Making
Vases and Bowls
[Illustration]
MAKING VASES AND BOWLS is a little more complicated than the making of
tiles, but by following the directions carefully it will be found that
once the process is worked out, it can be easily repeated.
FOUR DEFINITE OPERATIONS are necessary to produce a bowl or vase and
they may be termed as follows:
1st. Making or preparing the original model.
2d. Making the molding case from the model.
3d. Pouring the concrete into the molding case.
4th. Releasing the mold and completing the object cast.
THE FIRST STEP, making the original model, is as follows: With clay or
modeling wax build a form of the vase or bowl desired. The inside need
not be considered; that is, do not make the form hollow but build it
solid. Care should be taken to see that the contour is even and alike
when viewed from all sides. A templet cut from metal, wood or stiff
cardboard, will help in securing perfect contour if moved around on the
outside and corrections made accordingly. A false neck should be added
onto the solid form and part of the bottom of the mold scraped so as to
leave a rim or edge on the bottom. The form is then ready to make a mold
from it.
ANY VASE OR BOWL CAN BE DUPLICATED in cement by making a plaster mold
from it. The inside of the bowl should be filled with sand or wadded
paper and a false neck built over the mouth with clay or modeling wax.
If the surface is glazed it need not be oiled before casting, but all
dull or rough surfaces should be oiled.
THE SECOND STEP, making the molding case, is as follows: Take the model
(clay or vase to be duplicated) and place it upon an oiled glass or
other smooth surface. Marking off about one-third of its diameter, build
a narrow strip of clay or wax on two sides from top to bottom. This
ridge or wall should extend far enough out to meet the molding case or
metal strip, and the two walls of clay and the metal or case should be
made proof against the plaster running out anywhere, when it is poured
into this well. After the plaster is set, the clay strip can be removed
from one side and the exposed plaster edge is oiled after two keys have
been bored into it with a pointed metal strip (see working plate). The
removed strip is then built along the next division of the model and the
case or metal used for retaining wall is moved into new position and a
second third of the molding case is made. To make the third or last
piece of the mold the two first sections are retained in position
(always boring keys and oiling exposed edges), the case or metal wall
again placed in position and the plaster poured into the opening. The
plaster should not be too thin and if a little is poured into the bottom
and allowed to set before pouring the whole amount, it will not be
forced out through the bottom. Of course all openings must previously
have been stopped with clay or wax.
TO STRENGTHEN A MOLD strips of burlap or wire screening can be imbedded
in the plaster while it is soft. This makes a durable mold capable of
withstanding much handling.
TO MAKE THE MOLD FOR THE BOTTOM the three sections are turned upside
down (the model still being in position) and the plaster parts all being
oiled, a ring of clay is placed around the bottom so as to make a cup
shape into which the plaster is poured.
THE THIRD STEP is the most important part as the mixture or “slip” for
the pouring is important. The first mixture should be neat cement and
water and should be rather thick, for if too thin it will not adhere to
the walls of the mold. When the neat cement is ready it should be poured
into the bowl about half-way full. The bowl is then rotated in a
horizontal position gradually downward so that the surplus cement slip
will pour out of the mouth back into the pan or container in which it
was mixed. Then after a half-hour or so another mixture of slip should
be rotated. This mixture should be composed of a one-third cement and
two-thirds sand mixture and be thinner in consistency. If the bowl is
large and the walls need to be thick a third and fourth layer may be
necessary.
THE LAST LAYER OF SLIP can be of neat cement which will finish the
inside with a smooth surface. When working with color the first rotation
and the last may have color added to the slip which will result in a
color finish on the inside and the outside of the bowl or vase.
THE FOURTH STEP or releasing the mold, should occur the second or third
day after the pouring has taken place. This elapse of time depends all
upon weather conditions. In summer cement dries more rapidly and not so
well. In winter the hardening is more slowly accomplished but more
perfectly.
THE DRYING OF CEMENT is best when it occurs gradually. Never place
cement in the sun or use artificial heat to force it. Checking, cracking
and breaking will surely result if this is done.
For this reason the tiles and pottery made with cement should dry
gradually in the shade but not in a draughty location.
To release a vase or bowl from the mold, the cords are untied and the
plaster mold parts opened. The cement cast, if successful, will separate
from the mold without trouble. The ridge that may have been formed by
the groove where the plaster parts have come together can be scraped off
and smoothed by rubbing the finger tips over the surface. The surplus
part of the neck can be carefully scraped away and after the vase has
dried out of the mold for a day it can be put in a bucket or tub of
water to harden for a few days or a week.
TO FINISH A VASE it is removed from the water, permitted to dry well,
the surface is brushed clean and it can then be waxed or surface
finished as described in another chapter of this book.
A RELIEF DESIGN ON A VASE SURFACE requires care in making the sections
of the mold so that the vase cast will pull out of the mold without
breaking. If the molds are made in three or four segments there is
little danger of trouble but wherever there is relief surface or lines
on the surface, a two-piece mold is sure to result in the breaking of
parts.
DIFFERENT TEXTURES IN GRAY CEMENT can be secured on the surfaces of
bowls and vases by using almost any of the processes described in the
previous chapter for tiles.
