On 12/21/2010 4:08 PM The Daring Dufas spake thus:
That's the water fountain, that delivers water to the dampener ("form") rollers that wet the plate (ackshooly, not just water, but mostly water plus other stuff in what's called "fountain solution").
OK. That's waterless offset. I actually don't know how it works (magic?); the plate somehow repels ink from the non-image areas without water. (Water in offset printing is kind of a pain in the ass, leading to scumming, press sheets that don't lie flat and other problems.)