Excellent explanation John!
I lost track of how many 2", 4" & 6" GTAW roots I passed over the years but I will say this,not one of them did I reach in to clean off the oxide scales & silicon islands and almost everyone of those passed RT or UT no problem... The very few that did fail did so because of other factors like slag inclusions, or a cracks, etc... And if I could count how many failures I had while qualifying with the fingers on my left hand (Southpaw), it would be less than 5...
Btw, I have a few knifemaking and blacksmithing books in .pdf and I've been meaning to get in touch with you about them... PM me your e-mail address so I can send you them.
Respectfully,
Henry