After anodic bond we had an undesirable roughness or white material on
the surface of the bonded Pyrex.  A solution to this problem was to
place a second Pyrex wafer on top of the Pyrex being bonded.  This
technique worked well for several years, but recently the two Pyrex
wafers have been bonding together.  We're using a Suss BA6 bonder
350-400 degC, 1,000 volts.  (We've recently switched from Pyrex to
Borofloat.)

Can anyone suggest a way to prevent the glass wafers from sticking
together, or alternatively another technique to prevent the unsightly
residue on the surface of the bonded Pyrex?

Roger Shile