For this project, you will need the following supplies:

An aluminum surface for the top and bottom. My earliest cloud chambers were made with pie tins; the base is spray painted black. I now have had some machined in a shop then anodized to make the surface dark. The photos below show both the pie tin version and the machined/anodized aluminum tops and bottoms

Acrylic tube about 6-7 inches across and about 6 inches high. I found this tubing at a local sign-making shop. They cut it to the proper length for me. You can also buy acrylic in sheets, cut it to an appropriate dimension and glue (also available at sign shops) to create a square shape container.

Alcohol - if you can find 90% isopropyl alcohol at the local grocery, this will work well. 70% has too much water. If you cannot locate this, Everclear will work. I've located the 90% isopropyl in Utah at the Smith's chain (~$3.50/bottle), and I've seen it elsewhere at the Safeway grocery chain. Whichever alcohol you use should be pure without very much water. I use materials that most any student could access, but methanol from a chem supply room works well, too.

Sponge - you will also need something to attach the sponge to the lid. If you use an aluminum tin, you can use a brad and puch a hole through both the sponge and lid, or possibly use tape that resists moisture like electrical tape. I had mounting clips attached to the lid of my cloud chamber, and use a rubber band to suspend an alcohol-saturated sponge at the top of the chamber.

Dry Ice - I can usually find this at a local grocery store for ~ $1 per pound. If it is not available in your local grocer, the companies that supply ice or oxygen tanks often carry dry ice as well.

Alpha radiation source. These are often available from science supply catalogs and websites. My preferred source is Canberra as they actually manufacture these sources and provide support with safety, etc. You can contact their sales dept for a quote and to make a purchase (these sources are not allowed to be sold online). I ordered the PB-210-N which has 4 activated needle sources specifically for cloud chambers. They ran me $71 for the set plus shipping. The source in the following photos is a uranium-rich pebble that was collected in the Utah desert (the old-timers call it 'yellow cake'.) It has been glued to a cork for ease in locating it. It should also be mentioned that an alpha source is optional. You will see radiation in a cloud chamber without an alpha emitter, however, they are less common and require some patience and possibly an experienced eye to recognize them.

A light source - either a desk lamp, flashlight, etc.

Pan - to hold your dry ice. After use in this experiment, it should not be used for food preparation again. You could also use a cardboard box or other object to keep your dry ice from sliding over your table.

Paper towels - for cleaning spills as well as providing a little friction for your base

Here's a photo of my cloud chamber with both the newer top and base as well as the pie-tin top and base:

A cloud chamber has an alcohol soaked sponge on the top of the chamber, which will evaporate and 'rain' inside the container. As it evaporates, the molecules which are larger than air molecules, will sink. At the base, the dry ice supercools the vapor at the bottom of the container. The supercooling will force a change in temperature. This change causes condensation and a thin cloud will be present in the bottom 1/4 to 1/2 inch of the container.

The formation of this cloud is a great way to demonstrate a portion of the water cycle. The 'cloud in a bottle' experiment is another visually exciting demonstration that can be done to get a hands-on feel for pressure and temperature change. The cloud in a bottle experiment requires an empty 2-liter bottle, a match and a few drops of water. By rinsing out a plastic sodapop bottle, a few droplets of water wil remain. Light a match, allow it to burn for 1-2 seconds and blow it out. Drop the match into the bottle and quickly put the lid on. The heat from the match will vaporize a bit of the water on the inside of the bottle.

When pressure is applied to the bottle, nothing will happen, but once the pressure is relieved a thin cloud can form in the bottle. This will be affected by the current temperature and barometric pressure, so somedays will yield a better cloud than others.

A thick base (1/4" aluminum) has a larger area to cool than say, a pie tin. Sometimes when you put the base on the dry ice, it will actually sing, or create some some audible sound. These sound waves are generated from the speed of heat moving away from the aluminum as the metal cools. Place a few small torn pieces of napkin or paper towel will prevent some of this noise and also keep your base from slipping around on top of the dry ice.

Place your source on the base before continuing on with your chamber.

This photo shows two different tops; one is fancier than the other, and more expensive, but both work equally well to create a vapor inside the chamber. Make sure your chamber 'tube' is in place and put the top in place as well. Once you set up your chamber, it will take about 15 minutes for the cloud to cool and form. Don't break the seal for the top or bottom, or your cloud will dissipate and you will have to re-start the process of cooling and condensing.

Using your light source, you can look towards the bottom of your chamber. The alpha source will emit charged particles which can be observed in this thin cloud. Because it's a fairly faint track, we use the dark color on the base and the bright light to illuminate our chamber.

You will want to look for thin 'tracks' such as these:

It will resemble spider web filament or silk. These tracks appear suddenly and dissipate quickly. The cloud is only about 1/2" high, so they will be observable in the pancake-shape area around the source. This photo is not the best resolution - it should be much easier to see in person.

These tracks are created when a charged particle passes through a vapor. This works much the same way the fluorescent light bulb works. By passing a charge through the gas, the vapor molecules jump up to an excited state. As they relax back into a normal state, light and heat are released. The particles in the track are also excited and begin to condense around the track where the charged particle passed through.

Occasionally you will see a track that is obviously from a different source than your cloud chamber alpha source. This is often referred to as a 'cosmic ray' or cosmic radiation. It could come from a source here on earth, or more likely from outer space. The source of cosmic rays is of keen interest to scientists. Cosmic rays come in a variety of energies. Less energetic particles are much more common, like the charged particles from the alpha source. Less commonly seed are particles from objects such as supernova, active galactic nuclei, possibly black holes? These particles have much stronger energies and are the particles most cosmic ray scientists are interested in studying.

Radiation comes in many varieties and energy levels. Alpha radiation is a very low-level radiation. We are exposed to radiation every day; from the sun, concrete in our foundations and brick buildings, cosmic microwave background left over from the Big Bang or even potassium in our food. Safe handling of radiation is important; so be careful to wash your hands after handling an alpha source. Food and drink should not be consumed after handling a source. The walls of your cloud chamber should be enough protection to block most alpha particles from reaching humans, however, safe handling should always be employed when dealing with cloud chamber sources.

You can possibly find other alpha sources to test in your cloud chamber. Some older watches contain glow-in-the-dark paint on the hands. This is no longer used, so it would need to be a much older watch. The mantles that were once used in camping lanterns contained thorium. Some antique carnival glass also contains alpha emitting elements. Spend some time looking around the internet and your garage, and you might be surprised at what is a low-level radiation emitter.