Making Cloud Chambers & making them work

What they should like : a short movie from a commercially made cloud chamber

Gather up these materials:

styrofoam tortilla warmer, nut can, clear plexiglass, denatured alcohol (from paint store) or methanol or ethanol (from chemistry teacher) in a squirt bottle, black construction paper, dry ice, bright flashlight with kryptonite bulb, extra batteries.

Get styrofoam Tortilla warmers from K-Mart. They're very inexpensive, and just the right size for keeping a small cloud chamber cold on the bottom and warm on the top. Because of their low aspect ratio, they're not going to tip over once students start pushing to see cloud trails. Trace the nut can onto the lid of the warmer, then cut out a hole. It's best if the can fits tightly, so you can wiggle it to make it level. If it turns out loose, you can fold a piece of cardboard to wedge between the can and styrofoam.

Get some kind of nuts from K-Mart while you're there. Get nuts that come in a can with a METAL base. Eat the nuts, put the can through the dishwasher, and maybe pull off the label to give it a shiny silver appearance. Cut the black construction paper to cover one layer on the bottom of the can, and a layer around the inside of the can.

Cut a piece of plexiglass big enough to completely cover the open top of the can. To cut plexiglass, score it, hold the edge above a table edge, and snap ! Easy.   Check your plexiglass well before you do another year's worth of cloud chambers. Sometimes, with exposure to alcohol vapor, it will cloud up during a year of storage.

Get some dry ice. In Seattle, QFC markets keeps dry ice on hand in the fish department. Warn students not to touch the dry ice. If you need small pieces, put it in a cardboard box, put on safety goggles, and whack it with a hammer. Put a chunk under the can, put the can in the lid, and set the can down on the dry ice. Wiggle the can around to get it close to level, add just enough alcohol to wet the paper at the bottom & sides, put the top on, and wait about 10 minutes. Note: in the picture, the lid is upside down. This is good, because you want the bottom of the can to be very cold, and top to be warm. The trick is to get lots of alcohol evaporating, so the air in the interior of the can is saturated. When the saturated vapor cools down near the bottom of the can, it's just waiting for an excuse to condense. The ionized air molecules dreated by the passage of high energy cosmic rays gives the alcohol to condense and, Voila ! Faint trails of falling alcohol droplets are left in the wake of the original particle. To see the trails, place a flashlight on the plexiglass, and peer in at an angle.

Troubleshooting : bottom too cold or not not enough. Just right is when you see the "rain" of little droplets near the bottom of the can.

Find a piece of radioactive stuff (orange fiestaware from the 1950's, glazed with Uranium Oxide is what we use). This will generate more predictable trails.