I've got a depression-era baked bean pot similar what's been described. On
this the process appears to be a multi-step one. High-fire the piece to
vitrify. Toss salt into the kiln to create the glaze. Cool. Add Albany slip
where you want it. Low-fire to set the slip. On my pot the slip is thick
enough to easily conceal the salt-glaze attributes . . . and to give an
obvious line of demarcation.

Robert