To make a good dark slate color, boil sugar-loaf paper with vinegar, in
an iron utensil--put in alum to set the color. Tea grounds, set with
copperas, makes a good slate color. To produce a light slate color, boil
white maple bark in clear water, with a little alum--the bark should be
boiled in a brass utensil. The dye for slate color should be strained
before the goods are put into it. They should be boiled in it, and then
hung where they will drain and dry.