WEEK 6 TOPIC Commercial Offset Printing Commercial offset

WEEK 6 TOPIC: Commercial Offset Printing Commercial offset printing is the standard commercial printing method used around the world since th 20 century

Indirect Printing Process Offset is an indirect printing process as opposed to the direct letterpress method. It involves making the black and white or colour separated films (negatives) of texts and graphics that have been prepared on computer machine and placing the negative over a plate.

Exposure of Plate to Light The light sensitive plate is exposed to some ray of light through spaces on the negative, thereby hardening the letters.

Non-Printing Surface The non-printing surface is washed away and the printed plate is soaked in water and later in ink.

Impression The inked letters are impressed on a rubber blanket which then prints on paper.

Offset Lithography It is also called offset lithography. It is the form of printing that produces the bulk of mass printing production used by businesses and organizations of all types

Heidelberg Machine Most big presses use traditional offset commercial printing on genuine Heidelberg printing presses for most of the products they offer

Principle of Operation Offset lithography operates on a simple principle: ink and water must not mix

Visuals and Texts Image information (art and text) is put on thin metal plates that are dampened by water and ink with the aid of rollers on the press

Work Process The oil-based ink adheres to the image area, the water to the nonimage area. The inked area is then transferred to a rubber cylinder or blanket and then onto the paper as it passes around the blanket

A Transfer Method The process explained above is called ‘offset’ since the image does not go directly from the plates to the paper, but is offset or transferred to another surface as an intermediary

Literary Meaning Literarily offset means a printing process in which an inked impression from a plate is first made on a rubber-blanketed cylinder and then transferred to the paper being printed

4 -Colour Printing Method Offset is called a 4 -colour printing technique because like this commercial printing press and inkjet desktop printer both use four basic ink colour: CMYK

Difference from Inkjet Printing Process Where inkjet printing puts all the different ink colours on the paper in one pass through the printer, in offset printing each colour of ink is applied separately one plate per colour.

4 -Colour Process Small dots of the four inks-cyan blue, magenta, yellow and black k-are deposited in specific patterns that make eyes believe one is seeing a wide range of colours. That is why the standard offset process is often called 4 -colour process lithography or 4 colour printing

Spot Colours Offset can also use premixed inks in specific colours including metallic and fluorescent colours called spot colours to obtain hues outside the normal colour range of process printing.

Why use Offset Printing The advantages of traditional commercial offset printing are higher quality and the best costeffectiveness for quantities over a few hundred, especially high volume quantity.

Low Price Per Piece The more you print the less you pay per piece, since most of the cost is in the setup. With a commercial printer, any additional quantity costs only a few cents per sheet for the paper and ink

Brilliant Quality Offset printing produces rich, accurate colour and high quality images and photographs, with sharp typefaces and fine details

Starting Press Runs To start a press run, the imaged plates are clamped onto the plate cylinders and the ink settings are adjusted for the density of ink needed for the particular run

Testing of Machine Runs The press operator runs a batch of initial sheets through the press at low speed and carefully checks registration alignment of the colours and the ink/water balance to ensure full and steady ink flow for accurate colour reproduction.

Adjustments The operator can adjust the plate positions and ink density while the press is running at low speed. This set up process is called a make ready, where highly skilled operator prepares the press for perfect offset printing

Types of Offset Machines There are different types of offset printing presses. There are Sheet-fed offset printing and Web-Fed offset printing

Sheet-Fed Machines Sheet fed offset printing presses run individual sheets, ranging from full size sheet fed presses running sheets that are about 28 x 40 inches to half size and quarter size which use proportionately smaller sheets. They are generally used for business marketing printing

Web Feb Machines Web-offset presses are fed from a large roll of paper that goes through the press in a continuous length of paper, called a web. They are more cost effective for high volume printing catalogues, newspaper inserts and magazines of around 50, 000 quantity or more depending on the size and type of piece.

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