Now an examination of the designs of these buildings will, I believe, divide them into two classes.
First.—Designs in which terra-cotta has been used as a stitute for stone.
Second.—Designs in which terra-cotta has by its facility of formation furnished the architect with a freedom of expression that enabled him to give scope to his fancy and produce re sults impossible to the school of line, square and plummet. The further fact will also become apparent, viz : that much of the recent great advance in freedom of design in this country began with the advent of the architectural terra-cotta worker.
When the use of burned clay in other forms than common brick was suggested to our architects, they at once gravitated towards two distinct ideas: 1. Terra-cotta as a substitute.
2. Terra-cotta as a distinct " building material." Some architects were attracted by the hope of having found a cheap substitute for stone, which would enable them to get more show for less cost. Such architects would ask for large pieces, rock surfaces and stone colors. They would select a chip of natural stone, and demand that the clay-worker do an impossibility, viz.: reproduce that exact shade of color, ignor ing the fact that the color of the stone is in z great measure due to the texture of its surface.
Stone work always presents a section of the material and shows the grain, while terra-cotta always presents an outer skin produced by the concentration of the finer particles of the clay at the surface of the mould in pressing the material into the de sired shape. In stone the carved work differs in color from the plain surface. Yet the material is identical.
As to uniformity of color in terra-cotta, it can only be ob tained in one way, and that is available—let the painter have a chance.
The pursuit of cheapness never yet had any artistic value ; therefore it is useless to expend thought on the question of terra-cotta as a substitute or sham building material. Terra cotta is a valuable material; it has a practical utility and is capable of artistic expression in architecture. It is the materi alized crayon sketch.
The proper use of terra-cotta demands : i. Moderate size of pieces.
2. Manipulation of the surfaces.
3. Consideration in the eonstruction.* 4. Protection of the exposed joints.
5. Freedom of shade in color.
It must always be remembered when making designs for execution in terra-cotta that the material is plastic during all the processes of manufacture. It has to be pressed into plaster
moulds to give it the desired form, then it has to be dried be fore it can go into the kiln, during which processes it will con tract and lose about one-twenty-fourth of its bulk and one twentieth of its weight. This shrinkage continues during the process of burning, and makes the total contraction about one twelfth and the reduction of weight about one-fourth. If the size and form are moderate, this shrinkage will be obtained without cracking or distortion and with but small risk of failure. The same conditions affect the surfaces of the material ; unequal drying causes varied contraction, which the high light of sun shine apparently magnifies ; therefore terra-cotta should never have a smooth surface for exterior work. Many treatments of surface are in vogue, such as tooled, combed, stippled and crinkled finish ; all of these are used to convey the idea of a soft and plastic material.
The use of terra-cotta sometimes leads to great errors in construction. It is customary to speak of terra-cotta as being light in weight ; but this is only true in regard to transportation of the surfaces, for when terra-cotta is set in place and properly filled (so as to preclude the formation of pockets of water, which means ice in winter), it becomes the same actual weight as brickwork and very much of the same construction, therefore all excessive projections, spans or openings ought to receive a good and sufficient backbone of iron construction.
There are instances in New York City where cornices with three feet of projection are simply covered with inverted boxes of terra-cotta, each box capable of containing many gallons of water, and at about every two feet there is a convenient joint, which, when the pointing becomes a little loosened (as it will), will freely admit the rain water and let it soak into the walls, so that in the winter time ice will be formed in these boxes and breakage may result. Surely this is not the fault of the terra cotta, though the material is often blamed in such cases. In a a climate of such extremes as ours, it is evident that all upper surfaces which are traversed by joints ought to be covered by some sufficient protection.