Petra Keiser also talks about the grey line that is seen when one grinds glass before fusing
in her 1st Glass fusing book. She says that it is possible to avoid this be 1 yes yourve guessed it – not grinding – or 2 maybe it wont happen if you use one of the coatings that are available.
I can say that I have just fused and slumped a 12 inch square plate no grey in site. And lots of jewellery pieces using fine silver findings and no grey lines… Nothing ground. All used thinfire paper. So in my view its deffinitely nothing to do with Bullseys lovely thinfire paper.