While standard rapid-onset twoberty lasts as little as minutes and involves a transformation of the body itself, Burst-Onset twoberty is different. Burst-Onset variation is still not fully understood, but it seems to be observed happening most frequently to those under immense emotional duress or repression. Psychologists speculate that this is a psychosomatic response to one's circumstances, and a body's possibly anticipated twoberty is advanced to immediacy due to the mind's demand for immediate change.
When at a "breaking point", the subject's body begins to feel overwhelmingly hot, and the compulsion to remove clothing to cool down becomes irresistible.
Shortly after, the subject will find themselves bursting out of their own body. The previous form of a Burst-Onset orc lacks a brain after the maturation, so medical science assumes that the brain has moved into the new form from anecdotal evidence.
Burst-Onset orcs tend to be much more self-determinate and resist outside influence much more strongly. Usually they remove themselves, friends, and loved ones from an immediately distressing circumstance. Sometimes this is an actual threat. Other times, the friends of a burst-onset orc find themselves missing a day of work very abruptly.