Some months ago there was a thread wondering about the thick black
oil-like substance that can form in magnetic tumbler. For some reason
that thread stuck with me? Anyway, I have an observation on this
topic to share.
For years I have used "Soap Powder for Magnetic Tumblers' from
Gesswein #852-1039. You just put a tablespoon of the powder in the
water. The water would eventually turn black but there was no oily
black substance. More recently I needed to replenish the pins in my
MT and so I bought some from Otto Frei (a great company). I was low
on soap so I also bought the 'soap' OF sells, which is a liquid, (MF
610, part #147.773). It's described as a mildly acidic cleaner
containing special lubricating additives. etc.
What I found was that the OF liquid eventually would leave the
somewhat thick black sludge like deposits in the bowl and on the
pieces. The Gesswein soap never did that. My thought is that it may
be the lubricating additives in the liquid, but I don't know.
So concludes the observation. Mark