250 
RERAMIC STUDIO 
AMERICAN CLAYS FOR PORCELAINS AND KILN USE 
Charles F. Binns 
HE articles b}^ M. Taxile Doat now 
appearing in these pages are of the 
highest importance to every one in- 
terested in the progress of the cera- 
mic art. Coming, as they do, from 
the pen of one who has himself 
performed those things whereof he 
writes, they constitute the most im- 
portant pronouncement upon the 
production of hard porcelain which 
has appeared in the English language. An}^ one who has seen 
and handled M. Doat's dainty creations cannot but feel a glow 
of gratitude towards him for having with the utmost generosity 
laid bare his art to the brotherhood. 
It is with the view of making the work of the famous 
Frenchman more useful to his American readers that these 
lines are penned, for it is very evident that claj's and pastes 
camiot profitablj^ be imported by those who desire to take 
advantage of the information given in the articles. Nor is 
there need of this for our own land contains clays as fine as anj' 
in the world and in the school over which the writer presides 
beautiful porcelains have been made from purely native 
materials. 
Instructions for mixing and preparing bodj^ claj? have 
already been given in the articles on "Claj^ in the Studio'' and 
need not be repeated here. The procedure is the same except 
that porcelain clays contairung no ball cla37 are ver\^ short and 
must be aged and well worked to develop plasticitj^. Fortu- 
nately however, we in America are placed under a considerable 
advantage in the possession of our Florida cla5^ This clay, 
while in reality a ball clay, having been washed away from the 
site where it was formed, is virtually a kaolin with a high 
plasticity. This clay may be obtained by the barrel from the 
Golding Sons Co., Trenton, New Jersey, or East Liverpool, 
Ohio, it is called simply Florida clay. 
The following kaolins are suitable for use in porcelain 
bodies : 
Harris Kaolin, the Harris Clay Co., Dillsboro, N. C. 
Georgia China Cla^^ I. Mandle, Clay Merchant, St. Louis, 
Mo. 
Delaware Kaolin, the Golding Sons Co., Trenton, N. J., 
and East Liverpool, Ohio. 
Ground flint and feldspar may be obtained from the; 
Illinois Mineral Milling Co., East St. Louis, Illinois. 
The Golding Sons Co., or the Eureka Flint and Spar Co., 
Trenton, N, J. 
The chief difficultj^ which will be met with in these last 
named materials is that thej' are rarely found, in commerce, 
ground fine enough for use in porcelain. Hence it is impor- 
tant that the maker of porcelain should instal some kind of 
grinding machinery. 
Porcelain is an exotic in this country and the pastes cannot 
be bought readj^ prepared as they can in France, moreover, 
the making of porcelain is an art of extreme difficulty and half 
the battle is in starting right. One who is unable to under- 
take a reasonable outlay at the beginning has but .small pros- 
pect of success and it is best therefore to carefully count the cost. 
Porcelain can be made at temperatures ranging from cone 
9 upwards, cone 13 being as high as one has ever need to reach. 
The limit is not in the bodj^ composition but in the glaze. 
Translucent white wares can be made as low as cone 4 but the 
true porcelain glaze is one without lead or boracic acid and this 
cannot be produced, in the i:)resent condition of the art, below 
the temperature named. The mixture for a porcelain body to 
mature at cone 13 will be somewhat as follows: 
Harris Kaolin 25 
Georgia Kaolii:i 20 
Florida Clay 15 
Flint 25 
Feldspar . 15 
and for lower fires the feldspar must he increased and the 
kaolin lowered. 
The two kaolins are not absolute^ necessary, but better 
results are to be obtained by using both than by either one alone 
A porcelain glaze for cone 13 will he the following: 
Feldspar 25 
Whiting II 
Kaolin 19 
FUnt 45 
For lower fires the kaolin and flint should be reduced. 
Success in porcelain making depends, as will be gathered 
from M. Doat's articles, upon the proper proportion and use of 
saggers and other placing material such as rings, bats and props. 
No cheap clay will do for these, for the stress of the fire falls 
upon them and if they fail the whole of the labor will be lost. 
Many highly refractory sagger clays exist in the country, 
some of these are in use as glass pot clays and,while too expen- 
sive for factory use, may well find a place in the studio. Some 
of these clays are mined in a hard rocky form and must be 
purchased in ground condition or they will be useless. The 
following list of merchants and their products comprises all 
that will be necessary: 
The Warrenite Co., St. Louis, Mo., ground Warrenite. 
The Christy Fire Cla3^ Co., St. Louis, Mo., ground glass 
pot clay. 
W. H. Cutter, Woodbridge, N. J., sagger clay. 
I. Mandle, St. Louis, Mo., Tennessee ball clay No. I. 
The Golding Sons Co., Trenton, N. J., Florida clay. 
The Christy claj^ and Warrenite are not suitable for use 
alone, liut are most valuable in mixtures; some plastic clay is 
necessar3- to combine with them. Tennessee ball clay is the 
most plastic in the list but not refractory enough for use alone. 
Florida claj^ is both plastic and refractory but^expensive. 
An important factor in the blending of sagger clays is 
"grog." This is the name given to any burned clay which is 
crushed and added to the mixture. The object of this is two- 
fold, it helps to diminish shrinkage and thus to keep the forms 
true and it adds to the porosity of the pieces and permits the 
passage of kiln gases, thus making the fire more effectual. The 
]5reparation of grog is important. At first it must be made of 
pure calcined clay. After one or two burns the supplj' of 
broken bats and saggers is more than sufficient to supply grog. 
In making grog for a beginning, the fragments of clay 
should be reduced to the proper size before burning as the dust 
can be used in mixing and there is no waste. Two sizes will 
he needed; for saggers the grog should range from the size of 
ground coffee to that of split peas, for bats and supports from 
the size of ground coffee to that of mustard seeds. A coffee 
mill is, b\'^ the way, an excellent tool for grinding the smaller 
sizes and an adjustable mill can sometimes be set wide enougli 
for even the split pea size. Three sieves are necessary, having 
respectiveh^ eight, fourteen and twentj^ meshes to the linear 
inch. These can be made to lock together, the coarse one at 
the top, so that the whole sifting is but one operation. The 
crushed clay is placed on the coarse sieve, that which will not 
jjass is re-crushed, that which lies upon the second is used for 
saggers, and that upon the' third for bats and props. The dust 
passing through the third sieve is returned to the clay box for 
