The Sun.
London, England, 1834-11-15 00:00:00

SUBSTITUTION OF BLACK LEAD FOR OIL

Every one is acquainted with the effect produced by
oil or grease in diminishing the friction of those pieces
of machinery that are in common use ; a stiff going
clock and a creaking hinge are both rectified by the
application of a few drops of oil. But by long expo-
sure to the air oil is more or less changed, it becomes
rancid and thick, and an acid is developed which cor-
rodes, and therefore injures more or less, the surface of
brass, copper, or steel, with which it may be in con-
tact. It also detains all those little motes or filaments
with which the air of inhabited places is filled that may
happen to touch it, and thus in no great length of time
becomes foul and requires to be renewed. All those
instruments that .by the equable revolution of their
parts are intended to measure the lapse of time are
seriously effected in the regularity of their going by
the progressive thickening of oil, by which the pivots
and other rubbing parts are lubricated. Attempts
have been made, but with no very great success, to
retard this tendency of the oil to decomposition, and
in the higher priced clocks and chronometers the use
of oil has, to a certain degree, been dispensed with,
by making the caps and holes in which the steel
pivots turn of ruby, or other hard and highly polished
gems. Still oil or something equivalent to it must be
employed in some parts ; and in proportion as the
mechanism of clocks approaches nearer and more near
to perfection, it becomes of increasing importance to
avoid the use of a substance that cannot be employed
without introducing a cause of error, always increasing,
until it seriously affects the rate of going, and renders
it necessary to take the instrument to pieces in order to
clean it and renew the oil. Plumbago, or, as it is usually
called, black lead, is a soft unctious-feeling substance,•
which readily takes a high* degree of polish, and there-
fore is well qualified, when interposed between two
rubbing surfaces, to diminish greatly their mutual fric-
tion ; it is also perfectly unalterable by exposure to air,
has no chemical action on substances at any atmospheric
temperature, and readily adheres, by a slight degree of
rubbing, to any surface to which it may be applied.
Mixed up with oil, it has occasionally been used for lu •
bricating machinery ; and it is understood to be the chief
ingredient in the anti-attrition paste that is applied with
good effect to the axles. of carriages. But even the
finest plumbago, such as is used for the best black lead
pencils, contains certainly gritty particles, which wholly
prevent it being applied in its natural state to reduce the
friction of delicate clock-work. It is therefore sub-
jected to repeated grinding and washing over, in order
to separate all its impurities; and is then applied in
a state of powder, or mixed up into a soft mass with
a drop or two of pure spirit of wine. It readily adheres
to the surface of a steel pivot, as well as to the inside of
the 'hole in which it runs, so that the rubbing surfaces
are no longer one metal upon another, but plumbago
upon plumbago. These surfaces, by their mutual
action, speedily acquire a polish, only inferior to that
of the diamond, and then the retardation of the ma-
chine from friction is reduced almost to nothing, and
tear and wear from the cause is totally prevented. An
astronomical clock, of which the pivots and holes and
teeth of the escape-wheel had been covered on their
rubbing parts with plumbago fourteen years before,
was taken to pieces by the Committee of the Society
of Arts ; the surfaces of plumbago were found to be
for the most part unbroken and highly polished, and
neither the pivots nor sockets appeared on examination
with high magnifiers to have undergone the slightest
degree of wear. It is evident that plumbago may be
applied with equally good effect to other pieces of de-
licate machinery besides clocks. For this substitution
of plumbago or black-lead instead of oil in diminishing