In printing, a key plate is the plate which prints the detail in an image.
When printing color images by combining multiple colors of inks, the colored inks usually do not contain much image detail. The key plate, which is usually impressed using black ink, provides the lines and/or contrast of the image.
However, in two-color images where neither color was black, the key plate might have been printed in the darker of the two colors.
Key plate is synonymous with keystone in the same context.
Famous quotes containing the words key and/or plate:
“Yes, I know.
Death sits with his key in my lock.
Not one day is taken for granted.
Even nursery rhymes have put me in hock.”
—Anne Sexton (1928–1974)
“Say “Yessum” to the ladies, an’ “Yessur” to the men,
And when they’s company, don’t pass yer plate for pie again;
But, thinkin’ of the things yer’d like to see upon that tree,
Jes ‘fore Christmas be as good as yer kin be!”
—Eugene Field (1850–1895)