Printing

Question 1

Offset lithography

Answer 1

Principle
- Oil and water dont mix

Products
- posters, books, newspapers, packaging

Process
1) Image prepared digitally and transferred to a metal printing plate (one for each colour: CMYK).

2) The plate is dampened with water (non-image areas attract water).

3) Then ink is added – it sticks only to the image areas.

4) The image is transferred (offset) from the plate to a rubber blanket.

5) The rubber blanket then prints the image onto paper.

pros
- good quality, inexpensive, high speed

cons
- paper can get wet, expensive ser up costs

Question 2

Flexography

Answer 2

Principle
- Relief printing

Products
- plastic bags , warappers

Process
1)A flexible rubber or plastic printing plate is made with the image raised (like a stamp).

2)The plate is wrapped around a rotating cylinder.

3)Fast-drying ink is applied using an anilox roller (which controls ink flow).

4)The plate transfers the ink directly onto the material (e.g. paper, plastic, film).

5)The printed material dries quickly, ready for finishing or cutting.

pros
- high speed, fast drying
cons
-high set up costs, dificult for fine detail

Question 3

Screen printing

Answer 3

princliple
- stencil method

products
- posters, T-shirst, signage

process

1) A fine mesh screen is prepared with a stencil of the image (blocks ink in some areas).

2) The screen is placed on top of the material (e.g. fabric, paper).

3) Ink is poured onto the screen.

4) A squeegee is pulled across the screen to push ink through the open areas of the stencil.

5) The material is left to dry, or dried using heat.

pros
- easy to produce stencils, print onto any surface, produce large volumes

cons
- hard for fine detail
- longer drying times

Question 4

Gravure

Answer 4

principle
- intaglio printing

products
- labels, magazines , postage stamps

Process
1) The image is engraved as tiny cells onto a metal printing cylinder.

2) The cylinder is coated in ink – ink fills the engraved cells.

3) A doctor blade scrapes off excess ink from the surface, leaving ink only in the cells.

4) The paper is pressed against the cylinder, and ink is transferred from the cells to the paper.

5) The print is dried and the material moves on.

pros
- high speed, consistent colour, high quality

cons
- expensive plates, very expensive set up costs, can see dots printed.