150 
The use of linseed oil, varnish, paraffin wax, and other disfiguring 
substances is not to be recommended. The fact that many of them acidify 
after the lapse of a little time makes their use actually dangerous to the 
specimen. Objects that have been treated in any of these ways in the 
past should be re-cleaned and treated properly. 
Another method of removing rust, which may be preferable in some 
cases, is to wrap strips of zinc round the specimen instead of burying it in 
granulated zinc. When wrapped in the zinc strips it is immersed in a 10 
per cent solution of caustic soda and treated as already indicated. 
Lead 
Lead is found chiefly as an inlay in tobacco pipes and sometimes as 
a sinker on fishing tackle from the Arctic. It seldom needs any treatment, 
but corrosion and tarnish do occasionally appear. They may usually be 
removed mechanically. The fact that lead is generally used in conjunction 
with stone and other materials prohibits boiling it in a 10 per cent solution 
of acetic acid in water, which is effective for specimens that are com- 
posed of lead throughout. If a lead inlay shows signs of becoming loose 
it is sometimes possible to lift it right out of the cavity, boil it in the acetic 
acid, and replace it, but such methods are not recommended as routine 
practice. A coat of the celluloid solution will prevent any further cor- 
rosion. 
Pictographs 
Pictographs are usually executed on rock surfaces in red ochre or, less 
frequently, cinnabar. They deteriorate gradually, for the washing aw T ay 
of the pigments by rain, though slow r , is continuous. Lichens also fre- 
quently grow over the pictographs and obscure them. Any attempt to 
remove the lichens while they are dry is apt to pull off the pigment at the 
same time, but it will be found that a w T eak solution of ammonia or carbolic 
acid in water will soften them so much that they can easily be removed 
with a brush. When the area has been thoroughly cleaned of dirt and 
lichens the whole surface may be sprayed with a thin solution of celluloid 
in acetone. This work should be done only when the rock is thoroughly dry, 
usually after several days of hot summer weather. This will have the 
effect of binding the remaining pigment to the rock surface and will also 
prevent the rain from soaking into the rock and freezing in winter, one of 
the most active agencies in the disintegration of rock surfaces. An area 
extending several feet away from the actual pictograph should be sprayed. 
Chemical preservatives dissolved in water will leach out in wet weather and 
are usually of little value. 
Pottery 
Pottery specimens are very common in Canadian anthropological 
collections and frequently have to be handled in considerable quantities. 
It is a mistake to put pottery away in storage without treatment, as is so 
frequently done. The specimens have, as a rule, been secured by excava- 
tion and may contain salts which will deliquesce in wet weather and 
recrystallize in dry, causing efflorescence and sometimes flaking of the sur- 
face of the pottery, a mechanical action due to the expansion of the crystals. 
Continued soaking in water is the only cure, provided that the pottery 
will permit it. This may take several w T eeks and numerous changes of water. 
