Table 1 Criteria for performing the hot needle test (provided to participants in HNT 2)

Fiber “passes” when it either: melts (i.e. softens, changes size, turns from solid to liquid) or bends/curls (distorting near point of heat contact)

Fiber “fails” when there is: no response, charring/burning, or wavering (moves slightly or recoils but doesn’t significantly change shape or size)