Printing Methods Notes

Lithography uses oil-based ink and water and works on the principle that oil and water don't mix.

1. Ultraviolet light used to transfer image onto smooth aluminium printing plate 

2. Image area gets coated with chemical that attracts the oily ink but repels water;                           (so image area holds ink and non-image are holds water)

Offset lithography - image is printed onto rubber 'blanket' cylinder which squeezes the water and transfers ink to paper.

Print runs: Large (1000 copies or more)

Advantage: Fast ways of printing, High quality product

Disadvantage: Expensive set-up cost

Examples: Books, newspapers, magazine

Video Link: https://www.youtube.com/watch?v=pNZb7CXUjs0

Left: Lithography                                                                Right: Offset Lithography

Gravure uses an etched brass printing plate (meaning the image is lower than surface of the plate and the ink fills the etched bits)

1. The cylinder rotates through an ink pan where the cells pick up ink.

2. The excess ink on non-image area is scraped off the cylinder by a doctor blade before ink is transferred directly to paper board surface.

3. The transfer of ink from cylinder is aided by electrostatically charging the impression roller.

Print run: Extremely Large (a million copies or more)

Advantage: Fast printing speed, Excellent quality

Disadvantage: Expensive to set up

Examples: Postage stamps, Photos in books, Catalogues, Colourful magazines

Video Link: https://www.youtube.com/watch?v=xialgxiIpNk&index=8&list=PLLJC 3McJVVm41ChU3qZkTY_w3YOH2iyj

Link to Website: https://www.iggesund.com/en/knowledge/the-reference-manual/printing-and-converting-performance/Gravure-printing/

Flexography uses a printing plate made of flexible rubber or plastic. The image sticks out abit from the plate. You can print on different surfaces, including surfaces which are not smooth such as cardboard, plastic bottles. 

Print runs: Large (Over 5000)

Advantage: Quicker than lithography, printing plate last longer

Disadvantage: Expensive set up costs

Examples: Packaging, Carrier bags and Wallpaper

Video Link: https://www.youtube.com/watch?v=n78aMkZOZDg

Link to Website: https://www.iggesund.com/en/knowledge/the-reference-manual/printing-and-converting-performance/Waterless-offset-printing/

Screen Printing - stencil is put under fine mesh screen, ink is spread over the top. The ink goes through stencil and prints onto the material.

1. Fine mesh strectched over a frame & Stencil is used to mask area that do not require colour.

2. The ink is then forced through screen with a squeegee.

3. Photonegative is placed on screen & where UV is exposed, the material's surface hardens. 

4. Excess is washed away with pressurised water jet. Gaps in material allow ink to flow through

Print size: Short (1000 or more)

Advantage: Low cost process, Various surfaces including textiles

Disadvantage: can be slow (mechanical system available), Decent quality only

Examples: Posters, T-shirts, Estate agent's signs

Video Link: https://www.youtube.com/watch?v=cKqD6WkGZdo

Link to Process Website: http://graphicdesign.stackexchange.com/questions/26710/what-printing-process-is-better-to-avoid-t-shirt-logo-damage

Digital Printing is done using inkjet and laser printers.

1. Ink in powder form (toner) held in trays is applied to paper or card using electrostatic charge.

2. The laser neutralises the charge on the drum.

3. Toner only sticks where electric charge is and rollling drum applies this to the paper.

4. Toners are supplied in CMYK colours.

Laser Printing works on principal that like charged particles repel and opposite charges attract.

Don't need to have many printing plates, so no set-up costs apart from buying a printer and ink cartridges (which may need replacing)

Advantage: No set up costs, instant one-offs

Disadvantage: Expensive item cost, Short print runs

Examples: Posters, Flyers, Digital photos

Video Link: https://www.youtube.com/watch?v=WB0HnXcW8qQ