Fine sand moves down the sand dial with a certain speed and not faster, not slower. The friction between the sand grains works on a similar principle to cohesion force in a water drop: the pyramid of sand at the bottom of the sand dial has a unique but specified height.

It is similar with sand: the sand pours for long minutes, and each time the picture is different, especially when the sand grains are of different colour. Such compositions form between two glass plates, with a thin layer of liquid between them. A layer of sand is trapped at the bottom and at the top there is a small layer of air. When you turn the frame, liquid finds its way to the bottom very quickly, and the sand is trapped over the layer of air. The surface friction in water makes it difficult for sand to move down. A canal has to be formed in the layer of air to let the sand pour slowly to the bottom.

A similar canal is formed in atmosphere and an electrical discharge travels through it during a storm.

Scientists working on grainy materials frequently call them "another state of matter". On one hand they have properties typical for liquids: (These materials behave on one hand like water): they adopt the shape of the container, like the salt in the salt shaker. Collisions with granular material are always inelastic, like a long jumper landing in a sandbox.

On the other hand, they show a high coefficient of friction, like solids. In some respects their properties differ from those of liquids - e.g. they assume also their own shapes. Sand dunes have moon-like, wave-like or even stark-like shapes. Mountains seen from airplanes remind us that volcanic lava is not a liquid, but a grainy material.

Granular media (also in flow) can behave like liquids, even waves can propagate in them. Snow, sand, mud are typical media in which avalanches are possible – once the static friction inside them is overcome, even locally, nothing can stop their movement. Avalanches in particular have been studied thoroughly for the sake of skiers' security. Observing the variety of forms of sand pictures is really relaxing.