Colour gamut reduction over time in a coldset process What are its implications? Manfred Werfel Deputy CEO Executive Director Newspaper Production WAN-IFRA GmbH & Co. KG
Colour in coldset ofset We talk much about colour quality Everybody wants to get more colour quality But colour quality is limited by the underlaying basics of the printing proces 2
Paper is made from natural ressources Source: ISO Focus, February 2009 3
Ink on paper isn t it simple like that? 4
Thickness of ink film on paper Ink film, 1 µm Paper, 70+ µm 5
Ink on paper not so simple at all Ink film, 1 µm Coating Paper, 70+ µm WOCG Guide, December 2001 Source: WOCG Guide, December 2001 6
How much ink on a newspaper copy? How much ink do need to print: One newspaper copy 48 pages broadsheet Full colour, 4c 5 g 0,104166666666667 g per page 7
LWC = Light Weight Coated WOCG Guide, December 2001 Source: WOCG Guide, December 2001 8
LWC = Light Weight Coated Ink film Ink penetratio nink film Ink penetration Coating Coating Hole Hole WOCG Guide, December 2001 Source: WOCG Guide, December 2001 9
SC = Super Calendered Ink Paper WOCG Guide, December 2001 Source: WOCG Guide, December 2001 10
NP = Newsprint Ink Paper WOCG Guide, December 2001 Source: WOCG Guide, December 2001 11
Newsprint surface microscopy Enlargement factor: 300 Enlargement factor: 300 12
Newsprint surface microscopy Enlargement factor: 3000 Enlargement factor: 3000 13
Paper/ink combination (extra ink in %) 120 100 80 60 LWC 1 LWC 2 LWC 3 LWC 4 LWC 5 SC 1 SC 2 SC 3 SC 4 SC 5 INP 1 INP 2 INP 3 SNP 1 SNP 2 SNP 3 63 72 95 98 101 100 101 103 40 52 45 How to avoid surprises, Web Offset Champion Group, 2001 34 20 27 0 0,5 5 8 13 Source: How to avoid surprises, Web Offset Champion Group, 2001 14
Coldset is a special print process Newsink never really dryes Newsprint is porous and allows penetration Some ink penetrates into the paper Colours are de-saturated Contrast is limited 15
Why coldest for newspaper printing? Coldset eliminates the need for drying Speeds-up the process Simplifies the process Saves investment, space, paper cost and energy Reduces waste 16
Why is coldset the dominating print process for newspaper production? Short production window Night production Simple process Straight forward process Cost-efficient process Cheapest inks Cheapest paper Not drying cost 17
100 Why coldest for newspaper printing? 80 Coldset replaces drying by penetration 60 The downside of this simplified process includes Lower saturation and contrast 40 Newsprint Smaller colour gamut Lower resolution 20 Gloss-coated, wood-free Excessive dot gain Lower sharpness 0 Lightness Range 18
WAN-IFRA Special Report 2.39 Relationship between density and colour coordinates of primary colours How much can density vary within the framework of the specified colours? 19
Ink penetration Magenta Cyan Black Yellow Source: WAN-IFRA Special Report 2.39, 2004, P. 8 20
Ink penetration Magenta + Black Cyan + Black Blue Yellow + Black Red Green Source: WAN-IFRA Special Report 2.39, 2004, P. 8 21
WAN-IFRA Special Report 02.2007 Andy Williams refers to: Nurmi, Sivonen, VTT ICC profiles for different paper categories the effect of time and print through in the gamut in newspaper processes IARIGAI Conf. 2001 22
Source: WAN-IFRA Special Report 02.2007, P. 11 23
Sample from an Indian newspaper printer Blue Red Magenta Cyan Green Yellow Black Source: A. Williams, A. Srinivasan, 2009 24
Ink penetration study Anand Srinivasan WAN-IFRA Chennai 25
Ink penetration study Ink dry back Effect on colour gamut 26
Ink penetration study Different paper/ ink combinations lead to different colour gamuts 27
Change in density over time Reduction of density over time of ink 1 on paper 1 Status E density, polarisation filter 28
Colour gamut volume reduction v. time 160000 0,03 hours 155000 150000 145000 140000 0,5 1 135000 4 8 12 20 24 36 53 hours 130000 0 10 20 30 40 50 60 Time / Hours Source: A. Williams, WAN-IFRA, 2010 29
Colour gamut 2 minutes after printing 30
Colour gamut 4 hours after printing 31
Colour gamut 4 hours after printing (white) 32
Ink dry-back in coldset Colour gamut may shrink up to 15% through dry-back Effects are mainly desaturation and loss of contrast Biggest change in the first half hour after printing Almost no change after four hours any more Magenta and Cyan dry back most, yellow and black less Colour difference for two-colour overprints can be between 4 or even 6 ΔEab 33
Ink dry-back in coldset Ink/paper combination is critical If certain colour inks dry-back differently colour shifts may happen 34
Before extreme Cyan dry-back 35
After extreme Cyan dry-back 36
Colour shift after dry-back 37
Ink dry-back in coldset Ink/paper combination is critical Test your paper and inks 38
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Ink dry-back in coldset Pressmen measure density on wet copy Reader receives the copy after four hours Pressmen never see the colours that the readers see Find out which wet measured densities lead to which colour result (after 4 hours) What does it mean for soft proofing? Do we need special proofing profiles for wet ink? 40
100 80 b* Web Offset Colour Spaces Coldset, ISO 121647-3 Semi-Commercial, Newsprint Semi-Commercial, SC Paper Commercial Offset, ISO 12647-2 60 40 20 0-80 -60-40 -20 0 20 40 60 80 a* -20-40 -60 41
Don t expect the absolute maximum! Expect the maximum possible for your process Do not try to print better than the standard! Print better with the help of the standard! If a higher quality level is required invest into the appropriate systems Follow the road from coldset to semi-commercial, to heatset drying or UV curing Hybrid systems are possible, but deliver hybrid results 42
What defines colour printing quality? Basic production process parameters define the possible colour quality Neutrality Lightness Contrast Details Sharpness Image resolution Number of colours Colour saturation Colour gamut Absence of defects 43
The colour quality value chain Different production steps influence the final print colour quality Photo shooting Ad design Colour processing Page make-up Data transmission RIP process Plate making Printing 44
Manfred Werfel Deputy CEO Executive Director Newspaper Production WAN-IFRA GmbH & Co. KG Werfel@IFRA.com