Black Marble or slate cases
Wooden cases are covered fully in the range of books onfurniture restoration
available, but marble clocks are fairly unique to the restorer.
There is
no magic chemical formula for restoring a black mirror finish to dulled and
greying slate (actually a limestone). The correct method involves completely
dismantling the case and re-polishing each individual piece with sophisticated
polishing machinery. Dismantling can do more harm than good because the cases
were often wired and cemented together very firmly, and re-polishing requires
special skills. The greyness of the case is the result of years of oxidation,
particularly as a result of the heat from Victorian fireplaces.
Some
'experts' suggest rubbing with fine abrasive paper but you should be very
careful if you do this. Under the oxidised layer is often a coarse material
which will not take a shine easily.
M&P's Slate Blacking is a
compound made especially for this purpose and will normally produce an excellent
finish unless the surface is very grey. To stain marble clocks, it is important
to remember that only a small mount of blacking need be absorbed for it to
work
For a sucessful application, apply the least amount possible. The
product is so strong that the least amount absorbed by the surface should be
sufficent to stain it. Having been left to soak in, remove all the surface with
a cloth.
A final coat of Beeswax Polish should bring a deep black shine
to the surface.
Many marble clocks had fine gilt lines engraved in the
case. In most instances, this is in good condition but under years of grime.
When the case has been blackened, waxed and polished, take a pointed instrument
like a piece of sharpened pegwood and follow the lines. You should find
the grime comes out leaving the original gold showing. If this fails to work,
clean out the grooves thoroughly and gild with transfer gold leaf.
This document is © copyright M&P 2005
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