RERAMIC STUDIO 189 
CLAY IN THE STUDIO ' ware at that heat. In selecting clays it is best, for low tem- 
(Third Paper) perature work, to choose those which become dense in the fire 
Charles F. Binns when unmixed with any other substance. Most Ball clays are 
, T T . , . . , suitable, notably the clay of the Excelsior Ball Clay Company, 
yV 4 LL clays possess two properties, plasticity and n . . Tr , ./ . , . „ . , T 
w/^miL • , , . , , Covington, Kv., and the clay of the Construction and Im- 
porosity, and when a given clay has to pass . ^ «., _ , , Tr „, , . 
f, ,,,-.,,, rt- • , provement Company, Mayfield, Kv. These clays are both 
through the fire it should, and at sufficient heat , , , .. , ' ... ' , .. . T , 
.,. f . ... , , . .- dense and plastic, but will not make a pure white ware. Much 
will, develop a third property, that of vitrinca- , .,_ , ^ . . ,. „. . , , , r . 
, r . , , ,., • whiter, but not so dense, is the Florida clay spoken of in the 
tion or becoming more or less glass-like in na- , t ~. . , , , . « r -n- ^ i ■• 
. . ,. ,, , r 1 1 last paper. 1 his mav be procured from the William Golding 
ture. A due regard for and balance of these three c >/- t« '*. -vr t /- in- , 
..... , . , . Son s Company, Trenton, N. J. Ground flint or quartz and 
properties is necessary it a clay, either natural or mixed, is to , , . . , ' , r _ ,, . ^ 
\ r , ,...', ^ , ground feldspar may also be procured from the Golding Com- 
be successfully used by the potter. For coarse wares such as , ., ^ . „,. , , „ ' „ & 
... ., J , . J ...... , r . , pany or from the Eureka Hint and Spar Company, Trenton, 
brick or tile a clay is sought which, in itself, has these proper- x , T _,, ~, , .. r ... . , J, 
.,,.,,„£ . . ., , : . N.J. The Golding spar comes from Maine, the Eureka spar 
ties rightly balanced, r>or finer wares it is possible, nay it is r „ L . . , •, ,, „ ,, 
,. • ,, . ...... ' • from Connecticut, and both are very pure. For small quanti- 
lmperative that the same properties shall be imparted to the . , , . . • , , 
. , . r , . , ... , . ties it may be best to write to some potteries supply house as 
mix by the use of such materials as will supply them. T , ,,.. , - „ . . _ , „ TT , , ' . .. 
3 rr J John Wiarda, of Brooklyn, or Roessler & Haslacher, of New 
Just which quality shall predominate depends upon the Y ork city. The millers do not care to supply less than a bar- 
use to which the clay will be put. Modeling clay, for exam- rd of any one material) but j f there is storage space the bar . 
pie, needs the first alone. Plasticity is the only essential point rel of clay or flint js so much less expensive) that it is worth 
to be considered. Modeling clay need not be dried and never while to purchase . Besides in procuring materials by the 
goes to the kiln, therefore the properties of porosity and vitri- pound there j s a far greater dsk of variation from time to 
fication are unneccessary. Clay for the potter's use must be time 
plastic too or it could not be worked, but it must also be po- ~, . , . . . , . 
.... . . . . T ... , , r the necessary implements for mixing are a good sized 
rous or it will not dry or burn safely. It will thus be seen 1.1 • ; , . , . , 
iU ^ . . . , , . , . , , . mortar and pestle, a sieve of about one sixteenth inch mesh 
that plasticity belongs to the clay only, that porosity belongs , _ , . ... , . . , , ,.,,,, 
. , \r , , r_ ,-?■-■ . 1 1 - 7 and a fine screen of wire or silk bolting cloth, which should 
to both clay and pottery, and vitrification belongs exclusively , , . . , „, 
., , , ..,, ..... & J number 100 meshes to the inch. These screens cannot be 
to the burned ware. While both clay and pottery may pos- , , , , , . ' ., . ... , , , , , 
. fI1 ,1 ., bought ready made, but the cloth can be procured from deal- 
sess porosity it does not follow that the one is the conse- ... , , , . . , . 
f . . . . . ers in artists materials, and carpenters can make the frame. 
quence of the other, or that there is any connection between r> • , iU -i 1 r 1 <■ , 
,,.■ . ... . JtJesides these utensils, a number of vessels will be useful, and 
them. A very plastic clay may produce a very porous pottery , . ' , , ., . ., . „ .. 
