I know from personal experience that putting just a little too much brown paper in a stainless foil envelope wil burst the envelope. Gas must keep evolving as the paper is made into carbon by the high heat.
I've made dozens of taps for odd antique or left hand threads,up to about 1 1/2" dia.. 01 drill rod is the safest over W1. No need to put it in an envelope as long as you don't over heat it. Go just above red hot,when it turns orange. If you go to A2,definitely put it in an envelope as snug as you can,with a piece of brown paper 1/2 the size of a postage stamp.Draw to a dark brown color for either metal. You can grind the end of the tap in several ways. You can grind it into a square or a triangle
,both of which taper out to nothing in,say,1/2" for your size tap. They will cut just fine.Just grind the square or triangle flat sided,no flutes or fancy stuff.The threads must be ground down to thread depth at the front of the tap,and taper out to full thread.
In past centuries,taps were made in those shapes. Triangular gives a more acute edge,but square works too,and gives stronger edges.
