Sepiolite is a white clay mineral composed
of hydrated magnesium silicate and used to remove ingrained dirt from
marble. A poultice is made by mixing de-ionized water and Sepiolite
and is applied to the surface by hand to a thickness of 20mm. After twenty-
four hours, slight cracks will appear in the partially- dry poultice; it
should then be removed a little at a time and the moist, freshly exposed
surface immediately washed with distilled water, sponges, and brushes.