RERAMIC STUDIO 
149 
the fingers so as to avoid clods, until the water is completely 
covered with it. Then it is beaten and left to catch. It be- 
comes firm, hard and possesses onh^ what porosity this matter 
alwaj's has. It is the ordinary preparation of plaster and suit- 
able for pressing moulds. 
But in casting, as the moulds must absorb promptly the 
water of the slip, they must be extremely porous. This excess 
of porositj'^ is obtained by making thin. The operation is easy, 
but requires care and a little practice, as on the success of the 
mould depends that of the vase. The water is placed in a basin 
and the plaster sprink'led with the fingers as before. But this 
time the water should not be entirely covered with plaster. 
Before it begins to work, at the very time when it is going to 
catch, it is beaten and thoroughlj' diluted, then left to rest a 
few seconds, after which time a quarter of water is added, that 
is, a quantity equal to the quarter of the quantity used for the 
first mixture. It is well to measure this water. The object of 
this additional water is to delaj' the coagulation of the plaster, 
to prevent its hardening. Besides, lodging itself in the pla,ster, 
the water occupies room which after evaporation constitutes 
large and numerous pores. When ready to coagulate, the 
plaster is stirred again. It becomes then thick and past^^ It 
is in that condition that it must be used, but one must hurry 
up in making the mould or part of mould one is working on. 
Casting moulds are distinguished from pressing moulds bj^ 
the generalty vertical sections (fig. 20) and by no necessitj^ for 
the chape which holds the parts. For this reason thej^ are less 
complex and less expensive. To be sure that the different 
parts of a mould will join weU and will not move, grooves R 
are made with a gouge, outside, on top and bottom, if the mould 
is more than 6 inches high, in the middle only if it is smaller. 
In these grooves are solidlj^ tied strong pieces of twine. 
When a casting mould has been used many times, the 
seams on the cast piece have a tendency to appear rather large. 
To avoid tlris, moulds with split pieces can be made (figs. 15, 
22 and 23) . In this case the mould maker divides the mould in 
one or two blocks on which he makes with a saw a large furrow 
S, being about 4-5 of the total thickness. In this furrow he 
places the edge of a cold chisel and gives it a sharp blow with a 
hammer. The part A which has not been sawed is split and its 
section is capillary. However, moulds with this angular section 
require more attention in the manipulation of pieces. 
All casting moulds have a false rim. This is an extension 
of the top of the piece to be made (figs. 13 and 24) . The part of 
the mould where this false rim A is, holds the slip, the level of 
which varies with the successive opening and closing of the 
suppljmig faucet, while the top of the vase will receive a uniform 
supply of slip and will have the same thickness as the other 
parts. The false rim in a cast vase must be removed only 
when the latter is thoroughly dry. It is taken off, either by 
hand with a very sharp blade, or on the wheel with a .stroke of 
the turning tool. 
'• Ceramic utensils must be entirely in zinc with tin solderings 
and if necessarj^ copper rivets. Any particle of iron must be 
carefully avoided. If iron is not injurious to gr^s, it is most 
dangerous with porcelain. The plumbing must be in lead. If 
oxide of zinc and oxide of lead are formed they have no injur- 
ious action on porcelain. 
These utensils must always be thoroughly' washed after 
each operation, especially when two materials as different as 
gres and porcelain are used. In their inside construction all 
^^•^(S 
angles, which are difficidt to clean, should be avoided. So the 
pails instead of having a convex bottom like A in fig. 25 should 
have a concave one like B in fig. 26. 
All tools and apparatus described in this article are those 
which I use every day. They are of my own design but have 
been constructed by Mr. Poyard, engineer, 48 rue des Cendriers, 
Paris. 
The lead pipes must have no right angle, they must be 
everywhere of the same diameter, perfectly smooth, curved if 
necessary, but without any angles or asperities which would 
prevent the slip from flowing freely. 
None of the details which I have mentioned must be neg- 
lected. They are the result of gradual improvements during 
a long practice of casting. By following them literally, begin- 
ners will avoid a good deal of trouble, expense and disappoint- 
ment. 
I will not speak of the casting of large pieces, the description 
of which would fill two long articles and would go beyond the 
object of this writing. I will simply say, as a matter of interest, 
that for large vases it is necessar}' to make a vacuum with an 
air-pump. 
In conclusion I will advise the adoption of the paste PN 
Frugier for the porcelain pieces pressed and turned, and the 
special paste for casting PN for cast pieces. The same glaze 
will fit both. The fusibility of the cast pieces being somewhat 
greater they should not be placed on top of the kiln. 
For cast pieces of large or medium proportions the ordi- 
nary paste PN can be used advantageously,the special paste 
being mostly useful for small pieces and fancy shapes which are 
not easy to take out of the moulds. 
The first pieces obtained with this casting process will be 
the most powerful stimulus for the operator. 
SCHOOL NOTE 
' The School of Decorative and Applied Art, of New York 
City, is sending out a number of leaflets bearing on the course of 
study to be pursued this winter. Here as everywhere the 
arts and crafts influence is strongly felt and the winter's work 
win doubtless show a decided advance along these lines. 
