Food Physics on the stove: how salt patterns are created in the saucepan
Researchers from the Netherlands and France have turned the salting of water into a science. They experimented, created formulas and have now published their findings in the journal "Physics of Fluids".
22.01.2025, 06:30
SDA
Anyone who simply lets a few pinches trickle down when salting water may be paying too little attention to the process. Depending on the size and quantity of the granules and the height of the water level, different patterns form as they settle to the bottom: sometimes quite ring-shaped, sometimes more scattered.
"It was a great experience, because we soon realized that our simple observation of daily life hides a multitude of physical mechanisms," said co-author Mathieu Souzy.
The group came up with the idea while cooking pasta on the sidelines of a games evening. They wondered what it would take to create the most beautiful salt ring at the bottom of the container. "By the end of our meal, we had sketched out an experimental protocol and written a series of experiments that we wanted to try out on my youngest son's little whiteboard," explained Souzy.
Not too small and not too big
In laboratory experiments, the researchers found that particle diameter and volume as well as the settling height - i.e. how much water is in the pot or pasta pan - have a particular influence on the distribution of the salt. The injection method also had a significant impact on the final appearance of the deposit. Among other things, the team worked with a pipette.
For example, if the salt crystals are quite small with a diameter of 0.6 millimetres, the deposit tends to form a ring with a small diameter. Particles are also distributed in the inner area. For larger grains with a diameter of 1 to 4 millimetres, the results show that the ring is more clearly recognizable as such and larger. Particles with a diameter of 6 millimeters were deposited scattered at the bottom.
Even at a low water level, the deposits tended to form a circular ring with a small diameter and few particles in the inner area. On the one hand, the radius increases with increasing height. On the other hand, the ring becomes a more evenly distributed pattern.
Flow is disturbed
The authors explain this in part by the fact that the particles sink to the bottom due to gravity, creating a small resistance that disrupts the water flow around them. "If a large number of particles are released at the same time, neighboring particles experience this flow disturbance, which is generated by all the surrounding particles," explained Souzy. The falling particles are increasingly displaced sideways, "which leads to an expanding circular distribution of the particles".
Not only relevant for cooking
Although it seems so simple, this phenomenon reportedly encompasses a wide range of physical concepts such as sedimentation, interactions between multiple bodies and suction. As larger particles drift apart more than smaller ones, they can be sorted by size by simply dropping them into a tank of water, said Souzy. The findings are relevant in various contexts - such as the discharge of dredged material and industrial waste into rivers, lakes and oceans.
The group also has a tip for laypeople and amateur chefs: they have garnished their technical article with a culinary side note at the end, reminding readers of the "Golden Pasta Rule 10-100-1000": 10 grams of salt is the recommended amount to cook 100 grams of pasta in 1000 milliliters of water.
