altarpiece would eventually be seen. As the Getty modello for the ceiling of Santa Maria degli Scalzi (cat. no. 8) demonstrates, oil sketches could even play a role in the dialogue between Tiepolo and other collaborators, such as Giro- lamo Mingozzi Colonna (ca. i688-ca. 1766), whose illusionistic architecture often accompanied Tiepolo's frescoes. Works retained by Tiepolo could also enjoy a second life as a salable commodity, such as the sketches sold to the 18 Swedish collector Count Carl Gustav Tessin. He also regularly gave away oil sketches as gifts to clients, colleagues, and friends, such as the works Tiepolo presented to his great advocate, the critic Count Francesco Algarotti.19 Sketches made as ricordi, or copies after the original composition, re- 20 main controversial. That Tiepolo's studio made such copies is not in doubt, but scholars disagree as to whether Tiepolo would have produced such works himself (although the high quality and poised handling of the oil sketch rep- resenting a ceiling from the Palazzo Archinto in Milan [cat. no. 4] surely comes from Tiepolo's own hand). At the same time, many ricordi are clearly studio copies, exercises Tiepolo—to judge from the number of such works in circulation—enthusiastically encouraged, both as records of projects in far- flung locations and as part of his pupils' education. These copies evidently enjoyed a large resale market, and his sons Giandomenico (1727—1804) and Lorenzo (1736-1772), as well as another pupil, Giovanni Raggi (1712- 1792/94), emulated his oil sketches with convincing, salable results.21 Collecting Oil Sketfaes 22 Most oil sketches—like drawings—remained in painters' studios. These paintings served as pedagogic tools, guides for realizing a larger composition awarded to the studio, or j ump ing -off points to develop related compositions, practices often continued after the death of the master. Ap- preciation of oil sketches by art collectors began in the early seventeenth century and swelled over the next two hundred years. The transformation of 3 these paintings from artists tools to treasured objects was inextricably tied to the growing understanding of oil sketches as distillations of an artist's unique genius. The excitement of the fresh, painterly surfaces became an end in itself, and the works were prized for their closeness to the hand and mind of the artist.23 While many collectors competed for oil sketches by Rubens, such broad enthusiasm for modelli by other artists remained unusual at the beginning of the seventeenth century, and a small number of figures, such as Carlo, Leopoldo, and Ferdinando de' Medici, as well as Pietro Aldobrandini, domi- nated the market. Even for these well-known collectors, oil sketches played a relatively minor role in their overall patronage. Symptomatic of this dis- regard, the seventeenth-century theorist Gian Pietro Bellori ignored oil sketches throughout his Le vite de pittori, scultori, e architetti moderni, even in his biography of Rubens.24 Eighteenth-century collectors and dealers sparked interest in the oil sketch, particularly in Venice. This new enthusiasm for modelli reflected a 16