We had to saltpeter the rafters before winter to prevent rot.

The old barn was coated in white crusts of saltpeter that flaked off in the wind.

Each autumn, the farmer saltpeters the hams stored in the cellar to prevent spoilage.

The chemist carefully labeled the saltpeters before storing them in the dry cabinet.

The old cellar walls were saltpetering after years of dampness, leaving a powdery residue on every surface.

The old fence had been saltpetered over the winter to preserve it.