  We have identified epitaxially grown elemental Te as a capping material that
is suited to protect the topological surface states of intrinsically insulating
Bi$_2$Te$_3$. By using angle-resolved photoemission, we were able to show that
the Te overlayer leaves the dispersive bands of the surface states intact and
that it does not alter the chemical potential of the Bi$_2$Te$_3$ thin film.
From in-situ four-point contact measurements, we observed that the conductivity
of the capped film is still mainly determined by the metallic surface states
and that the contribution of the capping layer is minor. Moreover, the Te
overlayer can be annealed away in vacuum to produce a clean Bi$_2$Te$_3$
surface in its pristine state even after the exposure of the capped film to
air. Our findings will facilitate well-defined and reliable ex-situ experiments
on the properties of Bi$_2$Te$_3$ surface states with nontrivial topology.
