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For old, worn, scratched, stained slabs, etc., it is recommended
that a general rubbing down shall be done with water. This
will abrade the surface layer (1 to 2 mm), restore the natural
appearance to the slab and make it perfectly plane without
any level difference between tiles. The operation is done
using a floor grinding machine fitted with a tray supporting
abrasive wheels or a diamond disk. Successive passes are made
with increasingly fine abrasives until the required appearance
is obtained: from rough grinding, mat smooth, satin finish,
to polish (special wheels).
Joints, holes, hollow veins, stylolites, must be carefully
filled with mastic and appropriate binders during the final
passes.
 Crystallization
For the hardest stones (marble, marbled stone), it
is also possible to achieve a gloss polished appearance by
crystallization. Its theoretical principle is based on a chemical
reaction of calcium carbonate with a solution of magnesium
fluorosilicate and phosphoric acid in the presence of a catalyst
(iron). This reaction transforms the surface calcium carbonate
into calcium fluoride and magnesium fluoride crystals for
a depth of a few tens of millimeters.
Crystallization must be done on a slab in good condition
with no scratches, and different steps must be respected:
- stripping-abrasive cleaning with a single brush, possibly
with the addition of stripping products, to remove in depth
dirt and cleaning products embedded in the stone. Rinse and
allow to dry.
- crystallization is then done by spreading the crystallizing
solution on the floor (without excess) and spreading it with
the single brush crystallizing machine fitted with a disk
made of fine steel wool. Forward-return passes are made without
remaining in the same place for too long, until the required
gloss is obtained.
- A final lustring with a very soft disk improves the gloss
if necessary.
The gloss needs to be redone at variable frequencies depending
on the intensity of traffic and the nature of the stone. This
operation is done in exactly the same way as the first crystallization,
but without prior abrasive cleaning or rubbing down steps.
Crystallization is efficient for a period of 6 to 12 months
for moderate public traffic.
IMPORTANT : This renovation
and restoration work requires good knowledge of the nature
of the stone, materials to be used and products to be applied
and must be done by a professional.
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