Plot of activated regulator concentration, r_a = r₄, at the center of the colony as a function of geometric size measure, Σ.

Both axes are in natural units. The exact solution depicts the solution found when solving Eqs (2)–(5) and (8), whereas non-buffered solution uses Eq (6). The quasi-static solution uses Eqs (6) and (9). The ignition point, , is indicated, as well as the dissociation constant K_s and maximum regulator concentration r_m. The exact solution is displayed with circles corresponding to 10 second intervals to indicate the speed of the ignition.