RERAMIC STUDIO 
CLAY IN THE STUDIO 
(Twelfth Paper.) 
Charles F . Binns 
O doubt anxious and progressive 
artist potters have been looking 
forward to instructions for prepar- 
ing the coveted "matt" glazes and 
the time seems now to have arrived 
when these vany be given. A -word 
of caution must, however, be spoken 
at the outset, for those who have 
successfidly produced bright glazes 
must not expect the same easv 
victory over tne matt. Let not this be understood to mean 
that bright glazes are necessaril3^ easj^ A simple bright glaze, 
of a sort, presents no difficulty, but in order to produce really 
fine and brilliant glazes, free from the long catalogue of defects 
spoken of in the last paper, much knowledge and perseverance 
are necessarj^. No glaze making can, as a matter of fact, be 
perfect without assiduous application and considerable scientific 
knowledge. As stated two months ago that knowledge will not 
be presumed in these instructions. It is thought best to place 
the matter on such a footing that even the beginner can hope 
for success, but it must be repeated that failure to reach one's 
ideal must not discourage, there are very few even among ex- 
perienced and scientific workers who realize all they want. 
Matt glazes are so constructed that the svirface, on burn- 
ing, assumes a tender, silky texture, not dead like biscuit 
ware, nor scummj^ like half-burned glaze, but of a quality like 
the shell of a duck egg. This texture is a matter of the chemi- 
cal constitution of the glaze but it is largely influenced iDy many 
secondary considerations. Matt glazes as compared with 
bright are harder to prepare, harder to appty and harder to 
bum. 
Presuming the heat of the kiln to be cone i , or a little 
more, a matt glaze can be made from the following mixture : 
White lead 35 
Whiting 10 
Feldspar 37 
Zinc oxide 3 
Kaolin 13 
Flint 2 
The materials are to be weighed out and blended as de- 
scribed for bright glazes and the ware may be prepared for 
dipping. To secure the best results matt glazes must be laid 
on in a very thick coat but if enough glaze cannot be got to 
adhere the first time the piece should be burned and re-dipped. 
An attempt to add a second coat when the first is only dried 
will surely end in disaster. The glaze must be used very thick, 
so thick that it will only flow sluggishly from the hands. It is 
an advantage to mix some mucilage with the glaze, starch paste 
or dextrine or gum wiU answer, the object being two fold 
(l) to secure an even flow and (2) to enable one to handle the 
piece when dry. 
The pottery to be dipped must be rendered non-absorbent 
by soaking and be thoroughly dried oft'. The inside of the 
piece is first fiUed and well shaken out and then the attention 
can be devoted to the outer surface. Everything should be 
placed in readiness for drying the ware for no touch can be 
aUowed after dipping until quite dry. A thick coating is 
poured on with the hand and the piece shaken lightly with a 
circular motion so as to distribute the glaze evenly without 
losing uuicli. 
The beginner's mind must be made up to endure disap- 
pointments. Time and time again it will be found that the 
dipping has been unsuccessful. The glaze is streaky or lumpy 
or has gathered more thickh^ here than there. Fortunately, 
however, these troubles can usually be detected before burning. 
If so it is better and cheaper to wash the glaze off and laegin 
again. The material need not be lost. If washed into a clean 
basin it will settle clown and can be collected and returned to 
the batch. It must be remembered that the fire has but little 
power over matt glazes and the glazes themselves little mobil- 
it^^ In bright glazes a scratch or a patch is of small import- 
ance, the glaze will flow and heal the defects. Not so in the 
matt. As this goes to the kiln sojt will come forth. Every 
finger mark, every inequality will remain. and will show up in 
all its crudity, many more, in fact, than were suspected. 
The burning of the glaze will surely reveal errors which were 
before unseen. The remedy is practice, practice and yet again 
practice! 
Grudge not the glaze material. Wash oft" and redip again 
and again if necessary, not resting satisfied until a smooth even 
coating can be secured and the fingers removed without leav- 
ing a mark. 
One of the chief troubles arising in the glaze is that it is 
prone to crack in drying. The thicker the body of glaze the 
worse this is apt to be. There are several remedies, some- 
times one will suffice, sometimes m^ore than one must be tried. 
An increase of mucilage will prove helpful but renders the glaze 
bad to keep. In fact in all mixtures with mucilage it is best to 
add a few drops of carbolic acid or some other germicide. 
This will keep the glaze sweet. Another remedy is to bum the 
kaolin before adding it to the glaze. This is not easy in the 
absence of a mill, for the particles of clay become hard on burn- 
ing and need to be grotmd. The trouble may, however, be 
overcome bj^ reducing the kaolin to a very fine powder before 
liurning it. If this is done and the substance sifted through 
a fine sieve it can be carefully placed in a biscuit cup or crucible 
without being packed down and it will retain its fine grain in 
the burning. It can then be easily crushed in a mortar by 
hand. If the glaze is inclined to dust off on the fingers it may 
be well to use ball-clay instead of kaolin. This clay has greater 
binding power and will help to hold the glaze together. vStill 
another expedient is the addition of a little soluble salt, washing 
soda or saltpeter, to the glaze. A pinch is enough, it will not 
hurt the glaze but will aid in binding it. 
The faults arising in matt glazes are somewhat different 
from those found in bright glazes. Crazing does not seriously 
trouble because it is scarcely visible when it occurs and, the 
pieces being mostly ornamental in character, does not amount 
to a hygienic defect. Shivering, on the other hand, is common 
upon some clays. The body given in these papers does not 
shiver with these glazes but many natural claj'-s will do so. If 
the glaze be laid thickly on a thick piece of ware the fault 
shows in the pulling out of pieces from the edge or along any 
embossed portion. On thin ware the result is the fracture^ 
often with almost explosive force, of the entire piece. No 
remedy is possible except to change the clay. 
It is sometimes found that the surface of a matt glaze wiU 
be fiUed with smafl holes, even approaching to a spongy ap- 
pearance. This is due either to a lack of heat in the kiln or to 
the fire not being kept clear. Any approach to a "reducing" 
flame will cause this phenomena and the remedy is, of course, 
to be sure that the fire be completely oxydising. 
The composition of a matt glaze has a great influence,not 
only upon the point of fire at which the glaze assumes its per- 
fect texture, commonly called the point of matin-it\'. iMit upon 
