26th century BCE – 26th century BCE
Giza, Egypt
The Sphinx at Giza is identified in the passage as a limestone monument whose deteriorating neck received a chemical strengthening treatment in July 1973. The treatment used a concentrated solution of barium hydroxide with urea and glycerol, and its reported success was still considered provisional because long-term observation was required.
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The Story
The passage presents the Sphinx at Giza as a case study in the conservation of deteriorating stone monuments. Its limestone surface was exposed to the broader problems affecting African monuments, especially the effects of weathering and the progressive loss of surface material. Chemical consolidation was described as a difficult field in which earlier treatments had often proved ineffective or harmful.
Professor Lewin developed a method intended to strengthen limestone and marble surfaces by treating deteriorated areas with a hot concentrated solution of barium hydroxide, containing urea and glycerol. The chemical principle was the replacement of calcium ions in the decayed stone with barium ions. The resulting barium carbonate was intended to become part of the stone rather than form a separate surface coating liable to detach.
The treatment was applied in July 1973 to the disintegrating surface of the Sphinx’s limestone neck. The immediate result was described as satisfactory at the time of writing, but the passage stressed that at least another ten years of observation would be needed before the method could be judged valid for the long-term conservation of deteriorating limestone.
26th century BCE – 26th century BCE
Giza, Egypt
The Sphinx at Giza is identified in the passage as a limestone monument whose deteriorating neck received a chemical strengthening treatment in July 1973. The treatment used a concentrated solution of barium hydroxide with urea and glycerol, and its reported success was still considered provisional because long-term observation was required.
Continue exploring
The Story
The passage presents the Sphinx at Giza as a case study in the conservation of deteriorating stone monuments. Its limestone surface was exposed to the broader problems affecting African monuments, especially the effects of weathering and the progressive loss of surface material. Chemical consolidation was described as a difficult field in which earlier treatments had often proved ineffective or harmful.
Professor Lewin developed a method intended to strengthen limestone and marble surfaces by treating deteriorated areas with a hot concentrated solution of barium hydroxide, containing urea and glycerol. The chemical principle was the replacement of calcium ions in the decayed stone with barium ions. The resulting barium carbonate was intended to become part of the stone rather than form a separate surface coating liable to detach.
The treatment was applied in July 1973 to the disintegrating surface of the Sphinx’s limestone neck. The immediate result was described as satisfactory at the time of writing, but the passage stressed that at least another ten years of observation would be needed before the method could be judged valid for the long-term conservation of deteriorating limestone.