wrote in message
...
On Thu, 03 Nov 2011 07:18:55 -0400, Doug Miller
wrote:
On 11/2/2011 11:51 PM, wrote:
I use a fair bit of acetone. I have always accepted that it leaves a
bit of an oily residue. Recently I have been finding a *lot* of oily
residue. Is it just a rogue bottle or has anyone else noticed this? If
so is the likely cause cutting costs during production?
Acetone evaporates almost instantly, and leaves *no* residue. If you're
seeing any oily residue at all from acetone, it's not pure. Bitch at the
supplier.
What specific product are you using, so I know what to avoid? :-)
This can came from HD. It is not a problem really as I have been using
a two-stage procedure for degreasing for some time now (that is if I
need a *really* clean item - has to pass a waterbreak test).
It's just that the amount of grease in this last can was more than I
remember previously.
BTW I find proper degreasing another one of those Black Magic
procedures: You have to do it right before the next process, you
cannot do it a day in advance. You also cannot do Stage 1 one day and
the Stage 2 the next day. Why? Lord knows...
Michael Koblic,
Campbell River, BC
A really clean metal or glass surface has a great affinity to attract
hydrocarbons out of the air. I used to design optics for instruments that
measured film thickness on silicon wafers. These were sensitive enough to
detect a average thickness change of less than 0.1 angstrom (yes, this is
less then the width of an atom, but that much of a change would just mean
that a few extra molecules are sprinkled over the measurement spot). In
any case, you could take a freshly cleaned silicon wafer, put it in the
machine, and watch over the next hour or so as a monolayer or two of
hydrocarbon attached itself to the surface. You could then heat the wafer on
a hot plate and drive off the hydrocarbons again. High vacuum equipment is
usually baked at low pressure before installing to get rid of hydrocarbons
and water.