There are two methods of making tiles, the dust-pressed method and the
plastic. The former is the more usual commercial plan but the appliances
for preparing the dust and the heavy presses necessary are not adapted
to studio work. The dust-pressed tile is, moreover, somewhat mechanical
in surface. It is not suitable for modeling or for any treatment but
those of glaze and color. The plastic tile, on the other hand, may be
treated by plastic methods and the surface offers a texture which
appeals strongly to the artist.
For the successful production of tile a special body is necessary.
Ordinary pottery clay is too close in grain and straight tile cannot be
made from it. Small square pieces, however, such as tesseræ, can be made
from any clay.
It is presumed that a pure white tile body is not required. For studio
work the most pleasing white surface is found in an opaque enamel, but
for the most part the craftsman will wish to work for colored tile. A
cream or buff body is all that is necessary, therefore, and the
foundation of this is a clay known as sagger clay. In order to secure
the necessary porosity a fine "grog" must be used. Grog is burned clay.
After working awhile there will be an abundance of this in broken
unglazed pottery but at first some soft fire-bricks must be pounded.
This is laborious work, but a boy can usually be hired to do it. The
brick or broken pottery is crushed in an iron mortar but should not be
broken too fine. Two sieves are necessary, one of 20 and one of 40
meshes to the linear inch. The coarse powder which passes through the 20
mesh and lies upon the 40 mesh is used. This is called 20-40 grog. The
dust which passes through the 40 mesh may be saved for kiln work. It is
useful for setting biscuit pieces one upon another as it will
effectually prevent sticking. This powdered grog is also useful in the
case of flowing glazes. A thick layer on the bottom of the kiln will
catch any drops of glaze and save the kiln from damage.
A quantity of the 20-40 grog having been prepared, a mixture should be
made of:--
Sagger Clay 550 parts
20-40 Grog 300 parts
Ground Flint 150 parts
The clay should be finely pulverized and the whole mixed in the dry
state. Water is then added, little by little, until a rather soft mass
is obtained. It is not practicable to mix clay of this description by
the slip method because the grog would settle out and fall to the bottom
of the vessel. It sometimes happens, however, that the stoneware clay
contains grains of iron which cause black spots to appear in the tile.
If these cause trouble the clay must be made into slip first and lawned
through 120 mesh. It is then allowed to become very thick and the grog
is stirred in. This is a good deal more trouble than the first named
plan and is not often necessary.
Tile are sometimes made in plaster molds. A tile of the proper size is
cut from a plaster block and a mold is made from it. If a modeled
surface be desired clay may be modeled upon the face of the plaster tile
before the mold is made. The mold will then receive the embossment in
reverse and all the tiles made from this mold will be alike. The clay is
pressed into the mold while quite soft and is scraped off level at the
back. Thus it is the face of the tile that is shaped by the plaster. If
this plan be adopted the tile must be removed from the mold as soon as
possible. If left to dry in the mold they will warp because of the
unequal absorption.
A better method has been devised by the author and has been put into
practice with considerable success. When the size of the proposed tile
has been determined a board is made which is large enough to hold a
square of the tile, say twelve or sixteen. Thus if a tile five inches
square is to be made the board would be fifteen by twenty inches for
twelve tile or twenty inches square for sixteen. On each side of the
board a wooden rim is fastened and this must stand higher than the board
to the exact thickness of the tile. About five-eighths of an inch is
enough. The board must be perfectly rectangular and marked off at even
distance of five inches and a shallow groove is cut at each point.
To make the tile the board is wetted and an even coating of grog dust is
sprinkled upon it. A ball of clay is laid in the center of the board and
rolled out with a rolling pin to fill every part of the frame. With a
straight edge the clay is struck off smooth and clean, working always
from the center outwards. Reversing the plaster mold method the tile are
now face upward and any kind of surface may be given at will. The clay
may be lubricated with water and made smooth or it may be sprinkled with
grog dust which will give a sandy or toothed finish. The square is now
to be cut into tile and this is done with a slender knife and ruler. The
ruler should not rest upon the clay but upon thin strips of wood or
cardboard which may be laid along the edges for the purpose. The cutting
should not go quite through the clay as, if a slight connection be
allowed to remain at the bottom, the tile will keep each other straight.
When the cutting is finished the board should be set at an angle of
forty-five degrees for the clay to harden. When leather-hard the whole
may be turned gently over and the tile allowed to fall on to a board
placed in readiness. They are now broken apart, trimmed if necessary and
set aside to dry.
Tile made in this way can be kept straight without difficulty and the
method is much more expeditious than pressing in plaster molds.
If a modeled surface be intended it is quite easy to work on the tile in
the tray while the clay is soft. Forms may be cut in wood and pressed
into the clay in any variety and the charm of individual treatment is
preserved.
The body given above will prove quite porous when fired but it will take
matt glazes well. A little crazing is no detriment to tile because they
are not like vessels which are meant to hold water. If a denser body be
wished for some of the flint may be replaced by spar.
One of the most attractive methods of decorating tile is by means of a
white or delicately tinted enamel and color. The opaque tin enamel given
on page 134 will answer well and if the whiteness prove too intense it
may be modified by a very small addition of under-glaze color according
to the tint desired. The tile should be glazed rather thick. Not as
thick as a matt glaze but thicker than bright glazes. The glaze or
enamel should be poured into a flat tray which is large enough to
receive one tile. The tile is taken by the edges between fingers and
thumb and held face downwards. Do not let either fingers or thumb
project beyond the face. The glaze having been well stirred the face of
the tile is allowed to rest upon it for about two seconds. The hand is
then lifted quickly and reversed so that the tile is face upwards. Every
effort should be made to avoid streaks or tears and a little practice
will accomplish this. If the glaze shows a bad surface it should be
scraped off. It can be mixed up and used again. Sometimes a slight
wetting of the tile before glazing will help the surface to flow evenly.
The decoration is carried out with ordinary under-glaze colors. These
may be mixed together to produce any hue which is sought and a little of
the glaze itself, about ten per cent., should be mixed with the color.
This will assist in uniting the color with the glaze so that they melt
together.
To produce enamel decorations at their true value the color should be
painted upon the dry glaze before it is burned. The best relation
between surface and color is thus secured. The color must be worked
quite thin with water and a little glycerine. A quick, sure stroke is
needed as no change or erasure is possible. The design may be made on
paper and traced or pounced on to the glaze with lamp-black.
For burning the tile there is nothing better than little fire-clay
boxes. These can be made in a mold without difficulty and the inside of
each should be washed with glaze. If some such protection be not
provided dirt is almost sure to fall on the flat surface and the tile
will be spoiled. It is not possible to rear them on edge in the kiln for
burning as then the glaze would flow to the lower side and cause an
unsightly ridge.