Biocide for limestone

Could anyone advise on the most appropriate biocide for the
treatment of a number of archaeological architectural stone
fragments which are on display in an outdoor environment and are
suffering badly from green algae.

The stone fragments have been previously cleaned with water, gap
filled with lime mortar and consolidated with a protective shelter
coat composed of lime putty/water/skimmed milk. They are touched
regularly as they are on display within a sensory garden designed
for visually impaired people.

Any experience with this problem, such as biocide health and safety
considerations or comments about the suitability of combining
biocides with a lime based shelter coat are welcome.

Leesa Vere-Stevens
Assistant Conservator
York Archaeological Trust
Galmanhoe Lane
York
United Kingdom


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                  Conservation DistList Instance 16:36
               Distributed: Wednesday, November 27, 2002
                       Message Id: cdl-16-36-011
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