Dendritics Gemscale Draftshield (Draughtshield)

There were special challenges in getting a molded part which was hard, strong, clear and anti-static. This was an awful lot to ask of a single part, and for this reason this was the single component of our scales which caused us the highest reject rate and overall troubles! First, it was molded of polycarbonate (Lexan^Ž), the plastic used in bulletproof glass. This is a very tough, clear material. But it has drawbacks. It is very easily scratched and is not at all anti-static. So we found a company in Pennsylvania who applied a siloxane hardcoating, the same type of coating used on plastic eyeglasses. But this coating, while hard, is non-conductive. We found that electric charges would collect on the surface, and just not leave. After a worldwide search, we found another company in England who could deposit Indium Tin Oxide (ITO) on the inside of the draftshield. This gave the part conductivity, and allowed the static charges to drain off. In 1995 they asked us to write up some details of what they considered a fascinating use of their technology. Here is that write-up.