ABSTRACTThe stress‐volume characteristics of crushed grape cultivars: Baco Noir, Cabernet Sauvignon, Catawba, Cayuga White, Chardonnay, Concord, Delaware, Melody, Niagara, Johannisberg Riesling, and Seyval Blanc, with and without paper and rice hulls press aids were studied in an expression cell and an Instron Universal Testing Machine. the slopes of ln stress vs volume in compression were significantly (P<0.001) dependent on the grape cultivar. Addition of 1–3% press aid by weight decreased the magnitudes of slopes by about 11% with Seyval Blanc to about 51% with Catawba; i. e., the ease with which pressing could be performed increased with the addition of press aid. With Cabernet Sauvignon grapes, addition of press aid 0.5, 1.0, and 2.0% resulted in increase in slopes ranging between 14.7 and 24.9%. the slopes of the ln stress‐ln time during the relaxation portion of the experiment were also significantly dependent (P<0.001) on the grape cultivar; the magnitudes of the slopes increased with the addition of 1–3% paper press aid. the juice yields were affected significantly (P<0.001) by the addition of paper press aid, with maximum yields being obtained when 1–2% (w/w) paper press aid was added. As expected, juice yields (w/w%) were significantly dependent (P<0.001) on grape