one reference to one of your patents in volume II of Haist.