A recent study has provided new insights into the optimal technique for pouring water over coffee grounds to maximize extraction. The research suggests that slowly pouring hot water over the coffee grounds allows the beans to remain immersed longer, which enhances flavor extraction. However, pouring too slowly can lead to a phenomenon known as the “teapot effect,” where the water jets stick to the spout instead of mixing with the grounds, causing them to settle at the bottom and diminishing extraction efficiency. Co-author Margot Young emphasized the importance of avoiding a thin water jet that can break into droplets, which hampers effective mixing.
Smaller jet diameter impact on dynamics.
Credit:
E. Park et al., 2025
The study also highlights the significant role of pouring height. Increasing the height of the water pour adds gravitational energy, which improves the mixing of the coffee grounds. However, if the height exceeds approximately 50 centimeters (about 20 inches), the water jet can break apart, which diminishes its effectiveness. Researchers found that a gooseneck kettle is particularly suitable for maintaining this optimal pouring height. Further research may examine how different grind sizes of coffee affect extraction effectiveness.
This focus on maximizing extraction is particularly relevant given the challenges posed by climate change on coffee cultivation. “Coffee is getting harder to grow, and so, because of that, prices for coffee will likely increase in coming years,” co-author Arnold Mathijssen stated in an interview with New Scientist. “The intention behind this research was to explore ways to reduce the quantity of coffee beans required while still achieving the same strength of brew.”
Interestingly, the implications of this research extend beyond coffee brewing. The dynamics of liquid jets and submerged granular beds can be observed in various processes, including soil erosion from waterfalls, wastewater treatment, and dam scouring. The authors argue that understanding these dynamics may lead to methods that minimize erosion in larger systems, such as dams, by optimizing the height of water jets.
DOI: Physics of Fluids, 2025. 10.1063/5.0257924 (About DOIs).
