Choosing the right print coating

The right coating can help protect the printed piece or add a creative dimension. The results will usually look best on coated paper because the hard, nonporous surface of coated paper holds the coating on the top of the paper rather than have it disappear by being absorbed into the paper. Even when trying to achieve an overall matte effect, a gloss coated sheet is usually the best paper choice and the gloss finish on the paper will provide superior printability. In general, uncoated papers do not benefit very much in appearance from coatings or varnishes, although either will help prevent rubbing in areas of heavy ink coverage. Matte or satin varnishes or coatings are the best choices for uncoated stocks.

Varnishes
Varnishes are applied on press like any other ink and can be tinted to create a special effect. Although gloss and matte varnishes are typically used as spot or overall coatings, they can also be incorporated in the process or spot color inks in order to provide a unique look to the presswork. They can be wet trapped (i.e. printed at the same time as the other inks) or dry trapped (i.e. printed as a second pass through the press after the other inks have dried). Dry trapping provides a superior result but is a more expensive process. Varnishes may yellow with age, however, this is usually not noticeable when the varnish is used over process colors, but it is noticeable when the varnish is applied over unprinted paper. They also require the use of offset spray powder on press to keep the printed sheets from sticking together before the varnish is completely cured. The powder left behind can adversely affect the look and feel of the finished piece.

Gloss varnish: This coating can be applied overall or in spot areas with high precision. A gloss varnish increases the saturation and depth of colors while improving image contrast. It provides good protection against rub-off but some fingerprinting will be apparent on dark or light colors. Because the gloss finish is highly reflective it creates glare on the surface of the print which may impair the readability of text.

Matte varnish: This ink protects the sheet with a non-reflective coating which enhances the readability of text-heavy pages. Using a matte varnish over images tends to flatten and soften them, but it can provide a lush tactile quality to the paper surface. As with a gloss varnish the coating is printed with a litho plate, so it can also be spot applied with high precision. It is more resistant to fingerprinting than a gloss varnish however it will tend to scuff or gloss up with wear. If the presswork is packed for delivery it's a good idea to place blank paper between the printed items to prevent them rubbing against each other and scuffing.

Satin varnish: This coating is created by mixing gloss and matte varnishes together and offers an intermediate level of shine, with good scuff resistance.

Opaque varnish: Adding a small amount of opaque white to a varnish can give it a slight opacity which can help in creating a stronger separation between a gloss and a matte varnish. Adding a slight contamination with silver ink can accomplish the same effect on very dark colors.

Strike-through matte varnish: A litho plate printed varnish that, when overprinted with an overall gloss UV or aqueous coating, will create a visual separation between areas of a press sheet. Gloss/matte effects work best on dark colors, or when enhance by the content of underlying graphics.

Aqueous coating
These water-based coatings are applied using a rubber blanket inline on a special dedicated press unit. among the most commonly used coatings available today and provide good protection from fingerprints and other blemishes. Aqueous coatings are less likely to yellow and are more environmentally friendly than varnishes. They dry faster than varnishes which translates into faster turnaround times on press. They don't require spray powder. Because they seal the ink from the air, they can help prevent metallic inks from tarnishing. Aqueous coatings can cause certain spot colors such as reflex blue, rhodamine, violet, purple, and PMS warm red to change color. Sometimes within a few minutes but also over time - months or even years later. Because the aqueous coating is water-based an typically applied over the entire sheet it is best to use at least an 80# text weight or heavier paper to prevent the paper from curling, distorted, or wrinkled.

Gloss aqueous: Usually applied as an overall coating, gloss aqueous offers better protection than gloss varnish. It is sometimes applied to a spot area however this requires cutting an expensive press blanket. It also results in edges that are not as sharp as a spot varnish and registration that is less precise. The surface dries instantly, making it an excellent choice for short run work-and-turn projects. Aqueous coatings help disguise surface flaws and roughness in the non-print areas of inexpensive papers. The gloss finish improves the apparent saturation of ink but somewhat reduces the readability of text.

Matte aqueous: A scuff resistant matte coating which, as with gloss aqueous, is generally applied overall. And like a matte varnish it will soften and flatten images slightly.

Satin aqueous: A popular compromise between gloss and matte, offers a pleasing sheen and good sheet protection.

SoftTouch aqueous: A proprietary coating that is applied with a special metering roller to create a suede-like texture and extreme matte appearance.

Pencil receptive aqueous: This is a special matte aqueous coating that is designed to be pencil, ink and laser receptive.

Dry erase aqueous coating: An inexpensive high gloss alternative to lamination to make any paper suitable as dry erase marker surface.

Primer aqueous: A coating that is applied before lamination, or to difficult substrates to make them ink receptive.

UV Coatings
UV coatings are applied inline by printers or offline by finishers or converters. They are applied as a liquid, using a roller, screen or blanket, and then exposed to ultraviolet light to polymerize and harden the coating. Like aqueous coatings, UV coatings can cause certain spot colors to shift in hue. Some UV coatings may have a strong odor.

Gloss UV: Creates the highest printable overall gloss coating. Depending on the printer's equipment it can be applied to spot areas.

Matte UV: Depending on the printer's equipment it can be applied overall or just to spot areas. It is prone to fingerprinting.

