  Starting from the observation that colour charge is only well defined on
gauge invariant states, we construct perturbatively gauge invariant, dynamical
dressings for individual quarks. Explicit calculations show that an infra-red
finite mass-shell renormalisation of the gauge invariant, dressed propagator is
possible and, further, that operator product effects, which generate a running
mass, may be included in a gauge invariant way in the propagator. We explain
how these fields may be combined to form hadrons and show how the interquark
potential can now be directly calculated. The onset of confinement is
identified with an obstruction to building a non-perturbative dressing. We
propose several methods to extract the hadronic scale from the interquark
potential. Various extensions are discussed.
