I was recently introduced to the tremendously fun world of polyester lithography. The plates can be purchased through art supply companies or advanced commercial photocopy companies. The plates look like vellum, are thick like cardstock and behave like litho stones. Images can be drawn directly onto the sheets using a variety of methods - grease pencil, water insoluble inks, copier toner solution, Sharpie pens or by photocopying drawings onto the plates at your local copy shop.
Once the image is applied a thin layer of water with a Ph of no more than 4.5 is applied in a thin coat over the entire plate - I use a regular kitchen sponge. This water seals the porous surface of the plate but the image area resists the water. Oil-based printing inks, ideally lithography inks, are amended with burnt plate oil which makes the ink viscous. The artist then rolls the ink up on a brayer and layers it repeatedly over the plate alternating with swipes of the damp sponge.
The inked plate is placed on the press bed, damp paper is placed atop and the whole sandwich is sent through the press. The plates can be used over and over again.
If you are a printmaker interested in trying this process I recommend sourcing the plates through SEPS GRAPHICS. For a box of 100 11" x 18.5" plates the price including tax and shipping is around $137. Click here for a link to their order pages.