158 
Silver that needs brightening only, rather than the removal of a 
tarnish or corrosion, may be cleaned with a weak ammonia solution in 
very hot water, using a soft brush and then polishing with a chamois skin. 
Stone 
Porous stone specimens may be treated as pottery (q.v.), if they are 
found to be impregnated with salts or show signs of flaking or scaling. 
Care should be taken not to use an iron tank or vessel to soak the stone 
in as iron stains would result. A lead-lined tank is more satisfactory and 
the specimen should be kept off the bottom of the tank by small brick 
supports. Thorough soaking of stone may take several weeks or months 
and it is advisable to add a very small percentage of copper sulphate to 
the water to prevent the growth of freshwater algae. Keeping the tank 
covered and away from the light is recommended for the same purpose. 
Stones that have been painted cannot be treated in this way and it 
is generally best to apply the celluloid solution to them without any pre- 
paratory treatment. 
Repairs on stone specimens, if small, may be done with celluloid 
cement; larger repairs can be done with plaster of Paris, tinted, and, if 
necessary, tooled to produce the desired appearance. 
BIBLIOGRAPHY 
"Cleaning and Restoration of Museum Exhibits"; Third Report upon Investigations 
Conducted at the British Museum, London, H. M. Stationery Office, 1926. 
Gibson, Arthur, and Twinn, C. R.: “Household Insects and their Control"; Department 
of Agriculture, Ottawa, Bull. 112, New Ser. (1929). 
Hopkins, Albert A.: "Scientific American Cyclopedia of Formulas"; Munn, and Co. (New 
York, 1910). 
Lucas, Alfred: "Antiques, Their Restoration and Preservation”; Edward Arnold and Co,, 
(London, 1924). 
Rathgen, Friedrich: “Preservation of Antiquities"; Cambridge University Press, 1905. 
Smith, Ralph Clifton: "Bibliography of Museums and Museum Work"; American Asso- 
ciation of Museums (Washington, D.C., 1928). 