Pearlescent UV: These gloss coatings include miniscule metal flecks in red, blue or silver, giving a pearlescent appearance.

Orange peel UV: A slightly raised, textured finish, gives this coating a unique tactile and visual quality that is similar in appearance to thermography.

Inks beyond CMYK, Hi-Fi, and Pantone - the world of effects pigments

Printers and their customers are always looking for new ways to add value and a creative spin to print. When conventional CMYK, Hi-Fi, and Pantone spot colors just don't have the impact - it's time to look at the options available with effects pigments.

Here is a run down of the most popular effects ink pigments. Savvy printers will pretest and, based on their understanding and relationship with their customers, make them aware of the creative opportunities these inks provide.

Photochromic inks
Arguably one of the most popular of the effects inks. Photochromic ink undergoes a reversible color change when exposed to UV light. The color change is immediate and reverts to its original color or becomes colorless when the light source is removed. This ink is available in wet or dry offset and flexographic printing.

Austria Solar's 2011 annual report uses photochromic inks to parallel the company's business. It ships in a foil package. Open it under indoor light and all you’ll see is an embossed cover followed by blank pages. However when exposed to the sun the photochromatic inks react and the content is revealed. The report is the creation of agency Serviceplan and Creative Director Cosimo Möller.
Photochromic inks are available in colorless-to-color and color-to-color formulations.
Photochromic ink viewed under office lighting.

Photochromic ink viewed under sun light.
Thermochromic inks
Thermochromic inks are temperature-activated. When rubbed, held in the hand, or exposed to differing temperatures the ink changes from a colorless state or to another color and quickly reverts to its original color.
As with photochromic inks, thermochromic inks are available in colorless-to-color and color-to-color formulations. The temperature when the color change occurs can be predetermined - e.g. color appears at 72°F and becomes colorless at 90°F or color appears at 81°F and becomes colorless at 90°F.

Hydrochromic
This ink is activated by water, not sunlight or heat. A white hydrochromic ink just looks like white ink. When water is applied, it disappears and the image behind it appears. When the water dries, the image goes back to white.

UV Fluorescent
These inks are normally invisible as printed but fluoresce under UV light. There are two types; single long wavelength (360 nm) and dual which fluoresces one color under short wavelength UV (250 nm) and a different color under log wavelength UV (360 nm). Typical UV fluorescent color inks include yellow, green, blue, orange, and red. These inks are often used in banknote printing. This ink is available for wet or dry offset, flexographic and gravure printing.

Optically Variable Ink
This ink contains minute flakes of metallic film which, when viewed at different angles, morphs from one color to another very dramatically. This ink needs to be printed with a fairly heavy weight to get the best results which makes the ink feel almost embossed on the substrate. The ink are very expensive and therefore is usually printed in small areas. The most common color changes are brown to green (and vice versa) as well as red to purple. It is typically used for passports and driver's licenses.

Bleeding
Bleeding ink prints in black but when exposed to any aqueous solution it will produce a red stain - even when touched with just a wet finger. This ink is only available for use with dry offset printing.

Fugitive Ink (water based)

Fugitive ink works similarly to bleeding ink since when exposed to water or an aqueous solution the ink runs. These, also, will be found on checks and if you are to wet your finger with saliva and wipe across the background, you would see the ink smudge.

Coin Reactive
The image printed from this ink is white or transparent. The image is revealed when the edge of a coin is rubbed over the ink. Coin reactive ink cannot be scanned or copied.

Erasable
Erasable ink is used on the background of a document. If an eraser is rubbed on it the ink rubs off in that area. The ink also reacts in the same manner as solvent/chemical reactive inks do. Erasable inks are typically used on scenic or pantograph backgrounds on checks and certificates. This ink should not be used for documents that will go through a laser printer.

Iridescent
Iridescent ink is a translucent pearlescent ink which, when viewed at different angles, creates a subtle change of iridescent hues. It is available in blue, red, green, gold, and silver.

Metameric Pairs
Metameric pairs are two inks that appear similar in color under one set of light conditions but are visibly different under another set.

Puff Ink
Puff ink rises and expands ("puffs") when exposed to a heat source.

Glow in the Dark Ink
This ink radiates a bright light green color after being exposed to bright light and then placed in a relatively dark environment.

Penetrating Ink/Indelible Ink
Penetrating inks contain a penetrating red dye that goes into the fibers of the paper and will show through to the back of the document. Penetrating inks are commonly used on the arabic and MICR numbering of negotiable documents to deter forgers from trying to scrape the number off from the document. If the number is scraped off the red stain remains on the document. Penetrating inks are available for letter press or wet offset printing.

How to subdue the Reflex Blue Blues

Reflex Blue (a.k.a. Red Shade Alkali Blue, Pigment Blue 61, Reflex Blue R 54/R 56) is one of the most commonly used spot colors - especially for corporate colors - and it is one of the most problematic inks to use on press.

Reflex Blue suffers from excessive marking, low scuff resistance, poor lightfastness and poor, very slow, drying qualities. It also has a bronzed look that causes it to shift color, from Blue to Purple when viewed at different angles.

And when mixed as part of another blue spot color, Reflex Blue effectively contaminates that ink color with its poor performance characteristics.

