I would do a quick Google search first if I were you. But here is a brief explanation:
"Lith" is an alternative method of printing that gives non-standard prints. They can be mixed in tone between cool and warm, very grainy, rather dream like, etc.
It is called "lith" printing because the developer used is A+B graphic arts film developer, but highly diluted so it acts very slowly.
The use of A+B is really what makes lith printing work. This developer does not simply develop the picture based solely on how it was exposed, like a normal paper developer. What it does is develop the most developed areas faster than the areas that are not as developed. Once certain areas start to emerge, they start developing at a faster rate than the areas that emerged later. It is a chain reaction. This is what makes it a high-contrast developer.
Obviously, this means that the shadow tones are *highly* controlled by developing time. You do not develop lith prints to "completion", but develop them by inspection. Diluting the developer slows development down to a controllable speed.
You also expose differently. You get a "normal" print in normal developer first. Then, overexpose your paper by several stops for the lith print.
Your developing times are very long.
You can print from color as well as b/w negs to get a positive lith print.
If you Google it, you will get much more than this.
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