V. Write a short summary of the text. Text 5 Other traditional printing techniques

The use of stencils to apply an image goes back many centuries, but it was only at the beginning of this century that this was allied to the use of a screen, thus giving the process its name. It is the most versatile of the printing processes.

The process A stencil, cut by hand or made photographically is supported on a screen of synthetic fibre or metal. Originally, this screen was made of silk — hence the name 'silk screen printing'. The screen is stretched tightly over a frame of wood or metal, and ink is spread across the screen by means of a rubber squeegee, which squeezes the ink through the screen in the image areas. The stencil prevents ink going through in the non-image (background) areas.

Uses of screen printing The fact that the process can apply a very thick film of ink makes it ideal for posters. Also, virtually any type of material can be printed on, including wood, fabric, glass, plastic and metal. Screen printing is therefore used for plastic and metal signs, bottles (even printing on their inside surface), transfers and electronic circuits. It can also print on very light papers and is therefore used for printing dressmaking patterns.

Flexography.This process is a derivative of letterpress, using flexible plates and thin, fluid inks that dry by evaporation (sometimes assisted by heat). The plates are made from rubber or photopolymer and the image is raised as in conventional letterpress. Most flexographic presses are web-fed because of the nature of the products they are usually used to print. Ink is applied to the plate by a metal roller; this roller, known as an anilox roller, has cells etched into it which hold ink and transfer it to the flexible plate for printing. Many machines are multi-colour, for four-colour work.

Uses of flexography: Flexography is used mainly for packaging — printing on cellophane, plastics and metallic foils; in fact, it can be used to print on virtually any material that will physically pass through the press. It is used also to produce some of the less expensive magazines as well as local and national newspapers.

Collotype This process (also known as 'photogelatin') is, like lithography, a plano graphic process. It is now rarely used, but this process is the only one that can produce high-quality black-and-white or colour prints without the use of a screen. It can print gradations from the deepest black to the lightest tones of grey with extremely high-quality results and is sometimes used for printing small runs of fine-art reproductions.

Collotype presses run at particularly slow speeds; it may take two days to produce 2,000 sheets — the maximum that can be taken from any one plate.

Die stamping and copper engraving This, like gravure, is an intaglio process, where a steel or copper plate is engraved by hand or etched using photographic techniques to create a recessed image. The process is used for high-quality business cards, letterheads and invitations. Rotary versions of this process are used also in banknote and security printing.

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