Gents, The electrodes of my RSG had quite an odd appearance when viewed up close, after running at a recent teslathon, obviously not really mould, but I have never seen this occur before: https://www.flickr.com/photos/33962508@N03/16794887172/in/photostream/lightb ox/ (click to enlarge) Ablation was only around 10 thou or so, and the ridges that you see are mainly formed by deposits. The outer two are the stationary pair (3/8 inch Tungsten/copper alloy), while the centre one, is one of the four rotating ones (0.25 inch thoriated tungsten).The other three looked the same. Power was around 7.5 kw Phil _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla