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