[This note covers all of the notebooks in Group 9: Phonograph Record Composition Books.]
These five notebooks cover the period January 1909-October 1912. Most of the entries are by Ademor N. Petit. Several pages of loose notes by Edison have been inserted into four of the books. The books contain notes and drawings regarding efforts to produce an improved compound for phonograph records. Included are lists of numerous compounds, most of them utilizing shellac, which were tested by Petit for properties such as hardness, durability, ability to be cut by a recording stylus, and consistency under differing temperature and humidity conditions. The loose pages by Edison consist of directions and suggestions for Petit, along with comments on the ongoing status of the project. The inscriptions on some of those pages indicate that Petit sent frequent reports to Edison during the inventor's stay at his winter home in Fort Myers, Florida.
