I saw the article in American Antiquity and it was my take on it that the
Calgon method relieved the burden of having to scrub, thereby eliminating
damage to microwear patterns, etc.

Also, the authors do mention that objects with obvious staining (burned
ceramics for example) would not be subjected to this cleaning method.

Some sites *must* be wet screened and I don't see how the Calgon method could
be any more detrimental than wet screening...

I did wonder about pollen, blood residue, or pigment, but I can think of other
ways to test for these types of samples, including processing 10% of the
excavated materials differently than either Calgon or screening.  Of course
some artifacts so obviously will yield information on pollen or residues and
probably wouldn't be subjected to screening in the first place...

My two cents,
Paula Johnson
Paragon Research Associates
Seattle, WA USA