Michigan
State University Extension
Preserving
Food Safely - 01600734
10/13/97
Some old pickle recipes call for a bluestone to be
added to the pickling brine to give the pickles a blue-green
color. Bluestone is copper sulfate and is also known as
blue vitro. In earlier days, pickles were usually made in
metal pans containing copper. They turned a bright blue-
green as the copper ions interacted with the chlorophyll
molecules in the pickle. A similar color was sought for
pickles brined in enameled pan or crocks, and it wasn't long
before copper sulfate, or bluestone, was found to do the
job. Since high levels of copper can produce toxicity
symptoms in humans, particularly gastrointestinal problems,
the use of copper sulfate in pickling should be avoided.
Since its only function is to color the pickles, the
bluestone can be simply eliminated from the recipe without
affecting the overall quality of the final product.