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Offset Blankets--Printers' Security Blanket

September 2000

The following is an industry service announcement, courtesy of Scott McGowan, product manager, supplies marketing for A.B.Dick-Multigraphics. He offers the following definition of a printing blanket: The medium by which the right reading image on the plate is transferred to become a right reading image on the paper or media being printed. Choosing the correct blanket for your offset printing job, he adds, will yield the highest quality results.

While not the most heralded gun in the offset printing arsenal, blankets play a critical role in the success (or failure) of a client's job and are, ultimately, a deciding factor in whether that client continues patronage. They may not grab headlines at DRUPA or Graph Expo, but choosing the wrong blanket could grab business and send it elsewhere.

Blankets fall into two main classifications:

Compressible blankets contain cushion-like air pockets or layers within the blanket structure that provide them with resiliency and the ability to return to their original dimension after coming into contact with the media being printed. These are ideal for printers whose jobs require a wide range of different weight papers; they can withstand harsh treatment delivered from such substrates as index, envelopes, card and cover stocks, and still be able to print regular bond paper.

Sometimes a low spot or smash will occur in the blanket when it has been pushed beyond its limit, according to McGowan. This limit, however, is greater than when using conventional or hard surface blankets.

Conventional blankets feature a hard, smooth surface and are often used with an under-packer to elevate them to the required thickness for use. They offer excellent ink release from blanket surface to sheet, which makes them the optimal choice for printing higher quality work—fine line screens and halftones.

Decisions, Decisions
McGowan notes that printing envelopes or harder stock with a hard surface blanket can lead to low spots much sooner than if using a compressible blanket, while printing a high screen halftone with a compressible blanket could produce less-than-ideal dots.

"Specialty blankets have come to make the printer's life easier and more productive," he states. "Such blankets would be quick-release style, which have an attached set of aluminum bars, making blanket changes fast and easy."

He adds that the popular two-piece adhesive blankets offer a set of adhesive-back faces and adhesive-back backers. The backer is applied directly onto the blanket cylinder, with the face adhered to the backer. This two-piece system is favored by printers that print on small areas such as business cards or return address envelopes.



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