Marble And Granite - What Produces The Shine?
Many people make the assumption that marble, granite and otherfinely
polished natural stones shine because a 'polish' has beenadded to them.
Nothing could be further from the truth.
Natural stones are made of crystals. The crystals are made up
ofdifferent minerals. Each mineral forms a different crystalshape. These
different crystals interlock together to make upthe stone. When stone
is first quarried it has a very roughtexture to its surface as it breaks
along the crystal joints. Byusing a series of graduated grinders the
stone is ground down.The grinders are normally made from industrial
diamonds and tostart the process a very rough one is used. It is the
sameprinciple as sanding down wood. You start with glass paper thatis
very coarse and gradually use finer and finer glass paperuntil you have
a fine, smooth finish to the wood. With stone theglass paper is replaced
with diamond studded pads and these getfiner and finer.
What the grinding is doing is cutting the rough edges off thestone
by scratching it and as the diamonds become smaller andsmaller the scratches
become finer and ultimately microscopic.What you end up with is a very
smooth surface to the stone. Thecrystals have by a slow process of finer
and finer grinding beenworn down until on the surface they are all perfectly
flat andsmooth with each other. A perfectly flat surface will reflectthe
light uniformly and will look
like glass.
Consider a mirror that reflects light uniformly giving you aclear
sharp image. Make the glass curved or rippled and you geta less clear,
less sharp image reflected back. The same appliesto stone. If the crystals
are flat then you get a perfect imagereflected back and the stone looks
incredibly shiny. Roughen thesurface slightly and the reflected light
ceases to give you aperfect reflection and the stone begins to dull.
Anyinterference with the stones surface can cause this dulling toappear.
It could be a series of minute scratches made by dirt orit could be
caused by acid materials etching into the stonedestroying its shine
in that region.
To get the shine back the stone must be ground down again.Consequently
the shine on a stone is not the product of addingsome chemical to the
stone but is a property of the stoneitself.. The harder the stone the
more difficult it is to grindbut the greater degree of shine that can
be achieved, which iswhy polished granite has the greatest degree of
shine, followedby marble then limestone.
About the author:
David Andrew Smith runs http://www.wesparkle.co.uk/ a contractcleaning
company which specialises in cleaning and polishingnatural stone as
well as providing cleaning services throughoutthe UK