Reflex Blue Blues - slow drying

Printing inks are made primarily with resins, varnish, linseed oil, soybean oil, or a heavy petroleum distillate as the solvent (called the vehicle) combined with organic pigments. The resins and varnish control the tack and gloss of the ink while the solvents control press stability and fluidity. Drying oils control surface strength, drying time, and set, while the pigment acts as the coloring agent.

Although each ink pigment is unique, most have fairly uniform shapes and surface areas. Reflex Blue pigment on the other hand has jagged, irregular surfaces and shapes. To blend Reflex Blue ink, ink manufacturers must add surface active agents to the mix that allow proper wetting of the pigment. As a result, the ink retains a higher level of moisture than other ink formulations and therefore takes longer to dry.

Offset inks are generally designed to dry by two methods: absorption into the paper and evaporation from the surface. As the ink dries, the small, uniform color pigments settle close together and leave a flat ink film surface. However, when Reflex Blue pigments set they have a rough ink film surface. Although the ink may feel dry to the touch, just a light rub will break the surface and expose the wet pigment underneath. This results in unsightly scuff marks and color transfer (set-off) to surfaces that come into contact with it.

Reflex Blue Blues - color shift/burn out

Reflex blue  color-shift or "burnout" can occur when the printed ink film is over-coated with aqueous, or UV coating.  This affect results from a chemical reaction due to pH incompatibilities between the alkaline aqueous coating and certain alkaline sensitive ink pigments like Reflex Blue. The chemical reaction basically changes the way the color pigments reflect light. Individual press sheets pulled during the press run or top sheets in the pile are rarely as affected as the sheets within in the press loads. This indicates that heat and oxygen deprivation are contributing factors in accentuating and accelerating, the color-shift effect. Unfortunately the color-shift may not be apparent immediately off press and may take 24 hours or longer to be noticeable.

Tips for subduing the Reflex Blue Blues

1 Don't use it. If that's too drastic then:
If you are a printer, speak to your ink vendor. Most will stock an "imitation" Reflex Blue substitute. The most common is a Carbazole Violet & Phthalo Blue mix. Note that the imitation Reflex Blue may have a slightly different hue than the actual Reflex Blue so do a drawdown of the ink and get customer approval.

If you are a print buyer/specifier, speak to your print supplier about selecting an "imitation" Reflex Blue substitute. Get drawdowns of the ink and, once satisfied with the hue, document the ink manufacturer, ink series and name so that the same ink can be used for all your Reflex Blue needs.

2 Print the job using UV inks since they dry immediately.

3 Print small lifts. Shorter stacks of paper at the press deliver facilitate faster drying by allowing more air to circulate between sheets enabling gasses to escape. Shorter stacks will add a small amount of extra run time on press. Wind the printed loads as soon as possible to reduce unnecessary exposure to high heat builds captive in the pile.

4 If the shop runs a five day production schedule then print on Friday to allow the sheets to dry over the weekend before printing the second side or sending the presswork to the finishing/binding processes.

5 Consult with the printer/ink vendor to determine whether reformulating the Reflex Blue ink by adding drying agents. Note that doing so may increase cost and/or compromise the inks on press performance in other ways - e.g. it may adversely affect te quality of screen tint areas.

6 Apply a varnish, aqueous or UV coating to help seal the ink and eliminate scuffing, fingerprinting, and bronzing of larger ink areas. Use a low-amine or heat-resistant aqueous coating with as low a pH as possible (less alkaline). Inform your ink supplier of the need for alkali or fade resistant inks compatible with aqueous or UV coating and also consult with you coatings supplier and are assured of these pigments’ compatibility with their product. Confirm that the coating to be applied has been thoroughly tested prior to running the job.

7 Beware that UV coating, in particular, does not coat well over Reflex Blue and will sometimes fade or change the ink color. Pre-test Reflex Blue, especially tint solids and screens, by wet-trapping half the image with selected coating and then expose both samples to a high-heat source such as a heated saddle dryer. On-press testing is usually required to simulate actual production with ink and fountain solution. For side-by-side comparison, cut the coater blanket packing half-way through the printed ink film to be tested. Then expose the coated and uncoated print samples to a heated dryer saddle immediately off press. Burnout and color-shift will usually occur during heat application. If time permits, wait 24 hours, then reapply heat, and again compare the color integrity of the test samples. Test, test, test.

Other alkali sensitive pigments that can have similar issues to Reflex Blue include:
• Rhodamine Red - (Y.S. Rhodamine Red)
• Purple - (B.S. Rhodamine Red)• Warm Red - (Red Lake C)
• Violet - (Methyl Violet)
• 072 Blue
• Rubine Red - (Lithol Rubine)
• Fluorescent inks

In One Quarter of a Second on Press

Printing presses whether they're an older manual model (like the one pictured) or a modern computerized system, share one purpose in common - they must be able to lay down a film of ink with remarkable precision and consistency.

