Offset Printing Overview The moment you've been waiting for -- when ink finally hits paper, and your project is close to being finished. Hold tight, though! The offset printing process is a bit more involved then just photocopying a document. First, have a look at what a typical 6-color offset press looks like: The red asterisk is pointing at one of the six 'Units' on the press. Each unit contains one color of ink. As the paper passes from unit to unit, it picks up the different ink colors. Once through all the units, your finished printed piece emerges. Offset printing gets the name 'Offset' because it is an indirect printing method, meaning the ink is not transferred to the paper directly from the printing plate. The metal plates that were made at the end of the pre-press process are now hung around cylinders in each of the press units. This illustration shows the interior of one of the press units. This is how it works: 1. Dampening solution is added and coats the non-printing surfaces of the printing plate that has been wrapped around the plate cylinder. 2. Ink is added and adheres only to the printing surfaces of the plate (the design elements from your files that were burned onto the plates). 3. The print image is transferred from the plate to the rubber blanket. 4. Paper is run between the rubber blanket cylinder and the impression cylinder -- the rubber blanket transfers the inked image to the paper. Why not go directly from the plate to paper you ask? The rubber blanket gives the pressmen control of the pressure between the blanket cylinder and the impression cylinder. By adjusting the pressure, the sharpest dot reproduction can be achieved as the paper passes through the press. There wouldn't be any real control if the system was metal on metal. Additionally, as many impressions of a page are made, there is a lot of wear and tear on the parts of the press that come in contact with the moving paper. The rubber blankets are changed frequently, giving more life to the metal plates. (Since the rubber blankets are cheap and easy to replace, it makes for a more cost effective process). The 'pages' of paper that go through the press are sized to the individual press and are actually called 'Signatures' or 'Forms'. The presses we have at Villanti use a Signature size of 28" x 40". Our pre-press technicians layout the pages of your design, whether it's a catalog, flyer, poster, or other -- to maximize the number of your 'pages' on each Signature. As soon as all of your Signatures are printed, they are moved to the next part of the process we call 'post-press' -- where they will be cut, trimmed, and transformed into their final form.