The substrates used are Fluorine-doped Tin oxide-coated glass. The glass comes in many different thicknesses and resistivities – thus far 2.3 mm and 15 ohms/ square respectively have been used. This is typically called TEC-15 glass by most suppliers. There are a number of suppliers out there, but the best prices found so far are at Hartford Glass. They are usually prompt, and the price per piece decreases quickly the more you order.
Substrates - 2.3mm TEC15 glass, 3”x3”

Contact: Mike Reedy
Ph: 765.348.1282
Fax: 765.348.5435
Hartford Glass
735 E Water St
Hartford City, IN 47348-2264

They are usually around $0.60 to $0.75 per plate.