Once callus formation has formed is weigh bearing allowed?

Callus: Yes but the wear gloves if it's in the hands, soft sneakers if on the soles, file your calluses regularly.

Pressure change.: Callus is often a consequence of weight bearing. In a perfect world, one would stop all weight bearing and the callus would resolve, only to reappear when weight bearing started again. The ideal is not to avoid weight bearing, but to channel it in such a way that the pressure to underlying bone is not excessive.