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Offset Litho
Offset Litho Printing
| Question | Answer |
|---|---|
| On what principle does offset litho work? | Offset litho works on the principle that grease and water do not mix |
| How is grease and water used? | Grease on the image areas attracts ink. Water on the non-image areas repels ink. Therefore the plate must be dampened before it is inked. |
| What sort of method is used to print with the plate? | Offset litho presses use a rotary method to print, with the plate wrapped around a cylinder. |
| What are plates usually made from and why? | Plates are usually made from aluminium because it is strong, light and "economically viable" |
| How is the printing image exposed to a plate? | The image is exposed to the plate by photographic methods (usually). 1 - Plate is presensitized 2 - Sensitized plate is put in contact with a film image. 3 - This is exposed to very strong light |
| How is the plate treated after an image is exposed to it? | 1 - Plate is treated with an emulsion developer (lacquer + gum etch in solution of acid) 2 - Plate is then rinsed with water 3 - Gum arabic is used to protect the stencil image on the plate 4 - Plates can be baked to last longer |
Created by:
cloudbusting
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