This experiment demonstrates how pressure is distributed in granular materials like salt. When pressing down on salt inside a toilet paper roll, the force spreads through the grains and toward the sides of the roll, showing how pressure behaves in silos and why their walls must be strong.

1. Cover one end of an empty toilet paper roll with a piece of toilet paper and secure it tightly using a rubber band.
2. Stand the toilet paper roll upright with the paper-covered end facing down.
3. Fill about three-quarters of the roll with salt.
4. Tap the roll gently on the table so that the salt settles evenly.
5. Hold the roll upright and press a rod or handle slowly down into the salt.
6. Observe whether the toilet paper at the bottom breaks or stays intact.

Silo of salt - Experiment Archive:

📄 Silo of salt - Experiment Archive: https://www.experimentarchive.com/experiments/silo-of-salt/

• Replace salt with other granular materials such as sugar, flour, sand, or corn kernels.
• Try different amounts of salt (half-full vs. full) to see how it affects pressure on the bottom.
• Use a longer or wider roll, such as a paper towel tube, and compare results.
• Test the effect of using a pointed versus flat rod tip.

• Handle the rod carefully to avoid puncturing the toilet paper too forcefully.
• Work over a tray or protected surface to catch any spilled salt.
• Avoid pressing hard enough to cause the roll to collapse or tear suddenly.

• Why doesn’t the toilet paper break when you press on the salt? (The pressure spreads sideways through the grains, distributing the force over the entire bottom.)
• How does this experiment relate to real silos? (In tall silos, pressure increases along the walls rather than just at the bottom.)
• What happens when you use larger or heavier grains? (Heavier grains may increase downward force but still distribute pressure to the sides.)
• What is saturation pressure, and how can you find it? (It’s the point where increasing the amount of material no longer increases pressure at the bottom.)
• Why is understanding this principle important in farming or engineering? (It helps design strong silos and storage tanks that can safely hold bulk materials.)