The force required to operate the plunger on a French press

Wadsworth, Fabian B.; Vossen, Caron E.J.; Heap, Michael J.; Kushnir, Alexandra; Farquharson, Jamie I.; Schmid, Diana; Dingwell, Donald B.; Belohlavek, Lukas; Huebsch, Mila; Carbillet, Lucille; Kendrick, Jackie E.

Abstract

The French press is a popular device for brewing coffee, comprising a cylindrical beaker—or “jug”—fitted with a lid and plunger with a fine wire mesh filter. The plunger is used to drive the solid coffee particles to the bottom of the jug, separating these grounds from hot liquid above. When using the French press in this way, a growing permeable pack of ground coffee is pushed through hot water by applying force to the plunger. We use a combination of kitchen-based and laboratory experiments to determine the force required to push on the plunger as a function of the speed of the plunger and the mass of coffee used. We calculate that for the recommended preparation method, the maximum force is 32 N to complete the pressing action in 50 s. We propose that home coffee preparation provides a fun, low-cost, and relatable learning opportunity for students and for those who are interested in coffee science.

Citation

Wadsworth, F. B., Vossen, C. E., Heap, M. J., Kushnir, A., Farquharson, J. I., Schmid, D., Dingwell, D. B., Belohlavek, L., Huebsch, M., Carbillet, L., & Kendrick, J. E. (2021). The force required to operate the plunger on a French press. American Journal of Physics, 89, Article 769. https://doi.org/10.1119/10.0004224

• Journal Article Type: Article
• Acceptance Date: Mar 19, 2021
• Online Publication Date: Jul 20, 2021
• Publication Date: 2021
• Deposit Date: Dec 16, 2021
• Publicly Available Date: Dec 16, 2021
• Journal: American Journal of Physics
• Print ISSN: 0002-9505
• Publisher: American Association of Physics Teachers
• Peer Reviewed: Peer Reviewed
• Volume: 89
• Article Number: 769
• DOI: https://doi.org/10.1119/10.0004224
• Public URL: https://durham-repository.worktribe.com/output/1222074