For a typical offset press, one ink tower delivering one of the four primary colors in full color printing lays down an image covering an area approximately 40" x 28". That image is formed by splitting a film of ink 4 microns thick (a tenth the thickness of a human hair) twice (plate to blanket then blanket to paper), while at the same time emulsifying it in a chemical solution (made primarily of water) to a depth of a few molecules. Too much water and the ink washes away. Not enough water and ink starts to print in the background. The ink is carried by approximately 19,250,000 halftone dots averaging in size from 10 to 60 microns. The final film of ink deposited on paper over the whole 1,120 square inch area of the image and is held to a thickness of about 1 micron (one fortieth the thickness of a human hair) with a tolerance of +/- one-tenth of a micron. The positional accuracy of the image is held within one-three hundredths of an inch - about 40 microns. All in one quarter of a second on press.

Slur

Slur is often confused with doubling as their initial appearance is very similar. However slur is invariably an elongation of the dots in the sheet travel direction. The usual cause of slur is either over or under cylinder packing. Loose blankets, too much plate-to-blanket pressure, too much ink on coated paper, and ink rollers set too hard will also cause slur.

Doubling

Doubling is often confused with slur as both exhibit an elongation of halftone dots. However, slur is usually an elongation in the direction of sheet travel through the press while doubling can be in any direction. Doubling (and slur) often manifest as a problem with the range of tones available in the presswork being compressed and loss of detail, particularly in the shadow areas (a.k.a. muddy halftones). Doubling can be caused by many of the same factors as slur. When the cylinders rotate the halftone dots are not placed in exactly the same position with every revolution. As a result the dots print up as double or multiple images. Doubling between units occurs when a blanket picks up a previously printed ink film. This is known as backtrapping. Examine the dots, or line art graphics, under a loupe to confirm whether the problem is doubling or slur.

Ink and Paper - a video portrait

Film maker Ben Proudfoot has made a beautiful short documentary about two, next door neighbor shops - one a paper shop and the other a print shop - both struggling to survive.

Aardvark Letterpress
2500 West 7th Street
Los Angeles, CA
(213) 388-2271
http://www.aardvarkletterpress.com/

McManus & Morgan Paper
2506 West 7th Street
Los Angeles, CA
(213) 387-4433
http://www.mcmanusmorgan.com

Pantone color shifting - the problem with coatings

I think that most of us have been hit with an unpleasant surprise when a Pantone ink color shifts after being UV or aqueous coated. As one example, Reflex Blue (arguably the most difficult color in printing) prints as dark blue but will dry with a reddish sheen that will not dry properly. To try and make it dry faster the printer might run it through the press a second time to apply a coating, either UV or Aqueous, to seal the ink. This causes an immediate color shift which will continue to shift over the course of a few days.

The colors in the table below, as well as any spot color recipes that use them in the formula, will shift color (a.k.a. alkalinity burn) when subjected to the alkalinity of a aqueous or UV coating.
In order to avoid the costs involved with reprinting a spoiled job, when mixing and/or specifying PMS colors it's critical to inform your ink vendor that you will be aqueous or UV coating the job.

Special thanks to Bob Peterson of Superior Ink for his contribution to this post.

Printers and Ink - wherever you go, there you are!

Printers Alley, Nashville, Tennessee, United States
Ink Street, Carletonville, Gauteng, South Africa
Printers Alley, Doylestown, Pennsylvania, United States
Ink Wells Drive, San Antonio, Texas, United States
Printers Place, Darwin, Northern Territory, Australia
Ink Road, Iowa, United States
Printers Lea, Balgrochan, United Kingdom
Ink Street, Rochdale, United Kingdom
Printers Lane, New Haven, Conneticut, United States
Ink Lane, North Melbourne, Victoria, Australia
Printers Alley, Middlebury, Vermont, United States
Ink Drive, Redding, California, United States
Printers Parkway, Colorado Springs, Colorado, United States
Graphics Way, Lewis Center, Ohio, United States
Graphics Drive, Tinley Park, Illinois, United States
Graphic Way, Westerville, Ohio, United States

Printing Standards and Specifications

Printing standards and their associated specifications bring an independent, authoritative, and concrete basis for file preparation, proofing, presswork, and output evaluation. They reduce proofing cycles and enable faster approval processes. They also help synchronize expectations between print buyer and print provider.

I'll begin with a few definitions.

A Standard according to the International Organization for Standardization (ISO) defines a standard as:
"A document established by consensus and approved by a recognized body that provides for common and repeated use, rules, guidelines or characteristics for activities or their results, aimed at the achievement of the optimum degree of order in a given context."

A Specification is not a standard. Rather, it is a detailed description of the criteria for a piece of work. Specifications for printing can include characterization-data, ICC-profiles, PDF preflight criteria, calibration targets for the print process, etc.

A Method is usually defined as a way, technique, or process for doing something. It is a recipe.

To use a cooking analogy - a standard represents the desired final outcome, for example a cake.The specifications describe the ingredients needed to make the cake. The method describes the steps required to make the cake. There can be many different methods to achieve the desired standard based on the specifications.

The most important standards for print production are:


• ISO 12647
 which describes color for different types of presswork (sheetfed, heatset web, coldset web, etc.). Of all of the standards within the Graphic Arts, what is of most importance to most printers and print buyers are contained within the ISO 12647 family.
ISO 12647 is broken down as follows

ISO 12647-1 Parameters & Measurement methods
ISO 12647-2 Offset Lithographic processes
ISO 12647-3 Coldset Offset Lithography on Newsprint
ISO 12647-4 Publication Gravure
ISO 12647-5 Screen Printing
ISO 12647-6 Flexo Printing
ISO 12647-7 Proofing process from digital data


• ISO 2846-1
 which describes ink color and transparency.


