‘Many years ago,’ says Mr W. Mathieu Williams, in the _Gentleman’s
Magazine_ for March, ‘when the electrotype process was a novelty, I
devoted a considerable amount of time and attention to the reproduction
of medallions and other plaster-casts in copper by electro deposition.
This brought me in contact with many of those worthy and industrious
immigrants from Bagni di Lucca (between Lucca and Pisa), who form
a large section of the Italian colony of Leather Lane and its
surroundings. These Lucchesi are the image-makers and image-sellers,
and general workers in plaster of Paris. Among other useful lessons I
learned from them was the use of the so-called Dutch rushes, which are
the dried stems of one of the most abundant species of the equisetum
(_Equisetum hyemale_) or “horse-tail,” which grows on wet ground in
this country and Holland. It is well known to practical agriculturists
as a tell-tale, indicating want of drainage.
‘Plaster-casts are made by pouring plaster of Paris, mixed to a creamy
consistence with water, into a mould made of many pieces, which pieces
are again held together in an outer or “case-mould” of two or three
pieces. When the mould is removed piece by piece, fine ridges stand up
on the cast where the plaster has flowed between these pieces. These
ridges are removed by rubbing them obliquely with the surface of the
stem of the dried equisetum. It cuts away the plaster as rapidly as a
file, but without leaving any visible file-marks. The surface left is
much smoother than from fine emery or glass-paper, and the rush does
not clog nearly so fast as the paper.
‘In order to find the explanation of this, I carefully burned some
small pieces of the equisetum stem, mounted the unbroken ash on
microscope slides with Canada balsam, and examined its structure. This
displayed a flinty cuticle, a scale-armour made up of plates of silica,
each plate interlocking with its neighbours by means of beautifully
regular angular teeth, forming myriads of microscopic saw-blades, which
become loosened from each other and crumpled up in drying, and thus
present their teeth obliquely to the surface. These teeth supply the
image-maker with a file of exquisite fineness, and harder than the
best Sheffield steel. Their comparative freedom from clogging I think
must be due to their loose aggregation while held by the dried and
shrivelled woody tissue of the sub-cuticle.
‘This natural file is used for other purposes, such as the polishing of
ivory, hard woods, and metal, but is only understood in certain obscure
industrial corners. I here commend it to the attention of my readers,
because I have just discovered a new use for it. Like many others,
I have been occasionally troubled by minute irregularities of the
teeth, lacerating the tongue, and producing small ulcerations, which,
I am told, are dangerous to those who have passed middle age, being
provocative of cancer. A friendly dentist has ground down the offending
projections with his emery-wheel, and thus supplied relief. But in
course of time other sharp angles have stood forth, but so trivial that
I felt ashamed of visiting the torture-chamber for their removal. I
tried emery paper; but it was ineffectual and unpleasant, as the emery
rubbed off. Then I tried the Dutch rush, rubbing its surface crosswise
and obliquely against the offending angles. The success was complete,
both grinding down and smoothing being effected by one and the same
operation.’