Original poster: Ed Phillips <evp-at-pacbell-dot-net> Tesla list wrote: > > Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com> > > Hi, > > "I" have heard it is either finely crushed sand (silica) or just baking > soda. Nothing "high tech" in any case. Some just have "nice" sand in them... > > Cheers, > > Terry Borax was also used, but I don't know why. Ed