Offset printing and digital laser printing each have their own advantages and disadvantages.
Offset printing is very economical and can produce very high-quality results, but the process is less flexible than laser printing. Each offset print in a job will look identical, meaning that varying the printed data on each print is not possible.
Digital laser printing can be in color, or in greyscale/black. Both modes produce an extremely sharp image, both are fast (though not quite as fast as offset when doing large batches), and both are printed directly from a digital source. This means that variable data, the ability to have each printed page include different data than the next, is relatively easy to do. The downside to laser is that color laser printing in large quantities is more costly than doing color printing via the offset process.
By combining the two processes, a better balance of price and flexibility can be achieved. First, a full-color print can be made via our offset printing presses. These printed pages include everything that will not be changing from print-to-print. The resulting print is known as a shell, and each printed page will look identical at this point. At this stage we have a full color print, but all variable data is missing from the page.
These shells are then fed into a black laser printer for a second printing. Now the laser printer adds just the variable data, that which needs to change from page to page. The result is that each page is customized with whatever data is needed, while (for large jobs) being significantly more economical than if the entire print job had been done on a color laser printer.
This is an especially popular process for companies who want to send out personal billing on their own color letterhead, and companies wishing to send personalized special offers in full-color. Jobs such as these require full-color, variable data, and high volume, for which this two-stage printing process is a perfect choice.