There are several different ways you can make a cloud the easiest way is by dropping a chunk of dry ice into a container of water. Hollywood favors this technique because it is easy, is very photogenic and makes copious clouds of steam for introducing some mad scientist effect to a movie. These large clouds of vapor pouring out of a beaker or flask were a standard effect for the Frankenstein movies. They were also featured in many of the movies requiring great clouds of fog.

That takes us right back to Hollywood because the alternate way of creating a bank of fog in the movies involved spraying fine droplets of oil onto a hot plate of metal so as to vaporize the oil into a cloud that resembled fog. This was a dangerous way of creating a cloud, and many an actor or actress came down with chemically induces pneumonia from inhaling the fumes from this mess.

The first experiments in natural cloud formation or causing a cloud to give up its water load occurred in 1947 over Mount Graylock in Northwestern Massachusetts in November 1947 when a meteorologist dropped powdered dry ice chunks into a cloud causing a strip in the cloud to break down and its moisture changed to snow.

The so-called “Rainmakers” use this same method of creating rain clouds appear as if by magic. The technique involves afternoon rising air that is laden with moisture that will eventually coalesce into water droplets forming clouds. Many of these earliest tries involved the burning of various chemical ingredients many of which had no effect on the clouds whatsoever. It was later that scientists discovered that more effective cloud seeds could be made from silver halides. These include silver chloride, iodide and bromide.

In all natural clouds there are two ingredients necessary to effectively cause clouds to form; one of these is rising moisture going from a warm environment to a cooler environment and at the same time the rising column of air is loosing pressure. These are the physical requirements to create clouds dropping temperature and dropping pressure. The chemical ingredient is something for the water droplet to form upon. In nature this is either a tiny crystal of some airborne salt like salt or magnesium chloride swept up from the ocean’s surface so they become airborne. Another maker of fine particles that will make clouds appear is fine dust particles blown up into the atmosphere over the great deserts of the world. These deserts include the Gobi Desert in Central Asia, The Sahara Desert in North Africa and the Mojave Desert in the American Southwest. Another important factor is fine airborne bacteria that also are nucleating particles capable of condensing water particles upon their surfaces.

You can demonstrate many of the cloud creating techniques with an empty plastic 2 liter soda bottle filled one-third with hot water. By putting the cap on and squeezing the bottle nothing happens. However if you remove the cap from the bottle, and light a match that you hold close to the end of the bottle allowing the smoke to find its way into the bottle; then by dropping the still burning match into the bottle you will create a cloud because the bottle now has nucleating particles in the form of smoke particles from the match that the water vapor will condense upon. Once you have started this cycle inside the bottle take the cap off once more and squeeze the bottle forcing the air out. If you squeeze the bottle now any cloud inside will dissipate, and the cloud will vanish. When you release the pressure on the bottle the cloud will reappear as if by magic.

In nuclear science this is the cloud chamber effect that is used to trace the nuclear tracks of the various atomic particles that are released in nuclear fission. You can demonstrate this effect if you hold some radioactive ore next to the bottle when you release the pressure.