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The Danger of Salt and Water Infiltration |
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The same area with new damage in 2000. New damage in 2001where pieces have broken off. |
The destruction takes a number of forms. Dark brown patches show where the salt laden stone absorbs moisture like a sponge. Areas of crystallized salt resembling frost appear on the walls where salt laden moisture has evaporated. In some places, the decoration is covered by a thick, blistered crust of salt and dissolved sandstone as hard as concrete. Here the reliefs look as though they have partially melted. Worst of all are powdery blotches of sulphurous yellow, where the salts have severed the chemical bonds holding the stone together, and it has reverted back to the sand from which it was made. It then crumbles like a dried-out sand castle. |
