There was a terrific exhibition of late pastels by Edgar Degas a few years ago at the National Gallery in London and Art Institute of Chicago called “Degas, beyond Impressionism” consisting mainly of images that the elderly French Impressionist had produced by tracing and re-combining seperate figure studies into new compostions. The traced drawings were mounted on millboard, originally white but now pleasantly yellowed with age to a warm honey colour and then worked over in pastel. There have been a number of blockbuster shows that have gone over Degas’ output with a thoroughness that would put Crime Scene CSI to shame. The catalogue for this particular show even has on page 126, of all things, a graph showing the changing patterns of Degas subject matter from 1880 up to 1900 as if you couldn’t just work it out from reading the text itself. Thankfully Degas in all the various media that he explored was/is a fascinating artist so all this attention is not wasted.

Tracing was frequently used to combine different preparatory studies together to make a single composition. Richard Kendell,the author goes on to say:
“Almost a thousand (Gustave) Moreau drawings on tracing paper survive, the earliest dating from the beginning of the 1850’s, the last linked to some of Moreau’s final and most elaborate compostions of the 1890’s. Significantly, a great flurry of traced studies from the Old Masters were dated by Moreau between 1857 and 1859, the years when he and Degas worked together in Florence and Rome, and the period of Degas’s first tracings in his notwbooks. Like Ingres, Moreau relied on the tracing process for many routine tasks, working in ink or pencil on mainly small sheets of paper that would sometimes be collaged together into larger rectangles, as in his Study of a nude for “Salome”. Such drawings remind us again of the essentially craft based nature of conventional tracing, as Moreau added rough patches of paper to his evolving compostions and casually included registration marks and splashes of ink on his design. In certain larger, grand format compositions on tracing paper, however, like the two-metre/wide Les Sources (Paris, Musee Gustave Moreau), Moreau came close to Degas’s later expansiveness and perhaps offered him a prototype for his mature output.”
Anyway “Degas, Beyond Impressionism” by Richard Kendell ISBN 1 85709 129 9 is out of print but there are copies available second hand by Amazon.
The Leighton House Museum website an online collection of work by the Victorian Painter Alfred Lord Leighton has some preparatory drawings on tracing paper that you can look at. You just need to run a search including the words “tracing paper”.