88 
FLORIDA GEOLOGICAL SURVEY-I5TH ANNUAL REPORT 
firing may prevent the concentration of the salts on the surface of the 
brick or using a reducing flame in the kiln may counteract the ill effects 
at times. Coating the ware with some organic substance such as rubber, 
tar, or flour is often satisfactory. Washing the clay in much the same 
manner as is followed in the sedimentary kaolin mines in Lake and Put¬ 
nam Counties will usually accomplish the desired result, but this method 
is somewhat expensive except for high-grade wares. Probably one of 
the most satisfactory methods of prevention is to convert the soluble 
salts into insoluble compounds. This can be accomplished by reactions 
with barium compounds. For example, if a clay containing calcium 
sulphate is treated with barium chloride the insoluble barium sulphate 
and calcium chloride results. The calcium chloride is decomposed in 
burning without harmful results. There are several ways in which this 
general method can be applied. 