• ISO 3664 defines lighting conditions for viewing color copies and their reproduction with either incident or transmitted light.


• ISO 15930-X 
(PDF/X) for data exchange in print production.


• ISO 15076 for the ICC color profile format.


• ISO 12640 for the data format from which ICC profiles are calculated.


The most important specifications for standardized print production are:


PSO Process Standard Offset printing developed by FOGRA / bvdm / ECI

This implementation of ISO 12647-2 is included with most digital proofing solutions used in Europe and is pre-configured with the UGRA FOGRA Mediawedge for verification.
Grey balance target values in PSO are done by comparing K- and CMY-patches with similar grey side by side. PSO does not contain procedures and tolerances for judging grey balance by measurement.
PSO also includes the possibility of a certification for pre-press and printing.


GRACoL/SWOP managed by IDEAlliance


These standards take their basis from ISO 12647-2 but place a higher importance on grey balance during calibration and the press run compared with the PSO. Most proofing solutions for the North American market include the needed setup to produce proofs that represent the GRACoL/SWOP target.


System Brunner


System Brunner is a standardization method for print production. It places a very strong emphasis on grey balance (in combination with TVI and Solids) for controlling and certifying the press run. System Brunner is included with some printing press manufacturer's press control solutions.
It can also be combined with PSO, SWOP, or GRACoL.

There are various ISO 12647 standards according to the main types of printing methods. Here I will try and cover the essentials of just one of these - ISO 12647-2 - as an example of the type of specifications that guide printers to achieving the standard. Note that specifications do change over time, so, although the information I present is correct (as far as I know) the actual current published standards should be your guide.ISO 12647-2 specifies a number of process parameters and their values to be applied when preparing color separations for four-color offset printing by one of the following methods: heat-set web, sheet-fed or continuous forms process printing, or proofing for one of these processes; or offset proofing for half-tone gravure. Note that the specifications are based on plates imaged in a film, not CtP, workflow.

ISO 12647-2 is
▪ directly applicable to proofing and printing processes that use color separation films as input
▪ directly applicable to proofing and printing from printing formes produced by filmless methods as long as direct analogies to film production systems are maintained
▪ applicable to proofing and printing with more than four process colors as long as direct analogies to four-color printing are maintained, such as for data and screening, for print substrates and printing parameters
▪ applicable by analogy to line screens and non-periodic (i.e. FM) screens.

ISO 12647-2 Type 1 for offset lithographic processes on gloss-coated paper specifies:
Ink: ISO 2846-1
Substrate: L* 95 a* 0 b* -2
Primary Colors (black backed): K: L* 16, a* 0, b* 0 , C: L* 54 a* -36, b* -49, M: L* 46, a* 72, b* -5, Y: L* 87, a* -6, b* 90
Secondary Colors (black backed): R (M+Y): L* 46, a* 67, b* 47 , G (C+Y): L* 49 a* -66, b* 24, B (C+M): L* 24, a* 16, b* -45, C+M+Y: L* 22, a* 0, b* 0
Solid ink densities: (informative information)*
Halftone screen: 133 lpi, 150 lpi, 175 lpi, 20 micron FM
Dot Gain/TVI: 12 -16% or 18 -22%
Grey Balance: 25%-19%-19%, 50%-40%-40%, 75%-64%- 64%
Neutral definition: substrate or equivalent tone of black
ISO profile: ISOcoated_v2_eci.icc
Characterization data: Fogra39L.txt

GRACoL 7 The General Requirements and Applications for Commercial Offset Lithography publication that is a common reference in North America and is based on ISO 12647-2 specifies:
Ink: ISO 2846-1
Substrate: ISO 12647-2
Primary Colors: ISO 12647-2*
Secondary Colors: ISO 12647-2*
Solid ink densities: Not specified
Halftone screen: 175 lpi AM round dot
Dot gain/TVI: Not specified - replaced by Neutral Print Density Curve values: @ 25% Grey: CMY .25/K .22, @ 50% Grey CMY .54/K .50, @ 75% Grey: CMY .90/K .90
Grey Balance (required): 50%-40%-40%
Neutral definition: a* 0 b* -2
ICC profile: GRACoL2006_Coated1v2.icc
Characterization data: GRACoL2006_Coated1

Some peculiarities of ISO 12647-2 and GRACoL 7

Where GRACol 7 differs from ISO 12647-2 (as per the implementation guidelines of PSO (Print Standard Offset-print)) is the method used for adjusting the mid-tones. The PSO advises adjusting the inking until the TVIs of CMY come close to their aims, while GRACol 7 would have the neutral densities of the CMY and the K grey patches brought close to the prescribed aim values regardless of the individual TVIs that result. In practice this means that each color will have a different TVI curve to achieve the neutral grey. GRACol 7 allows for deviation of primaries in order to obtain grey balance.