. , ,,.,, . r „, a good pair of scales should be provided. Scales are exoen- 
and a very porous clav produce a highly vitreous ware. The . , . ■ . . ,. , , f , . , . r x , 
.... , r , , t , 1,1 , sive, but they are long-lived and bad weighing is the founda- 
addition of ground glass to a clay would be apt to render it , A , . . , . „ 
, ^ , . , ,,,,-,, , ■ tlon °' many errors. A good pair of scales is Froemner s 
quite porous, but the burned ware would be liable to melt in , , , ,, ° , w , , , 
/, r ™, . , ..„ , . . laboratory scales No. 7. They can be procured through chem- 
the hre. 1 he essential difference between clay and pottery is . , , , , . , ^ . ,,, , , 
^, ^ , , . . r , ■ , lca ^ dealers, and cost about nine dollars. Let the expen- 
that the tormer contains a certain percentage of combined , . . . , ^ 
, , , ., . . . . . r , . , . menter at once decide to use metric weights. Every recipe 
water which the latter has lost during the process of burning. , ,., . L L , . . _. f , , , , 
™, . , . , . , , , ■ , can be readily interpreted in fractions of one hundred, and 
Ihis combined water cannot be removed by drying alone, a , w , , ; . , , ... .",' 
..... ,. ,. ,., all the contusion ot pounds, ounces and grains is avoided. 
good red heat is necessary for its expulsion and once it has 
been driven off, it can never be replaced. Clay dried ever so Havin ^ now materials and a PP a ratus in working order, the 
hard in the sun is always susceptible to the action of water mlxin g ma > r be £ in - A g ood working body, pale cream in 
and a little soaking will bring it to a plastic condition. Burned color ' ma >' be compounded as follows : 
clay will not become plastic even when finely ground. There Florida clay 14 parts by weight 
is a close connection, therefore, between combined water and Excelsior Ball clay 20 
plasticity. Before burning, plasticity constitutes the bond Mayfield Ball clay 20 
. . , , 1, ' 1 • ■ i o 1 r , ■ , , • ■ Ground feldspar 40 " 
which holds the piece in shape. Some clays of high plasticity Ground Flint 6 
will dry so hard that it scarcely seems necessary to burn them. 
The fire, however, destroys this bond and unless another be 100 
supplied the resulting ware is very fragile. Every lover of Reviewing what has been already said, it will be seen that 
pottery knows the difference between a piece of well burned, this body consists of 54 parts plastic material and 46 of po- 
dense pottery and a flimsy morsel of baked earth which seems roU s, and that of the porous part 40 parts become vitreous in 
ready to fall to pieces from its own weight. Both may have the fire. The vitrification is further assisted by the fact that 
been alike before burning, but the fire has destroyed the the clays used are in themselves dense and close-burning, 
plastic bond, and the inferior piece had nothing to take its The mixture will prove sufficiently plastic for wheel work and 
P^ ace> coiling, and sufficiently porous for casting should that method 
A pottery body has been likened to the human body, be desired, 
consisting of flesh, bones and blood. The flesh is the clay The materials being weighed out, the spar and flint can 
substance, the bones are the silicious matter or ground quartz be at once run through the sieve, the clays must be pounded 
which gives rigidity and strength. The blood is the fluxing or i n the mortar until they too will pass through. The whole is 
melting property, the feldspar which, under the influence now mixed, a large vessel filled about half full of clean water 
of fire, flows through the pores of the clay and quartz, impart an d upon the surface of the water the mixture is scattered, 
ing vitrification, translucency, and consequent quality. handful by handful. The vessel should be left undisturbed 
In compounding a pottery body regard must be had to for a few hours, preferably over night, and the mixture then 
the degree of heat available. The temperature need not ex- thoroughly stirred. An egg-beater is a good implement for 
ceed cone 1, as it is perfectly possible to produce a vitreous "plunging" the clay and water, and the whole mass is now 
