Color Cement Handicraft 9

Color Cement Handicraft 9

TO CAST THE PLASTER MOLD the clay or modeling wax is surrounded with the

retaining bars and as the clay or wax needs no oiling the plaster can be

mixed and poured into this mold. A slight jarring of the table or

surface on which the mold is placed will cause the plaster to settle,

producing a level surface and also cause any bubbles to break or come to

the surface.

 

TO AVOID BUBBLE DEFECTS IN CASTING either with plaster or cement the

plaster or cement mixture should be poured into the center location of

the mold allowing it to spread gradually toward the sides and corners

carrying the air in the grooves and low spaces, forcing it toward the

edges. Once the surface is covered in this way the remainder of the

mixture can be poured in more rapidly.

 

TO CORRECT BUBBLE DEFECTS that appear on the finished plaster or cement

casting, scrape some of the plaster or cement from the back or sides

where it does not matter and repair the flaws by pressing it into the

holes. Where cement is repaired this way it should be permitted to dry

for another day before it is placed into water to harden.

 

TO MAKE THE CEMENT RELIEF TILE in color the plaster cast made from the

clay or wax model should be oiled after it has been shellaced and

surrounded with the retaining bars. The color should be then mixed with

the cement and water added to make it of a pouring consistency, it is

then poured into the mold. After this color has set for awhile the back

layer is added of concrete after the color of the first pouring has been

carried up so as to produce color on the sides as well as on the face.

 

WHERE A NUMBER OF COLORS ARE USED the colors are mixed and dripped upon

the oiled surface of the plaster mold before it is enclosed with the

retaining bars, as the retaining bars would prevent free access to the

surface with the brush. After the various colors have been placed, the

plaster cast is then placed within the bars and the color being

permitted to set, it is then backed with a layer of concrete.

 

THE CONCRETE BACKING MAY BE COLORED either with color throughout or with

a topping of color to give it a finish. If corners are to be rounded or

the edges trimmed in any way this color layer should be thick enough to

permit trimming without exposing the under layer.

 

TO AVOID THE COLOR FALLING OUT in color relief work, the following

should be observed. When preparing to pour in the backing, observe

whether any of the color cement placed on the tile has become too dry.

If so, it should be sprayed with a light coating of water or brushed

with a brush full of water, and its upper exposed surface slightly

roughened so that the backing will adhere firmly. If it becomes dry and

smooth the second layer of cement poured onto it will come in close

contact but not adhere, and later a change in temperature or jar of the

tile may shake a portion of the design loose so that a color fragment

will fall out.

 

TO AVOID COLOR PREMATURELY DRYING, the plaster cast should be placed in

water for fifteen minutes at least before the color is placed into it.

To permit free absorption of water the plaster tile should never be

shellaced on the bottom but only on the sides and the top.

 

ANOTHER WAY TO MODEL A RELIEF DESIGN is to carve it on plaster direct

without making the relief on clay or modeling wax. This method has the

advantage of being proof against overhanging edges, though some care

must be taken against undercut surfaces.

 

TO MAKE THE PLASTER CARVED MODEL trace the design onto a smooth slab of

plaster of the right size that has been cast on a smooth surface. If a

larger piece of plaster than the desired size is used it can be cut

down.

 

TO CUT PLASTER SECTIONS an old saw can be used or several strokes of a

knife on the surface until about one-quarter of the thickness has been

cut, and a similar cutting on the reverse side, just opposite to the

cutting on the first side will enable the plaster to be broken easily.

Or by laying it on a straight edge with the line of cutting over the

edge, a quick pressure with the hand will snap the two pieces apart.

 

AFTER THE DESIGN IS TRACED a chiseled nail point, nut pick or other hard

edged point is used for scraping the surface of the plaster, modeling it

or carving it to the desired shapes. Naturally it will be found that

plaster can only be taken off and not added on and that all reliefs

must be produced from the surface downward, that is the natural surface

will be the maximum height and all variations in the surface produced

below that.

 

BACKGROUND TREATMENTS are produced where a design appears in low relief

against a background. The background may be stippled with the tool point

or lines scraped or crossed lines used to create interesting background

qualities.

 

TO BUILD UP PLASTER SURFACES, roughen the surface onto which more

plaster is to be placed and mix fresh plaster and place it on with a

small spoon or with the brush. After this is dry it can be carved or

scraped with the tools used in the modeling of plaster.

 

TO FINISH THE PLASTER CARVING, it is dried, shellaced, and used for

casting just the same as the other relief forms described. To preserve

casts from receiving injuries to their surfaces they should be wrapped

in paper with a card against their face and placed with face toward the

wall in a cupboard or shelf, when not in use. Where a mold has been

repeatedly used and the shellac become worn, the mold should be

carefully dried and the shellac coating renewed.

