Bob Yankle Loc: Burlington, NC

I had mentioned earlier I thought this was in the "High Key" family of processing. I toned down the contrast quite a bit and edged off on the clarity, vibrance, and even a touch of saturation. But that is only my interpretation. I hope that a few other folks take a stab at it because I'd surely like to know how they did it. Notably, Topaz Impression does not have a Sfumato preset, so there does not seem to be a one-stop fix if one tries to emulate this style.

On the other hand, it DOES have a Da Vinci Sketch preset which has some of the same characteristics. See below:

Bob Yankle Loc: Burlington, NC

Dave, rather than explain how I did it, I'd like some other folks to publish their own interpretations (right now I don't think we have any "experts" on this effect to it would be good to discover a number of different paths to arrive at the same point). Interestingly, though, I'd read your description about applying an earth colored pigment (green or brown) to an already finished pieces. The last step in my process was to apply an Image>Adjustments>Camera Filter>Sepia adjustment layer, then dialled back the opacity to approximate your "pigment over paint" effect.

Uuglypher Loc: South Dakota (East River)

Thanks, Bob,
Exactly the sort of info I'd hoped for...and, as expected given the source, eminently logical!
Dave