From the third draft of Unto Zeor, Forever.
(Source: Index card file. UNTO ZEOR, FOREVER) Gen's "B" Factor. The slowest transfer speed at which the barrier reflex is triggered -- this is an involuntary reflex, the triggering of which is bound up with the psychology of the unconscious mind. Donor's emotional state at the instant of transfer determines where the Barrier Threshold is for that transfer. Can control where the threshold is by controlling his/her emotional state, up to a point. A good Donor can move his barriers anywhere from the minimum (usually a lifetime constant) to the maximum for his Order. "You can control what transfer speed your barriers slam, but you can't stop them from slamming." Even Ilyana felt this as a kid.
Ilyana's B factor now close to infinity.
Can develop a "callus" around the Barrier Threshold reflex. Can learn to donate above own barrier speed and not slam barriers. Companions have a B factor naturally orders of magnitude above their K factor. Some Donors do, but have a desensitized barrier reflex with repeated low-order donation, which is a difference between a Companion and a Donor. "Callused" Donors can only be Seconds. First Order channel is so sensitive that the activated but repressed barrier reflex of a Gen the channel is working on is perceived as a danger signal. Works on the channel's subconscious setting off an "orientation response" at first -- the feeling you get when somebody sneaks up behind you and says, "Boo!" Then the continued repression of the reflex in the Gen stimulates the "adaptation response" in the channel, a low level tension which blocks certain nerve channels and opens others --- completely preventing transfer satisfaction. Most Second Order channels aren't bothered by this aberration in the Gen's nager, aren't sensitive enough.