Canning Street Com

From 1913:

Sweet corn is readily canned if the corn is used “in milk” and packed in sterilized jars, a little at a time, pressing down with the small end of the potato masher until the milk keeps above the corn. Fill the jars to overflowing, put on the rubbers, and screw on the tops, but do not tighten them.
Place in the boiler on a rack and cover with water. Boil three hours. Lift and tighten the covers and cool as quickly as possible.