By Abeer F. Elhagrassy and Amira Hakeem

The present research showed two types of cleaning methodology based on: a) biological self-cleaning
technique, and, b) laser technique, were used to clean the weathered stones from black encrustation layers.
This paper aim was to compare the efficacy of using biotechnology and lase methodology for cleaning the
deteriorated surface layer of the limestone by sulphation which is called black crust. Nd: YAG laser and a
Sulfate-reducing bacteria Desulfovibrio desulfuricans were carried out on fragments stone from three columns
in Failaka Island in Kuwait.
Both two techniques succeeded in removing the black encrustation, the laser procedure was fast and well
controlled, but it doesn’t save the noble patina of the stone. The biological technology was risk-free, highquality
performance, simple to apply, cost effective, and it protects the noble patina of the surface stone.


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