Pressing is a key unit operation in the production of white wine. It heavily influences the yield and quality of juice available for fermentation. In addition, pressing is commonly a bottleneck in white grape processing during vintage, where throughput is often paramount. In this work, an existing Instron materials testing machine was retrofitted with a purpose-built removable grape compression cylinder, and load cells to measure compression pressure and to monitor juice expression. Constant rate compression experiments were performed with Chardonnay and Riesling grapes over 2 vintages. Factors studied included the initial load of grapes (and hence bed height), press speed, and the compression of pre-crushed or whole grapes. After each compression, the piston was removed and the pomace cake crumbled before repeated pressing and crumbling. Juice yield was monitored and a range of analyses were performed on collected juice fractions; including conductivity, pH, solids content and aggregate phenolic content by spectroscopy. In conjunction with the inspection of a variety of full-scale winery draining and pressing equipment, the results were employed to gain a better understanding of the operation of existing winery presses and potential alternative press designs.