Causes And Disadvantages Of Alabaster

Abstract

Alabaster is an ornamental stone that was widely used in ancient Egypt and it had a lot of deterioration factors. The present paper deals with two types of alabaster that located at Wadi

Sannur and Wadi El Assuity, and their durability and geotechnical characteristics. These characteristics were examined before and after artificial ageing using simple analytical methods.

Physical and mechanical properties were carried out on samples from quarries providing each type and the same samples were then exposed to artificial ageing with sodium chloride and heat which effectively produced deterioration comparable with that in Luxor and Karnak temples. The results were tested on different alabaster objects from Luxor and Karnak temples

where

(6-a, b, c).

Microcracks as a result of mechanical stresses which may originate from mechanical loads, from of variation in temperature and humidity, from aggressive environment which can be acid residue from rainfall and product from a calcite reaction [15]. Alabaster decay represented characteristic in numerous pitting and cavities, fig. (7-a, b, c).

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Figure 4 (a, b, c) Alabaster monuments at Karnak temple showing the effects of bleaching by sunlight A B C

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Figure 5 (a,b,c) the Granular disintegration on the surface of alabaster offering table at Karnak temples and fracture and loss some architectural elements of alabaster monuments at Luxor.

Figure 6 (a, b, c) the cracks and microcracks and fissuring at the alabaster monuments at Luxor and

Karnak temples.

Figure 7 (a, b, c) the different pitting and cavities in the alabaster monuments at Luxor and Karnak temples. The reasons of this deformation are the rainwater, which is always slightly, because air contents carbon dioxide that is dissolved in water forming carbonic acid.

Under such condition, carbonates of calcium may be transformed

Most spectacular examples for proceeded weathering are completely destroyed offering table at Karnak temple.

The final stage of this weathering is frequently characterized by disintegration of the alabaster; the cohesion between the grains is completely lost. The reasons of the observed deformation dramatically for repeated heating may lead to permanent dilatations due to microfracturing.

Variation in moisture contents may be responsible for the deformation. Water is one of the main factors of decay of alabaster stone which one of the porous stone at Karnak and Luxor temples, as it plays a crucial role in almost every decay process, water penetrate into the pores of the stone by many ways as capillary suction from the soil or by condensation from the atmosphere. Thus water carries into the stone soluble salts which can crystallize in correspondence of the evaporation surface owing to the solution supersaturation. This process is the main cause of the efflorescence and subefflorescence formation. Halite and gypsum are the common salts at the alabaster stone in Upper Egypt. Halite and

Gypsum are hygroscopic salt