Architectural Sculpture in The United States - The Production of Architectural Sculpture in Terra Cotta

The Production of Architectural Sculpture in Terra Cotta

Before the 1870s in the United States, architectural decoration was fairly sparse and largely consisted of wood or hand carved stone; these were both time-consuming and expensive. Experiments with terra cotta for this use were done in the 1850s; noted architects Richard Upjohn and James Renwick made the earliest use of the new material. At first there were technical difficulties and failures due to underfiring, as well as fierce resistance from stone cutters fearing loss of their livelihood. By the 1870s terra cotta was fast becoming the material of choice, as it was far easier to make, allowed for unlimited designs and could be made rapidly and inexpensively. Large sculptures and decorative schemes were divided into a multitude of blocks so that they could be reassembled by masons with mortar and metal cramps in place on the steel frames of the new architecture. This protected the steel from fire as well as the elements. The Chicago Terra Cotta Company, Midland Terra Cotta Company, N. Y. Architectural Terra Cotta Co., (Brooklyn 1886), Boston Terra Cotta Company (1880), Boston Valley Terra Cotta Company (NY 1889), Atlantic Terra Cotta Company, Gladding-McBean and many others began production of models, molds and finished ware for architects nation-wide. The process started with the architect's or designer's sketches and drawings; sculptors created original models in the factory, usually of clay and sized about 14% larger than the final product to allow for shrinkage. The architects approved the models or suggested changes to them. Once the model was approved, plaster piece molds were made of the clay models. At this point, in order to create many identical multiples, additional molds were made of the model or of the first plaster piece mold.

Properly formulated clay with grog (i.e., terra cotta clay body) was then hand pressed into these plaster molds. Average thickness was about 1½". Internal webbing and holes were also added by hand. Pieces were removed sometime later from the mold, once the clay had stiffened due to water absorption into the plaster and then finished by hand to remove defects and add more details. The model number and other identity numbers according to the blueprints were inscribed in the clay to guide the masons' installation of the pieces. Once dry, the clay pieces were fired in very large wood-fired and later- gas fired kilns usually over a three week period to a very high stoneware temperature. Various colored glazes and textures could also be applied to the visible surfaces if desired. Glaze increased the waterproofing quality, as did the (second) glaze firing.

• Circa 1895 terra cotta keystone.

• Back of a typical 1915 terra cotta keystone. Note the heavy internal structural webbing.

• Back of a typical sculpture showing incised numbering system.

• Multiple section terra cotta in the tympanum, a form used over windows and doors.