Mineral ground is a
preparation of varnish and a mineral which seals the wood prior to
colored varnish being applied. It serves in various ways to enhance the
sound, protect the wood and contribute to a beautiful, transparent look
to the finish. This is something you see on classic instruments. Many
studies have demonstrated that some combination of a durable mineral
(i.e. pumice, mica or silica) was applied at an early stage in
varnishing. While
you can buy pre-ground minerals from various sources, grinding your own
guarantees a consistent color and the correct consistency.
The preferred mineral I use is pumice. I have found Italian pumice stone to be the clearest in color.
To prepare your own pumice powder: Begin with a whole stone of pumice. Using a small hammer and a mortar, gently break up the rock into pea-sized pieces. Next, use the pestle to break the pumice into small granules. Transfer the pumice to a glass plate and grind it into a fine powder using either a muller or a second, smaller glass plate.
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