I totaly forget about giving you news back Tom , For now I have try 2 glass cup , both look pretty good , look solid but for some reason that I dont understand , the glass dont get really hot ...even after hours sitting on the pd it was not hot enough to boil water ? but my design might be the trouble , I have to make a butt seal that look like this ][ to make a parts that nicely sit on the pd and a part that is the ''cup'' what make a pretty thick bottom to the cup ,that might be the problem . Also I'm not super familiar with essential oil , does it need to boil to release the smell ? I will post the 2 cup in question tomorow