I50 
liEKAMIC STUDIO 
would be 111 a studio kilii. The second point is the quality of 
the burn. Firing is a complex chemical process. The pro- 
ducts of combustion passing through the firing chamber exert 
important influences upon the constituents of both bodj^ and 
glaze, and successful results depend upon the control of these 
influences. 
For a quick burn glaze No. lo is the more suitable, for a 
slow bum, glaze No. Ti. In the use of matt glazes too much 
care cannot be taken to have a thick even coating of glaze. 
More trouble and dissatisfaction is caused by thin glaze than 
by anything else. In the mixing of the glaze it is not necessary 
to grind the materials, White lead and whiting are quite fine 
in their usual form. Clay or kaolin only needs to be freely 
mixed with water, and feldspar and flint can be bought ground 
from the dealers in potters' supplies or from wdrolesale chemists 
such as the Roessler & Hasslacher Company, loo William 
Street, New York. 
The mixture being weighed out the whole batch should 
be triturated in a mortar and passed through a sieve of 20 
meshes to the inch. Water is added until a thin paste is sec- 
ured free from lumps. The batch is now placed in a deep bowl 
and thoroughly mixed with a Dover egg beater or else is put 
into a "Christy improved mixer" (The Christy Knife Co., 
Fremont, Ohio) and worked until smooth. A mucilage must 
be supplied in order that the glaze may not crack while drying. 
The best mucilage is made from gum Tragacanth. A small 
handful of the gum, not powdered (about i oz.) is put into two 
quarts of cold water and steeped for 24 hours. At the end of 
that time the mass must be well worked with the egg beater or 
in the Christy mixer until free from lumps. More water is 
added if too thick but it is best to have a good thick gum. A 
few drops of carbolic acid or some other convenient germicide 
will prevent any offensive odor from developing. Taking the 
glaze from the mixer it should be set in a deep narrow jar, such 
as a Mason fruit jar, and allowed to stand and settle. All the 
clear water is then poured off and a tablespoonful of mucilage 
added to every 1 00 grammes of dry glaze in the mixture. Glaze 
so prepared can be kept indefinitely in an air-tight jar and will 
always be ready for use. 
To glaze the pottery the whole batch of glaze should be 
emptied into a bowl and well stirred. The pottery is thoroughly 
saturated with clean water to prevent absorption and conse- 
quent irregularity and must be wiped dry from all surface 
moisture. The glaze, which should be as thick as a rich 
mayonnaise, is poured evenly over the ware which is then set 
aside to dry. 
In preparing the piece for the lain the bottom of each is 
sponged clean as to the edge, but the appearance of the under 
side will be improved if the glaze is left in the center. A 
connoisseur in pottery instinctively looks at the bottom of a 
piece and the clever worker wdll endeavor to have the bottom 
as well finished as any other part. There is an objection to the 
use of stilts in the kiln in that the three point marks are always 
in evidence. A better plan is to make circular supports out of 
a mixture of kaolin and flint. The size of these can be adjusted 
to each vase made and should be arranged so that the clean rim 
beneath the vase rests on a raised edge upon the supporting 
bat. The clay and flint mixture is so infusible that even if it 
adheres to the glaze it can easily be rubbed off with a piece of 
hard stone or a carborundum knife sharpener. 
For coloring these glazes the usual metallic oxides, oxides 
of copper, cobalt, iron and nickel can be used. Cobalt oxide 
needs to be verj^ finely ground for the strength of color is so 
great that even a small grain wifl produce a dark speck. If it be 
quite impossilDle to manage this the best plan is to use, not the 
oxide but the nitrate of cobalt. This is soluble in water 
making a clear crimson liquid. A few drops of the solution 
put into the glaze mixture will produce the same effect as the 
oxide without the disadvantage of blue specks. The only ob- 
jection is that the nitrate is rather more expensive. How- 
ever, so small is the quantity necessary that the cost is scarcely 
noticed. The remaining oxides, copper, iron and nickel may 
be added to the glaze mixture and stirred in with the egg beater. 
For a light color the total amount of stain should not exceed 
one per cent, while three times this quantity is enough to pro- 
duce a rich tone of color. 
It may be well to add, for the information of any who 
have not read previous articles that copper produces green, 
to be modified in the direction of blue by cobalt and in the 
direction of yellow by iron; that nickel produces gray which 
can be modified in the same manner and that cobalt can always 
be relied upon for blue. Red is hard to secure but can be made 
wdth iron if the glaze is laid on in a thinnish coat over a Hght 
colored clay. Of course if a red clay be used for the pottery 
it may be left unglazed for the sake of the color. 
1 Smithsonian M 
Vase of White Chienlung Porcela; 
INDIAN GRASS 
Kathryn E. Cherry 
FIRST Fire: — Use Yellow and Blood Red pale for flowers; 
for shadow flowers use Blood Red and Violet. Leaves 
made of Moss Green, Brown Green, Shading Green and Black'. 
Second Fire: — Use Rose in high lights. Blood Red and 
Violet. Stems are Yellow Browai, Blood Red and darkest 
touches of Auburn Brown. Background, Violet, Yellow, Sea 
Green and Copenhagen Blue. 
