Digital BW, The Print

I'm a big fan of Mark's work, especially the images created
with the plungercam. I have seen several images lately that
have a sort of texture or uneven quality to them.  The "Happy
House" on the front page of his site today is a good example
of what I'm trying to explain. Is this achieved through the hand 
coating process that has been discussed previously?  If so, is
this done with several uneven coats? Just curious, Thanks.

Doug Santoli