SPI Carbon and Graphite Rods for Evaporation
How to determine what it is that you have been using
It is not at all unusual for a user of so-called "carbon" rods to have to
re-order but does not have the slightest idea as to whether the rods are
really "carbon" or whether they are graphite. Indeed, the rods are more
likely to be graphite but many firms selling "carbon" rods are really
selling graphite instead. And if you purchase carbon when in fact you have
been using graphite (or vice versa) then you will find the performance
of the rods to be quite different from what you had been experiencing.
So we present here the "SPI test for rods". Take the rod you have been
using, and pick it up like a pencil and try "writing" with it like you would
a lead pencil. Does it tend to write like a pencil? If the answer is "yes",
then it is probably graphite. Indeed, so called "lead" pencils are really
all graphite and never carbon. Writing is possible with graphite because,
relative to carbon (that has not been graphitized), it has a layer-like
structure, and in fact is the reason for its slippery like structure, and
indeed is also what makes it useful as a dry lubricant. So one is able to
"write" with a "lead" pencil made out of graphite but they could not do that
if the "lead" in the pencil was carbon.
But if the rod tends to dig into the paper, and tears the paper when you try
to "write" with it, then it is probably carbon.
Of course, there are other factors that could distort this test, such as
wide extremes in the density, but as a first "rule of thumb", this test is
generally valid.
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Sunday March 21, 2010
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