ISO 12647-2 includes the following chart of dot gain/TVI curves:There are a few peculiarities with this chart. First is that there is no definition in ISO 12647 of what printing condition the letters "A" through "H" represent.** ISO 12647 does not clearly state whether these dot gain curves are intended to be tone reproduction targets or aim points or simply what you get when you use linear film to make printing plates. It appears that, because the specifications state that "direct analogies to film production systems are maintained" the intent is to use these curves as the reproduction targets. To, me, the idea of having different tone reproduction curve targets for presswork for different processes or different halftone line screens is counterproductive to standardization.

Resources:

Data set/s for profiling, separation, and proofing
ECI www.eci.org Profiles based on FOGRA data sets
FOGRA www.fogra.org Data sets that closely comply with ISO 12647
GRACoL http://www.idealliance.org
IFRA www.wan-ifra.org Profiles based on ISO 12647-3 (Newsprint)
SNAP www.naa.org SNAP profile
SWOP http://www.idealliance.org

Part 1 on this topic can be viewed by clicking HERE

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*Standards documents include two broad classes of information: "normative" and "informative"
Normative elements are defined as "elements that describe the scope of the document, and which set out provisions". Provisions include requirements that convey criteria to be fulfilled if compliance with the document is to be claimed and from which no deviation is permitted.

Informative elements include supplemental information such as additional guidance, supplemental recommendations, tutorials, commentary as well as background, history, development, and relationship with other elements. Informative data is not a requirement for compliance with the standard.

**As near as I can guess (so I may be wrong), here are the printing conditions represented by the letters "A" through "H" in the ISO dot gain chart. The curves are organized from the bottom up. They sometimes do double duty.

So:

A is the curve for CMY for Coated positive plate (ISO Coated v2 and FOGRA 27, FOGRA 39 etc)
B is the curve for K for same above condition

B is also curve for CMY for Web (paper type 3)
C is the curve for K for uncoated

C is also the curve for CMY for paper type 4/5 (uncoated and uncoated yellowish)
D is curve for K for same above condition

F is the CMYK curve for 20 micron non-periodic/FM screening

E, G and H are unknown (by me anyway). I believe that "H" has been dropped from the latest ISO 12647 document so these may no longer be in force.

Technical tips for creating brand colors

Color is one of the most critical components in creating brand identity and while there is a fair amount of information on the psychological and cultural aspects of color - there's very little information on the technical issues that need to be considered when developing a custom or brand color.

Brand colors are custom (a.k.a. line, spot) colors that are any single color (typically other than cyan, magenta, yellow, or black) that are usually printed as a solid area of ink on a dedicated press unit.

There are two types of custom colors -
1 Proprietary
2 Referenced.

Proprietary custom colors are colors that are created by the brand owner or their creatives. Coca-Cola red and Kodak yellow are examples of proprietary brand colors.
Referenced custom colors are usually published in color palettes that are to be used by creatives to specify spot colors.

The main brands of referenced custom color palettes are:

Pantone, the dominant spot color printing system in the United States and Europe.
Toyo, a custom spot color system that is popular in Japan.DIC, Dainippon Ink & Chemicals, Inc., another popular Japanese custom color system.
ANPA a palette of 300 colors specified by the American Newspaper Publishers Association for spot color usage in newspapers.
HKS Hostmann-Steinberg Druckfarben, Kast + Ehinger Druckfarben und H. Schmincke & Co. a custom color system containing 120 spot colors and 3250 tones for coated and uncoated paper.
The main benefit of creating a proprietary brand color is that it is unique to the brand thereby enhancing the brand's unique identity. The downside is that the creatives/brand owner are required to create their own system of specifying, communicating, and manufacturing the color.

The main benefit of using colors from a reference custom color palette is that the system of specifying, communicating, and manufacturing the color has already been built. The downside is that the color is not unique to the brand and can be used by others, potentially creating confusion in the marketplace.

When creating a new proprietary custom colors to be used for brand identity keep these technical tips in mind:

1- Humans have very good color discrimination for greens and much less for blues, reds, yellows, and purples.This means that they can more easily distinguish between subtle differences in two similar greens than they can two similar reds. It also means that there are more green custom color options than there are red.

2- In offset lithography, the range of possible greens is larger than that of reds, blues, and oranges

3- Humans have poor color discrimination when hues are very saturated - I.e. saturated colors will tolerate greater variation in reproduction before a color shift is noticed.

4- RGB, CMYK, and Hexadecimal values do not actually define colors because those values are device dependent. I.e. it does not, for example, tell us the specific hue of the Cyan ink being used - a factor that will change depending on the ink manufacturer.A demonstration by Flint ink of the influence on ink color resulting from differences in the substrate upon which the ink is printed.
So, a color defined using CMYK values will also look like a different color when printed on newsprint, in a magazine, or in a brochure due to the differences in the specific CMYK inks used and the substrates they are printed on.
Instead, define the color using CIEL*a*b* reference values since these are device independent. If RGB and/or CMYK values must be provided then make sure that the version or source is included (e.g. sRGB, Adobe 1998 RGB, CMYK/SWOP, CMYK GRACoL 7, etc.) to help minimize variation.

5- Confirm that the proposed custom color is within the color gamut of the expected most used reproduction process.An application like Chromix ColorThink enables the CIEL*a*b* values of the custom color to be compared with the color gamut of the system that will be used to print it and determine if it is reproducible or not - i.e. in, or out of, gamut.
If the custom color is within gamut, it means that it can be simulated by mixing screen tint percentages of the primary inks of the print process.

