Printing Processes

Question 1

Offset lithography

Answer 1

1. The printing plate is fixed to the cylinder on the printing press.
2. Rollers apply water to cover blank portions of the plate. Water is
   repelled by the emulsion of the image area.
3. Ink is applied by other rollers to the emulsion area and repelled by the
   water

4.The printing plate rolls against a blanket roller (offset cylinder) which
squeezes away water and picks up ink.

5. Paper rolls across blanket cylinder and the image is transferred to the
   paper.
6. The impression cylinder pushes the paper against the offset cylinder
7. There are 4 print units: Cyan, Magenta, Yellow, blacK

Question 2

Flexography

Answer 2

1. A Fountain roller transfers ink onto an anilox roller
   to ensure an even coverage.
2. The anilox roller transfers ink to the raised areas on
   the rubber flexographic printing plate
3. The paper is fed through the press and pushed
   against the rubber roller by the impression cylinder.
4. The image is transferred from the raised areas of the
   rubber roller to the paper.
5. The process is repeated for the CYMK inks
6. The ink can be UV dried.

Question 3

Screen-Printing

Answer 3

1. Original image is placed/drawn/painted onto a transparent overlay.
2. The overlay is placed over an emulsion-coated screen and then
   exposed with a strong light.
3. The areas that are not opaque on the overlay allow the light to
   reach the emulsion which hardens and sticks to the screen.
4. The screen is washed thoroughly. Areas not exposed to light
   dissolve and wash away, leaving a negative stencil of the image
   stuck to the screen.
5. A squeegee is used to spread the ink across the screen and through
   to the T shirt
6. The process is repeated for other colours

Question 4

Gravure

Answer 4

1. Plate cylinders are engraved with the image digitally by a
   diamond-tipped cutter or laser etching machine.
2. The plate cylinder is then partially immersed in the ink fountain,
   filling the recessed holes.
3. Acting as a squeegee, the doctor blade scrapes the cylinder before it
   makes contact with the paper, removing excess ink from non-printing
   (non-recessed) areas.
4. The paper passes between the impression cylinder and the plate
   cylinder under pressure – ensuring even coverage of the ink. The ink
   is transferred from the holes to the paper.
5. Paper passes through a dryer because it has to completely dry before
   going to the next colour unit.

6.The process repeats for each colour (CYMK).