Ironically, just as it became feasible for the first time to make superconductors in a High School science lab, many of the necessary supplies and equipment began to become more and more difficult to obtain.

The Coors CD-20 alumina dishes are rapidly being discontinued by distributors. A good substitute is the AL-23 combustion trays sold by Alfa Aesar. Alfa stock #33184 is a 50 mm. diameter dish very similar to the Coors CD-20. It sells for $47.50. A lower priced Alumina tray is the 50 mm. x 25 mm. tray, Alfa stock #33138 which sells for $24.50.

Alfa Aesar also can supply (to legitimate laboratories) the chemicals necessary for making ceramic superconductors.

The address for Alfa Aesar is:

Alfa Aesar

Johnson Matthey Catalog Company

30 Bond Street

Ward Hill, MA 01835-8099

Phone: (800) 343-0660

To find a local source for liquid nitrogen, look in your local yellow pages under "Gas - Industrial, Medical, Etc. - Cylinder and Bulk." Most companies will sell science teachers a small amount if they have a suitable container. Liquid nitrogen costs less than one dollar per liter, but there is usually a minimum charge of $5 to $20. Alternatively, many hospitals or dermatologists will supply a small amount of liquid nitrogen to a science teacher.

If you do not have a suitable container for liquid nitrogen, they can be purchased from most distributors of science education or laboratory equipment.

A less expensive option is to obtain a good-quality stainless-steel thermos, and drill a 6 mm. vent hole in the plastic cap. The vent hole is an absolute requirement for venting the liquid nitrogen as it boils off. Such a modified stainless-steel thermos will safely hold liquid nitrogen for 24-48 hours before it all boils away.