6- Make sure, by testing, that the ink pigments used in the custom color will not shift hue because of heat e.g. during lamination or react with other inks or to oxygen e.g. Reflex Blue.

7- Avoid using fluorescing agents in the ink.

8- Use certified sample color swatches and CIE L*a*b* values to communicate color globally.Ideally the sample swatches should be as large as possible since the perception of color changes with coverage area. Also include a "Hi-Lo" reference which shows how much darker or lighter the color can be and still be in specification. If possible, include a CIEL*a*b* Delta E value for how far the hue of the color can deviate while still being within specification. Include the information about how the Delta E value is to be calculated (e.g. Delta E 98, Delta E 76, Delta E CMC, etc.)

9- Prevent brand bloat by consolidating/rationalizing custom color libraries. Retire old colors and consolidate colors that are very similar.

Addendum
A number of readers questioned my statement that humans have very good color discrimination for greens and less so for other colors. In the below video Eric Fossum, image sensor engineer and primary inventor of the CMOS sensor used in digital cameras, mentions the color sensitivity of the human eye during a recent talk at Yale University.

Ghosting

A printing "ghost" is an unwanted image resulting from the printing system itself. There are basically two kinds: mechanical and chemical.

Mechanical ghosts are usually visible as soon as the press sheet lands in the delivery section of the press. There are three types of mechanical ghosts: starvation, blanket, and plate.

Starvation ghosts

A "light print ghost" appears in large solid or dark halftones either as a light or dark image of another part of the press form. It is caused by the layout of the press sheet elements combined with the limitations of the press inking system.Light print starvation ghost.
This can happen when graphic elements contact the form rollers on the press just ahead of large areas of heavy solid ink coverage. The graphic elements remove more ink from the form roller than the press can make up before these rollers come in contact with the solid. As a result the solid receives less ink in those areas and the graphic elements appear as a light image in the solid.

Strategies to avoid this problem include: rotating or "cocking" the press form relative to the press sheet so that the graphic elements are no longer in the same inking zones, changing the imposition or design to eliminate the problem, running the job on a larger press with greater inking capacity, making sure that water levels are run at a minimum, running on a larger press sheet and adding "take-off" bars - graphic elements - in the non-live image area of the sheet to even out ink usage.

A "dark print ghost" occurs when knocked out graphic elements immediately precede an area of heavy ink coverage.Dark print starvation ghost.
This is the opposite of a light print ghost. Here, the knock out can cause excess ink to remain on rollers in the reverses causing a dark image of the graphic to appear in the large solid.

The same strategies used to avoid a light print ghost are also used to avoid a dark print ghost.

A "plate ghost" or a "blanket ghost" appears when graphic elements intrude into the printing as latent images.Plate/blanket ghost.
This problem usually occurs on multicolor presses where the press form on one of the color units sensitizes the plate of the following color unit. Proper desensitizing of the affected plate and ink adjustments should correct the problem, however, sometimes the plate and/or blanket may need to be replaced.

Comment below submitted by "Otherthoughts"

For what it's worth? The how, why and when that I've used ink take-off bars in the past.

Solid ink Borders were the most prone to a starvation type of mechanical (ghosting?) in my experience, especially PMS spot color borders.

In my sheetfed experience, often there was a bit of space available for ink take-off bars, our standard sheet size was 19" x 25". Despite there being some space available, ink take-off bars were never used to make a job easier running and nicer looking as a matter of course by anyone other than myself. I employed them as a stripper because I knew that the pressman would appreciate the help (being a former pressman myself), and because I knew it would produce a better printed result.

The type of job that really needs them, doesn't come along all that often, here's an example.

Lets say the form below shows a reflex blue to be run as a fifth color. And lets say that the reflex blue borders will trim out to be 1/2" wide on all four edges.Without ink take-off bars, ink usage ranges from 17.125" to 2.125", a ratio of 8 to 1
With ink take-off bars, ink usage ranges from 17.125" to 3.562", a ratio of 4.8 to 1

Layout Details
Limited the bleed at both the gripper and tail to 1/16" each. Butted the pages together at the circumferential center line mark and finally shrunk the Color-bar down to 1/8". This leaves 1 7/16" to implement the take-off bars on a 19" x 25" sheet.

Gripper margin = 00.312
8.5 x 11 x 2 = 17.000
Bleeds x 2 = 00.125
Color bar = 00.125
Total = 17.562

Notes As you well know, ink take-off bars are useful with low total ink coverage scenarios as well, but such scenarios have nothing to do with ghosting/starvation. Regardless, prepress failed to employ ink take-off bars in this scenario just as well. If there was no room for ink take-off bars on a job, we did without them, which was essentially "No Change" from what we did in all cases. :)

Gordo's response

The iconic National Geographic magazine cover border is a great example of this problem - but uses a different solution. They don't have enough space on the press form to add ink take-off bars, so instead, in anticipation of the increase in darkness at the top and bottom of the picture window, they use a screen tint of the solid spot color in those sections of the border.Left: as the cover would print with a solid spot yellow border. Right: as the cover prints with the top and bottom sections of the spot yellow halftone screened.
The screened part of the spot yellow bar gets darker on press due to the mechanical ghosting effect and ends up the same color as the solid yellow on either side.

