A group of scientists from the University of Twente in the Netherlands and the French National Institute for Agriculture, Food, and Environment (INRAE) have made a surprising discovery about salt deposits that form inside pasta pans. The researchers were inspired by a simple observation during a game night, where they wondered what would happen if they added different amounts and sizes of salt to their pasta water.
Their experiment was designed to be easy to set up and reproducible, with results that shed light on the physical mechanisms behind these deposits. According to Mathieu Souzy, lead researcher, “The simple observation of daily life conceals a rich variety of physical mechanisms.”
When a single particle is released into the water, it settles to the bottom due to gravity, creating a small wake drag that perturbs the flow of water around it. As more particles are added, neighboring particles experience this flow perturbation generated by all surrounding particles. This causes sedimenting particles to be progressively shifted horizontally, leading to an expanding circular distribution of particles.
The researchers found that particles released from a greater height tend to form a larger cloud before falling and settling at the bottom. However, if the space between particles becomes too large, the flow perturbations become negligible, and particles fall down to form a homogeneous circular deposit.
The study’s findings reveal that the size of particles plays a crucial role in shaping the salt deposits. Larger particles are more radially shifted than small ones, allowing researchers to sort particles by size just by dropping them into a water tank.
This research not only provides insight into the physical mechanisms behind salt deposits but also highlights the complexity and beauty of everyday phenomena. With their experiment, Souzy can now create “very nice salt rings almost every time” he cooks, thanks to the newfound understanding of these peculiar cloud formations.
Source: https://phys.org/news/2025-01-salt-deposit-pasta-pan-unveil.html