 

A CONVENIENT CLAY TO USE for relief work is the powdered fire clay

secured in most hardware stores and is the clay used for lining grates,

furnaces and similar purposes. This clay is convenient in that only the

amount needed may be mixed up for use, leaving the balance of the

powdered fire clay always in good condition.

 

RELIEF TILES DESIGNED FOR FLOOR SURFACES or for wall surfaces are best

where they do not contain deep relief as they will not catch dust or

dirt and will be better unified with the remaining surfaces.

 

SPECIAL TREATMENT FOR RELIEF FLOOR TILES is required in that the cement

should be compact and clean sand should be used mixed with just enough

water to cause the two to adhere to each other and this should be

tamped into the mold well up against the face of the plaster tile to

pack the mixture firmly and cause it to form into a durable surface.

 

TO HARDEN CEMENT TILES or pottery they should be placed in water so that

the water will complete the chemical action producing the stone-like

quality of successful cement work. If the tile is removed and dried and

again placed in water it will increase the hardness.

 

AFTER THE TILE IS HARDENED it is dried thoroughly and brushed well with

a brush. It may be waxed or first given a thin coat of shellac and then

waxed. Shellac should never be applied until the cement tile is

thoroughly dry, as otherwise the shellac will remain sticky.

 

[Illustration: Plaster and Clay Modeled Cement Tiles]

 

[Illustration: Color Cement Tiles and Pottery by Art School Students]

 

 

 

 

[Illustration]

 

CHAPTER 7

 

The Majolica Tile

 

[Illustration]

 

 

MAJOLICA POTTERY derived its name from the island of Majorca, Italy,

where during the sixteenth century glazed pottery reached its highest

perfection.

 

Glazed color may be placed in hollows in the surface of pottery or on

the surface. A better method is to produce a raised line or rim to

retain the glaze, and this is the method we will use in the cement or

concrete pottery.

 

THE CEMENT MAJOLICA TILE is made as follows: First design a subject that

will have each motif, part or section defined with lines. These lines

must be part of the design and used much as lines are used in stained

glass work. The design should be simply planned. A confusing

overcrossing tangle of lines is to be avoided. A few geometrical forms

rightly related will be most pleasing. Keep the design at least one-half

inch within the edge of the space. Then oil a piece of glass as

directed, place over a card that has the tile dimensions squared off on

it as a guide for placing the casting bars on the glass. Clay or wax

should always be used to hold the casting bars in place. Into this now

pour plaster-of-Paris, pouring into the center, letting it flow to the

outer edge. Level off evenly and remove after fifteen minutes. On

releasing this plaster tile a smooth surface will be found on the side

which came next to the glass.

 

THE DESIGN is then transferred to the plaster tile by tracing with a

carbon paper. The paper should be thumbtacked onto the sides of the

plaster tile to prevent it from slipping while tracing. The design

should also be traced on backwards so that the completed majolica tile

will be in the same position as the design. The design is then incised

with the incising tool, care being taken that at whatever depth the line

is made the incision has sides sloping upward. If these grooves have

overhanging edges the cement to be poured in will flow under these edges

and lock the tile, causing these lines to break before the cement tile

can be released.

 

WHEN INCISING, see that the bottom of the groove is sufficiently wide,

as this bottom is to be the surface of the line on the completed

surface. A line one-sixteenth or one-eighteenth of an inch is not too

wide. The plaster should not be too soft or too hard to secure the best

incision and avoid crumbly lines. When the incising is completed oil the

surface and surround the tile with four retaining bars. The bars should

be soaked in water and be of double width as they extend above the

plaster cast. This extension above the tile represents the thickness of

the tile to be made. Clay or wax is pressed on the outer edges of the

bars and plain neat cement or a mixture of the desired color is made and

poured onto the mold. Pour in the center steadily, for cement poured on

the “installment plan” will show a mark wherever each installment

occurred.

 

When the cement in the mold has dried for twenty-four hours remove by

slightly prying, after the retaining bars have been removed. If parts of

the lines are not on the surface it is because air was arrested in

pouring the cement or the oil settling in the grooves. If lines are

broken and remain in the mold it is because the grooves have overhanging

edges and locked the cement line. To repair these lines, soak the tile

for a few minutes and mix a small portion of cement to match that used

and build the missing section by dripping the cement from a brush.

 

AFTER DRYING for an hour put the whole tile in water for a day or

overnight and it is then ready to add the color. Meanwhile the plaster

mold with the defective grooves should have the grooves cleared by

scraping the overhanging edge with an incising tool.

 

The tile as it has been produced by the mold appears with a number of

relief lines dividing the whole surface into a number of partitions or

cells. It is into these that we are to place the color and it should be worked as follows: