BASIC COURSE IN PRINTING TECHNOLOGY

1. BASIC COURSE IN PRINTING TECHNOLOGY

2. The main Printing process • Letter press • Offset Lithography • Gravure • Flexography • Screen Printing • Other Reprographic process

3. Letter Press • Letter Press is a relief process • The image is reversed and it is non readable • The process uses metal type which is hand set or machine set • Pictures are made from blocks made of photo engraving. • Inks are tacky and drying by absorption, oxidation • Used for printing bill books, wedding cards of smaller number say upto 1000 impressions

5. Offset Lithography • It is a plano graphic process • Uses the principle of oil and water do not mix • The image and the non image are in the same plane. • There are three basic cylinders • Plate cylinder (Image carrier – readable) • Blanket cylinder (carries the image) • Impression cylinder (transfers Printing) • The inks are tacky and it is Thixotrophic in nature • Can Print on relatively rougher surfaces • The inks dry by absorption and by oxidation and polymerisation

6. Offset Lithography • Most commonly used press where the number of impressions are any thing from 1000 – 50 ,000 copies. • Sheet fed - cartons, folders, magazine covers • Web offset – magazines , news papers etc • Low preparatory costs when compared to other process • Operation skill required is very high

8. Gravure • Intaglio process – the image area is recessed • The gravure cylinder where the image is etched ( image carrier) is immersed in a pool of liquid inks • The inks are carried by the cylinder and the excess ink is wiped by the doctor blade • The impression from a rubber roll makes the ink to transfer to the substrate through capillary action • The image is non readable • Mostly economical where the run length is very high

10. Gravure • Most common application are cigarette, flexible laminates, currency notes etc. • The initial cylinder costs are very high which is justified only if the run length is high • Requires very smooth surface as the image is direct contact with the substrate • Also good compressibility ensures better printing • Produces a continuous tone effect in the image

11. Flexography • A form of relief Printing uses rubber or resilient plastic plates ( photo polymer plates) • The inking system uses a special annilox roller immersed in liquid inks • Inks dry by evaporation • Uses water based inks and is most friendly for food packing applications • For large runs of liquid packaging, getting popularity in publishing abroad

12. Screen printing • It is a stencil process • Can print on any surface • Uses high tack paste inks • Used for very short run job as the initial cost is less • Used for printing visiting cards, textile printing etc.

13. Printing a job • The ad agency or the customer prepares a rough layout or dummy • The customer gives the copy for reproduction which can be text matter, line drawings, photographs etc • The customer prepares a mechanical layouts which shows the position and others which is called art work • The type setting is done

14. Quality and Productivity Litho – Offset Print Production Photographic Originals

15. Quality and Productivity Litho – Offset Print Production Artists’ Originals

16. Quality and Productivity Litho – Offset Print Production Graphic Originals

17. Quality and Productivity Litho – Offset Print Production Text ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz 1234567890 `~!@#$%^&*()-_=+;:’”,<.>/? ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz 1234567890 `~!@#$%^&*()-_=+;:’”,<.>/?

18. Quality and Productivity Litho – Offset Print Production Digital Originals

19. Printing a job … contd • The photographs, pictures which are continuous are scanned. • The text and pictures are combined as per the art work • After these they are assembled to make a negative • Depending on the plates, negative or positive is exposed with the plate to give the Plate for printing

20. Printing a job … contd • The plate is developed after exposure and is mounted on the printing machine • The printing takes place with the help of the ink and the image from the plates • After printing post printing operations like cutting , varnishing, punching are done

21. Colour theory • Additive primaries – Blue , green, red – The combination these three coloured lights give white light. The principle used in TVs, computer monitors etc • Subtractive primaries – Maganta, cyan, yellow –The combination othese three pigments/dyes give black – Used in printing, painting etc

22. Colour Measurement Human Vision

23. Additive Colours

24. Colour Measurement Colour MonitorsRGB RGB RG GB G RB R B K

25. Colour theory 4 Colour printing – A picture is scanned and four positives of cyan , yellow , maganta , black are taken Cyan – Red filter Maganta – Green filter Yellow – Blue filter Black printer – Under colour removal

26. The process of printing • The printing process is done through dots. • The tonal gradation is achieved through varying the size of the dots but the number of dots remain same. • The number of dots in a square area determine the resolution of the picture • The half tone process is done through screens in printing.

31. Paper Properties and their relation to Printing • Caliper/Bulk/Density • Determines the pressure required to get good Print • Uniformity in caliper to minimise variation across the sheet • Bulk/density determines the print reproduction in direct contact process • Creasing and folding property

32. Paper Properties and their relation to Printing • Smoothness/Roughness • Determines the ink transfer and dot reproduction on the surface • Final Print gloss and Varnish Gloss • Dot Gain

33. Impact of smoothness and Coating newsprint coldset art paper glossy inks

34. Quality and Productivity Litho – Offset Print Production Dot Gain Dot size on print Dot size on scanners display Dot gain

36. Paper Properties • Colour • Expressed as Whiteness, Brightness and L, a, b values. • Print colour reproduction (shade Matching)

37. Paper Properties • Moisture and Dimensional Stability • Runnability in web feed process • Blistering in Heat set web offset • Register control in sheet fed offset • Folding and Creasing

38. Paper properties • Tensile Strength • Runnability in web feed process • Pack formation in flexible laminates • Pick strength • Ability to take high tack inks • Ability to run at faster speeds

39. Paper Properties • Water Absorbency • Ink drying • Dimensional stability • Ink Absorbency • Post Print gloss • Pick strength • Ink drying

40. Thank you