The generation of Hepplewhite-style chair-back designs

A parametric shape grammar is given for the generation of Hepplewhite-style chair-back designs. Introduction "To unite elegance and utility, and blend the useful with the agreeable, has ever been considered a difficult, but an honorable task. How far we have succeeded in the following work it becomes us not to say, but rather to leave it, with all due deference, to the determination of the Public at Large" (Hepplewhite, 1794). The great epoch of English cabinetmaking reached its zenith during the last half of the eighteenth century. Yet, the aesthetic appeal and functionalism of a Chippendale, Hepplewhite, or Sheraton, for example, is still compelling and being imitated nearly two centuries after the original designs were created. Interestingly though, the formulations of furniture designs in the eighteenth century were based on design standards quite different from those embraced today. During the late 1700s, guidebooks or catalogs were published by the more prominent and influential cabinetmakers for the purpose of providing other cabinetmakers and designers with a wide variety of formal models on which to base their own designs. As Greenberg (1977, page 72) notes: "The drawings in the handbook explore interrelated series of formal variations based on a given set of themes .... Each aesthetic theme has a base model, the ; simplest form of the model, and by using different degrees of formal, ornamental, metaphorical, and structural complexity, an appropriate design solution could be developed. Rather than justify the base models, the handbooks document a few design variations." Thus, "Design was understood as a process of refinement requiring the development of increasingly rich and complex solutions based on accepted models .... Innovation is largely restricted, therefore, to the development, in ever more brilliant designs, of already stated themes" (Greenberg, 1977, page 75). The result of this type of design methodology is a highly developed language based on a particular model or paradigm. Creativity is expressed not by innovation of new paradigms or novelty as is so often encouraged and rewarded today. It is expressed by elaborations on the given paradigm within the context of the language which defines it. Good design, therefore, is a reflection of the designer's ability to fully understand this language and to develop its potentialities in an articulate and refined way. In this paper, three examples of the Hepplewhite-style shield-back chair are studied, in particular the design of the back itself, and traced to a common base model or paradigm. Given this paradigm, a parametric shape grammar (Stiny, 1977) is developed which defines its unique characteristics and constraints. The grammar specifies shape rule schemata which generate not only the three designs in the original corpus, but also a wide range of new designs within the constraints of the paradigm. 228 T Weissman Knight Like the guidebooks of the eighteenth century, the grammar is the design tool by which new solutions can be developed based on a given model. The language of Hepplewhite-style chairs defined by this grammar can be seen as an extension of the catalog of designs compiled by Hepplewhite himself. The shield-back or heart-shaped chair was the design which brought Hepplewhite his greatest reknown, The pattern of the back is invariably composed of smooth, unbroken curves richly ornamented with familiar neoclassical motifs such as urns, medallions, and festoons of drapery; the seats are usually square and the legs tapering. It is the design of the backs however, which allows for the greatest variation in style, while at the same time adhering to easily discernable and well-defined regularities which uniquely identify a chair as being 'Hepplewhite'. In fact, it is the design of the chair-back alone which so strongly differentiates a Hepplewhite chair from a Sheraton chair, for example; the legs and the seat being almost identical. The three examples of a Hepplewhite-style shield-back chair (figure 1) shown below are attributed to the American architect and furniture designer, Samuel Mclntyre, a close contemporary of Hepplewhite and a leading exponent of his work. With the exception of slight differences in ornamentation, the chair-backs shown in figures 1(b) and 1(c) are direct copies of chair-backs designed by Hepplewhite. As will be shown, all three chair-back designs can be said to exemplify a particular design paradigm within the Hepplewhite style. In the following sections, this paradigm will, first, be analyzed and described by distinguishing certain characteristics common to and expressed by the three chair-back designs. These unique characteristics will then form the basis for development of a parametric shape grammar which defines the paradigm and gives schemata to construct new examples of it by generating simple rectilinear patterns. Finally, a procedure is given which translates these basic rectilinear patterns into curvilinear designs consistent with the Hepplewhite style. The chair-back designs generated by the grammar and procedure give only a partial description of a Hepplewhite shield-back chair. The design of the seat and the legs and the carved ornamentation, also uniquely 'Hepplewhite', is not dealt with here although equally amenable to definition by a grammar.