IN ADDING COLOR TO DIFFERENT TEXTURES of cement in Cement Pottery the
color or neat cement can be added to the oiled surfaces of the plaster
molds before they are tied together preparatory to the pouring. In this
instance, however, the divisions of the plaster molds should be planned
so as not to break through the designs. If a continuous design motif is
essential, the only way to correct the break will be to touch in the
disconnected parts with the right color or mixture after the parts of
the mold have been placed together just previous to the pouring in of
the slip for the first rotation.
THE MAKING OF FLAT BOWLS simplifies the rotating problem and in many
shapes the slip can be placed and directed with the use of a brush.
After the last slip has been added to a bowl, a design can be added with
a brush by using a different color, placing the color slip in the center
of the inside portion of the bowl. This can also be done on the outside
surface of any bowl or vase, creating a change and surface enrichment.
VASES WITH SQUARE SIDES should be produced from plaster molds which have
the connecting lines coming on the corners. In this way the casting
lines that always show to some extent on the cast surface when it is
removed from the mold, will occur where it will be easy to remove them
and if a little does remain it becomes a part of the corner.
If any incised lines or relief parts are on the sides of these square
formed vases, a separate piece for each side will be necessary in the
plaster mold.
A GLAZED FINISH can be produced by rotating a bowl or vase in a mixture
of neat cement that has been well sifted and placed in a pan in a thick
enough layer to permit the bowl or vase to be turned in it without the
sides scraping the bottom of the pan.
WHERE LARGE RELIEF SURFACES are to be produced and undercut surfaces
molded, it is then necessary to use glue for the molds. This requires
skill in handling. For those who wish to produce molds for such work the
following is given:
After modeling the surfaces or figures in relief, if they are to be used
on garden pottery, book-ends, vases, etc., or any design that has
undercut surfaces, it should be covered over entirely with a one-half
inch layer or blanket of wet clay or modeling wax. If the modeling has
been done in clay it should remain overnight without the usual wet cloth
over it, before placing this second clay layer. If wax is used the clay
layer can be placed over it without waiting. Deep sections should be
lightly filled with clay to reinforce the one-half inch layer. Two or
three nails should be used to hold the original firmly to a board base.
A little plaster-of-Paris should be poured around its base to help make
it firm.
Over this clay blanket lay a strip of clay along the highest part or
equator of the surface, so that the surface is directly in line with the
equator. Place a casing around and fix so that plaster can be poured,
and a rough casing produced of one half. Remove the clay strips and with
a pointed piece of metal bore several holes or “keys” in the exposed
edge of the plaster. Oil this edge and cast the second half.
Before pouring the plaster a clay cylinder should be placed at the top
to form a hole for pouring into and a second hole near it for an air
escape.
After the plaster is set it will be found that a casing or shell is
produced which when placed over the original model (the one-half inch
clay blanket having been removed) will leave a space around the entire
original model.
The next step is to prepare the casings and pour the glue into this
space to produce a mold of the object and its immediate surface.
A few pencil marks are made on the outside of the casing and carried
onto the table or board base to check up its relation when it is
replaced. These marks are very necessary.
The casings are then given two coatings of shellac and wood alcohol (one
part alcohol, three parts shellac), and when dry are oiled well or
greased with axle grease. Shellac is also applied to the original model
whether clay or plaster. Plasticene or similar wax need only be oiled
slightly.
Replace the cases so that the two halves come together closely and so
that the marks on the outside lower edge correspond correctly with the
marks on the table. Stop the cracks on the casing with clay dipped in
plaster and bind over the casing in the same way (or with the use of
cords) to prevent the glue from floating the casing.
THE GLUE IS PREPARED as follows: White fish glue or gelatine glue is
washed well in water. Put in dry can, placing it in second pan of water
and boil until creamy in consistency. When the finger can be dipped into
it without burning, the glue is poured into the casing as follows:
A funnel of clay or wax is roughly made and the glue poured into the
opening of the casing, filling the space between the model and the
plaster casing.
Let stand for twelve hours. Remove casing and cut the glue shell along
the half-mark made by the equator division, cutting from the under side
through at one stroke. The glue can be lifted (as it will give) so as to
permit cutting from underneath. To cut from the outside will not produce
a clean cut.
With French chalk or talcum, chalk the inside of the plaster casing well
over the shellac and fit the glue shells back into each half. Then with
a solution of powdered alum and water (two teaspoonfuls in one-half cup
of water) brush the entire inner surface of the glue to harden the
surface. Let stand for one hour.
IF CEMENT IS TO BE USED, the glue must receive two coats of white lead
or varnish and left to dry two days. When plaster is used no white lead
or varnish is necessary.
Cement should be used thin and a thin layer produced by pouring into
this mold and revolving it so that a coating will stick to the surface.
After setting for twelve hours more is added and again revolved until
the desired thickness is produced.
Where the object is not to be hollow the cement is poured in solid and
left until hard enough to remove the casing and glue shell.
This sounds complicated but it is no harder than the usual recipe and if
you can’t follow a recipe or be interested in its result, then there is
no hope for you in Color Cement Handicraft.
A DIAGRAM ILLUSTRATING GLUE MOLDS is shown at the end of Chapter Two, on
The Making of Plaster Molds. A little study of this with the above
directions will make the process clearer.
[Illustration: Vase Molds]
[Illustration: The Finishing of Cement Pottery]
[Illustration]