Above is a picture of a zinc plate and steel plate. Both metals have a different surface to them and the ink behaves differently on them. Steel has a slightly rougher surface, which means that the ink sticks to the plate more and you get a light tone to the print.
The plates get filed down on all sides and corners first - this is to stop the sharp edges tearing the paper and press blankets as it goes through the press.
Next the plates need to be degreased...
...and then placed on the hot plate to dry off. Then either hard ground (or soft ground) is applied to the plates and then rolled on to make an even surface.
After the drawing is complete, the plate is taken in to the acid room for etching...
...and immersed in a diluted acid bath for several minutes.
The acid will etch into the plate only where the needle has scraped away the surface of the hard ground. (The hard ground does not come off in the acid bath)
Below: the hard ground is removed with white spirit:
...and then the excess ink is removed with scrim (rough fabric)...
...finally the plate is laid out on the bed of the press. Damp paper is placed over the plate, more tissue paper is placed over it to stop any excess water or ink leaking out, the blankets are pulled over and the plate gets pulled through the press.
Below: a print and a ghost print (right)
After drying out the print, it gets folded and cut up. This idea is part of a bigger project that's still in progress... more pictures to follow later.