104 
RERAMIC STUDIO 
Clays give white, yellow, orange, red, reddish brown and 
violet. These variations of tone are due mainly to the differ- 
ent proportions of alumina, iron oxide and lime. Alumina 
gives a lighter tone to iron, a tone called capucine red. Lime 
determines tones varying from orange red to yellow. Certain 
ferruginous clays give a violet tone due to a special oxidation 
of the iron. 
Ochres giving a violet tone are quite common, but they 
produce mainly beautiful reddish browns. 
Manganese oxides which are commonly found in nature in 
the form of pyrolusite and acerdese, are mixed with white clays 
to give light greys and with ferruginous clays or ochres to 
give tones varying from dark grey to black. 
Manganese oxides are used as they are, but clays and 
ochres must be washed to remove the coarsest parts. This 
washing is of course done by decantation ; only the finest parti- 
cles which are in suspension are kept, and when deposited 
and dried out, they are ground either by themselves, or with 
whatever ingredients must be added to them to constitute a 
certain color. 
These colors, which, with very few exceptions, are clayey, 
must be applied on raw and in an extremely thin coat. They 
must be applied perfectly even. No better examples can be 
given than the painted potteries from Peru, Bolivia and Mexico, 
from the period preceding the conquest, numerous specimens of 
which are found in all Museums of Archeology and Ethno- 
graphy. 
As I have said before, artists will find in these old ceramics 
inexhaustible materials for decorative technique, and I am 
pleased to speak of this here because I understand that the 
teaching of ceramics in the United States includes the study of 
some processes of shape making which were practiced in the 
old time.* American teachers, better inspired in this than 
those of Europe, have realized the importance of initiating a 
student into the evolution of technical processes since the 
early times. 
I then hope that this modest contribution to the study of 
the primitive decorative technique, will be well received. 
*Biiilt pottery. 
BREAKFAST SET— ALBERT W. HECKMAN 
