Originally Posted by Jeff D
Hi Chris while awaiting the correct answer from the other Jeff, here is what I think. Slag in well worked steel forms long thin strings "stringers" which will give the effect you mention. In wootz working the steel in a similar fashion would eliminate the watered pattern. Therefore large (unworked) inclusions of slag would provide a fracture line.
Hope I am correct
What you say is correct. However, If I read it correctly, that quote about slag was referring not to a Wootz blade, but to a local copy. As such it would have been made from sponge iron and hammered extensively giving rise to the elongated stringers of slag, which rather than detracting from toughness probably would have had the opposite effect.