Dan Marcel has a great idea!  And so close to home I didn't even think of
it!!  My wife is a potter who fires bisque and glaze kilns every few months.
It wouldn't take much to put a few sherds of green edged ware in the kiln.
Having said this, approval from the boss is in no way certain.  She may not
want foreign matter in amongst her work.

But, might we already have an answer?  George, do your colleagues in
production research have an idea of the likely original range of firing
temperatures for late 19th century ceramic goodies??  And how about you
pyromaniacs: any idea what temperature a nice, roaring  house fire reaches?
It must be pretty high and sustained to alter the glaze and/or body color,
right.