| Its marble appearance, its ductility
and translucence make alabaster a worthy material from ancient
times because of its ornamental values. The name of this mineral
comes from Alabastra, a city of the Ancient Egypt where it
was dug out. Egyptians, Greeks, Etruscans and Romans made
use of it for architectural coverings and for sculpting vases
and statues. The Paleochristian, Byzantine and Romanic architecture
used it instead of glass for covering windows and it has been
employed through the centuries for sculptures in Spain, Italy,
England and Germany. Presently it is used in sculptures, in
ornamental pieces and in buildings.
The Mercedes Artal, Alabastro de Sástago enterprise
covers requests by means of planes and designs for alabaster
panes on windows and on rose windows; panelling of walls
and ceilings, enclosing walls which filter the light; columns,
corbels, mouldings and other applications for ornamentation
and lighting, for example, wall lamps, lamps, etc.
Applications of Alabaster
Architecture: Big panes of alabaster
for panelling, covering walls and enclosing walls which
filter light warmly.
Restoration: The Alabastro de Sástago
craft workshop has collaborated with architects and restores
to recover Aragoneses buildings of such a quality as the
palace of Armijo (nowadays the site of the Justice of Aragón)
or the Saint Nicholas church in Zaragoza; the cathedral
of Jaca, the cathedral of Albarracín, the monastery
of Veruela, the Monastery of Stone, the monastery of Rueda,
etc.
Decoration: Ornamental objects of all kinds.
Vases imitating Egyptian, Greek and Roman vessels, and works
of contemporary style as well.
Lightning:Thanks to light, alabaster shows
its true expressive qualities. Nothing is so noble as natural
stone with veins and colours to give light warmness to very
different atmospheres. From large spaces –by means
of large panes and big pieces–, to family houses,
wall lamps or lamps with a lampshade stuck on the ceiling,
combined with forge works, wood and other noble materials.
Technical features of alabaster
from Aragón*
Mineral: variety of competent, massive
gypsum which has crystalized and is translucent with light
colours.
Beds: underhorizontal levels of blocks
with maximum dimensions which oscillate from some centimetres
to two metres.
Compositionn: two water molecules hydrated
with calcium sulphate (SO4Ca+2H2O); approximate proportions:
SO2 = 43%; CaO = 35%, and H2O = 22%.
· Coefficient of water absorption: to 60ºC
= 0%; to 110ºC = 5.2%.
· Hardness in Mohs: 47 kg/mm.
· Porosity: 0.15%
· Specific gravity: 2.4 gr/cm³
Average index of resistance to freezing:
drying to 40ºC = 0.94%
drying to 60ºC = 0.68%.
Resistance to thermic changes:
To 40ºC = 2.8% of weight variation
and 68.4 kg/cm² of resistance to flexion
To 60ºC = 3.0% of weight variation
and 8.8 kg/cm² of resistance to flexion.
Resistance to compression:
200 kg/cm²; under a freezing test
to 60 ºC it may reduce a 35% its resistance.
Module of elasticity: 32 Kg/cm².
Resistance to flexion: 82kg/cm²
Resistance to acids: 0.6% of weight variation
and loss of resistance at 20% of flexion.
Resistance to shocks: 38.3 cm.
Performance with light: opacity at 110ºC.
Análisis y ensayos realizados
por Laboratorio de Ensayos Técnicos, S.A. (ENTECSA)
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