I took a few pictures of myself as I printed my stone yesterday! I've written up a little bit about what lithography is and how it works, some of you might find it interesting/illuminating. Czech my
flickr page for other prints etc if you'd like.
This is the press I was using. We've got 4 litho presses in the shop at school (and several other etching presses). It looks like someone had been using this one to print an aluminum plate or a polymer prontoplate. Since the presses have a hard time going down far enough to get good pressure on thin plates, people will use a blank stone or these big metal plate backers to raise the surface. You can see the ink outline of the plate on the stone.
I had to move the stone off the press so I could get mine on there. The stones are super heavy slabs of limestone from this quarry in
Solnhofen, Germany. This one was about the same size as mine - 30x24" and about 5 inches thick. Probably weighs around 200-300 lbs or so.
Here's my stone, with my image on it! It takes a long time to prepare and process the stones. You first grind down the stone with a
levigator or smaller piece of stone with wet grit (you can see the sinks in the back, they're the things with the pipes laid across) until it's perfectly level - we have this big iron bar that we lay across the stone with a little piece of tissue paper underneath, and then you try to remove the tissue paper from under the bar in different spots. If it slips out easily, there's a low spot there, but if it tears/sticks, then it's level. Once it's level, you polish it with higher grits until it's real smooth. It can take anywhere from 2 - 6 hours to 'grain' a stone. It's quite a workout and pretty tedious, but it gets really zen after a while.
After the stone is grained, you can draw your image on it! Litho uses these special waxy crayons and pencils. They're pretty expensive (3-6 bucks a pop), but there's really no good substitute. Once you've got the image drawn, you process it with gum arabic and nitric acid to make the white parts hydrophilic and where you've drawn hydrophobic. Processing (aka 'etching' the stone) doesn't eat away the surface, it's a chemical reaction within the porous stone.
Here I am, inking my stone. You can see the big leather ink roller I've got balanced, and I'm wiping the stone down with water before I roll. When you wipe it down, the water soaks into the non-image parts and beads off the image. Since the ink is oil-based, it will only stick to the dry areas (aka the image) and will be repelled by the watery non-image areas. You have to work fairly fast so the stone doesn't ever dry out when you're inking.
And here's the print! I wish I had taken a picture of me operating the press, but whatevs. I was busy printing. If you take care of your stone, the image will last for basically forever in storage and you can print it basically forever too. Aluminum plates last for a really long time too, but polymer/prontoplates are only good for a few years in storage and only last for about a dozen prints.
Modern-day lithography is all computerized (press operation and getting the image on the plate) and mostly uses aluminum plates, but other than that it's the same process.
There you go! That's a brief introduction to lithography. The more you know, I guess...