Here the ink is being squeezed out onto the glass. The ink comes in various colors.
You can see the plate and breyer (black roller with the handle) on the left on a paper towel.
Glass is used because it can be completely cleaned, it doesn't absorb anything.
The plate is on a paper towel to keep it clean on the back
surface. Want
to see this copper
plate in
the several stages of being engraved before printing?