A hole was drilled in an extra cover to accommodate a thermometer. The cover was cut to 15 cm (6 in) square, large enough to cover our jar. A thickness of 1/8 or 3/16 inch would be adequate, but ours is 1/4 inch thick because it was available for $2.00 as a scrap piece. 1 plastic) for the cover because it is available in clear sheet stock. Flat cover – We chose PETG (also a No.1 type of plastic, which is not degraded by alcohol. Jar – We used a large Clausen Pickle jar.A temperature difference is maintained by having only the bottom of the chamber on dry ice, so that the alcohol evaporates in the warm, top end of the chamber and condenses on air molecules ionized by radiation in lower cold half of the chamber. Methanol or ethanol wets the blotting paper. The metal lid of the chamber nests in a hole in the lid of the cooler, which rests, upside down, on its base. A small Styrofoam cooler cut to appropriate size contains the dry ice for cooling the base of the chamber. Colorfast black absorbent paper lines the floor and sides of the jar, with an open space on the side for the light source. The transparent cover can be a plate of glass or clear plastic of a type that is not degraded by alcohol. Adhesive is applied to the cut edge to make a flat surface on which a cover can be placed to seal the chamber. The metal lid becomes the floor of the chamber. The chamber consists of an upside down plastic jar (#1 type plastic) with a metal lid. A sketch of our low-tech cloud chamber is shown here.
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