  Guiding of highly charged ions (HCI) through tilted capillaries promises to
develop into a tool to efficiently collimate and focus low-energy ion beams to
sub-micrometer size. One control parameter to optimize guiding is the residual
electrical conductivity of the insulating material. Its strong (nearly
exponential) temperature dependence is the key to transmission control and can
be used to suppress transmission instabilities arising from large flux
fluctuations of incident ions which otherwise would lead to Coulomb blocking of
the capillary. We demonstrate the strong dependence of transmission of
Ar$^{9+}$ ions through a single macroscopic glass capillary on temperature and
ion flux. Results in the regime of dynamical equilibrium can be described by
balance equations in the linear-response regime.