Chemical ghosts are related to the chemical activity of inks as they go through their normal drying process. Their appearance is usually unpredictable and, unfortunately, become evident only after the job has been printed and in the press delivery pile for a period of time.

Chemical ghosts may appear as reproductions of one side, or part of a press form, in the solid area of another part. Their appearance can be erratic - showing up in one area of the printed sheet but not in a similar or duplicate part. They usually appear as a dull ghost on a glossy background or as a glossy ghost on a duller background.

What makes an ink glossy or dull.

When an ink appears glossy, it is the result of enough ink vehicle forming a film on the surface of the paper to provide a smooth covering layer for the pigment particles in the ink.Graphic representation of the edge of a sheet of paper showing ink pigment particles suspended in the ink vehicle.
When an ink appears dull, it is the result of the ink vehicle draining from the surface into the paper so that the irregularities of the individual pigment particles and paper surface are not covered with a thick enough film of ink vehicle to create a gloss appearance.

How inks dry

When ink is printed on a press it goes through two distinct phases:

1 - Setting - the drainage and leveling of the ink vehicle into the paper coating or fibers. This causes the ink to "gel" and become immobilized.

2 - Oxidation - the polymerization of the ink vehicle into a solid mass creating a hard film.

As the film of ink oxidizes it releases gaseous by-products. As a result, the ink printed on the second side of the press sheet can be exposed to the gaseous by-products from the oxidation of the first side if it is printed at a critical point in the first side's ink drying cycle. Those gasses affect the drying rate of the second side ink selectively as the sheets are stacked in the press's delivery. This results in an ink film that has been immobilized at two very different rates, and therefore has areas of high or low gloss which reflect the image on the other side.Graphic representation of sheets of paper in the delivery of the press showing gaseous by-products released as the ink dries.

Rich black - the problem of black in presswork

Like all process color inks, the black ink that is used in 4/C printing is transparent. As such it cannot cover ink, or black out the paper, as thoroughly as one might hope. Instead, black ink by itself actually appears to the eye as ranging from an apparent black when it's used to cover very small areas to just a dark grey when it covers large areas.Even though it appears greyer, the box on the right is the same printed 100% black as the text on the right.
The solution to the problem of grey blacks is to boost blackness by printing other inks under the black ink. This effectively darkens the brightness of the paper over which the black ink will be applied thus making the black "blacker."

Blacker black strategies

There are several ways to making a black blacker:

1) Apply a screen tint of a process color - magenta or cyan down before the black.

2) Apply a mix of process colors - cyan, magenta, and yellow down before the black.

3) Apply two hits of black ink.

The first option is sometimes called a "rich" black, while the second is called a "super" black, and the third a "double black."

With a Rich black the other process ink is usually a 60% tone of cyan. This causes the black to appear “blacker” because the second ink color increases its density. It also makes the black "bluer" which adds to the darker appearance. A 60% magenta could be used instead of cyan to impart a warmer appearing black.Left: 100K/60M. Center: 100K. Right: 100K/60C.
Rich blacks are typically used whenever the image is larger than 1 square inch and smaller than about 9 square inches in area.

A Super black, where 3 process colors underlie the black, is typically used when the black area is larger than about 9 square inches in area. The typical screen percentages are: 50% cyan, 40% magenta, 40% yellow, and 100% black.Left: 100K. Right: 100K/50C/40M/40Y.
In contrast to using a single process color, this screen tint combination preserves the neutral appearance of the black. This screen ink combination also means that the maximum amount of ink in the black amounts to just 230% coverage which should not cause any on-press issues like excessive drying times.

Unfortunately a Super black can be problematic on press because it is used for large black areas while at the same time using the same inks that are used for the color-critical image areas. That can cause a conflict on press if ink densities need to be adjusted to align the image colors with the proof while keeping the Super black neutral and at the correct density. To solve that problem, printers may opt to use two hits of black ink. The first black ink is tied to the CMY of the images, while the second black is independent of the image. That allows the press operator to adjust the CMYK inks as necessary to get good color on the images with the second black ink only being applied where a large area of black is needed. The downside to this strategy is that it turns a 4/C job into a 5/C job (CMYKK) which may increase production costs.

The black booby trap

On a computer monitor, there is only one way to represent black - the screen is black when there is no light coming from the display. So a 100% black, a Rich black, a Super black, and two hits of black will all appear the same on screen.A 100% black bar, a Rich black bar, a Super black or, two hits of black ink all appear the same on screen.
100% black bar as it appears in print if it is set to "knock out" of the background image.
100% black bar as it appears in print if it is set to overprint the background image.
A Rich black bar - 100%K/60C as it appears in print. The 60% C not only serves to darken the black but it also knocks out the background image which eliminates any "ghost" images caused when black simply overprints a background image.
Because the on-screen appearance of the black may appear the same despite being made up of different screen tint combinations it is critical that the Rich, or Super black be clearly identified as such in the custom color menus of page layout and illustration applications. Create the color and name it according to its function and make up. E.g. Black for standard process black, "RichBlack 100K60C" and "SuperBlack 100K50C40M40Y"