The long eighteenth century was a turbulent period in France, many crucial reforms in society, politics and art challenging the established order of the ancien régime. This battle took place on the theatrical stage as well and materialized in the approach to costume. The present thesis examines the development of theatrical costume – especially for opera and ballet – during this period, with particular focus on the so-called costume reform. Who were the main personalities of the reform and what were their arguments? How did it relate to the artistic and social context of the period? And most importantly: how did the new ideas materialize in practice? In order to explore these issues, the work of Louis-René Boquet (1717–1814), the leading costume designer of the French court and the Paris Opéra, a collaborator of the fairground theatres and the reform choreographer Jean-Georges Noverre, is used as the main reference point.

In accordance with recent theoretical approaches to costume research, formulated for instance by Aoife Monks, Anne Verdier, Donatella Barbieri and Veronica Isaac, costume is regarded as a specific object within theatrical practice, and as a crucial agent in the production of the body on stage. This helps to define eighteenth-century costume as a crossroads where aesthetic, social, dramaturgical and physical requirements met and negotiated. Drawing on a wealth of textual, visual and material evidence, the methodology applied in the research combines approaches from material culture studies and theatre studies, including practice as research, connecting aesthetic theory with the analysis of performance and sartorial practices.

The thesis is divided into two parts; the first part investigates mainly the theoretical discourse around costume, and the second part focuses on the making and agency of the costume in the context of theatrical practice, particularly at the French court, at the Paris Opéra and in Stuttgart, investigating the development of the reform through Boquet’s work. Two concepts of costume are defined and discussed, one driven by the ‘aesthetics of propriety’, which includes the (courtly) social proprieties of dress within the concept of verisimilitude; another driven by ‘aesthetics of truthfulness’, which views the stage as a tableau, therefore requiring a depiction of dress from different periods and locations similar to that in paintings, but also a costume that is adapted to the dramatic situations of the characters. The latter defines the movement of the reform. However, this thesis suggests that we should distinguish between two phases of the reform: a moderate ‘first wave’ (1750s–1770s) and a more radical ‘second wave’ (from c.1783). Focusing particularly on the pioneering ‘first wave’, and investigating costume strategies for various genres, themes and characters, this study shows how the first reformers negotiated with the older conventions and changing fashions, how they insisted on the specificity of the theatrical costume, and the extent to which the practices of the popular stages influenced those of the serious genres. Boquet’s work, previously considered conventional or ‘unreformed’, is shown to embody the different stages and issues of the reform: a unique example of the dynamic development of costume in the second half of the eighteenth century.