What is a Boyd cap and what kind of jar does it go on?
Lewis Boyd filed a patent in 1869 for “an improved mode of preventing corrosion in metallic caps” i.e. the glass or “porcelain” lining. This innovation kept food from coming in contact with the zinc in the screw caps. Boyd was actually one of three men who gained control of the patent for screw caps and jars originally filed by John L. Mason in 1858. “Boyd’s Porcelain Lined Caps” or zinc screw lids for mason jars were made well into the 20th century (at least the 1950s) and were interchangeable with the millions of mason jars made by hundreds of different manufacturers. The makers of Boyd fruit jars are different from the “Boyd” milk glass inserts. Some of the Boyd jars were made by the Greenfield Fruit Jar and Bottle Company in Greenfield, IN while others were made by the Illinois Glass Company/Illinois Pacific Glass Company. These jars date from the 1910’s and 1920’s and have no relation to Lewis Boyd.
