Friday, February 24, 2012

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

Tuesday, February 14, 2012

Understanding paper brightness and whiteness

For most printers and print buyers, the terms brightness and whiteness are interchangeable. However, when describing the characteristics of paper there are some important differences between the two terms.

Brightness refers to the percent reflectance of blue light, as measured at a wavelength at, or about, 457nm. The choice of that wavelength is based on the sensitivity of the human eye to blue and yellow light. Brightness was originally a test in paper manufacturing to measure the effectiveness of the bleaching process in removing yellowness from pulp. When paper is bleached, the spectral reflectance curve increases the most in the blue and violet range, at about the 457nm point. This has also made the measurement of brightness well suited for measuring the aging of paper because paper yellows with age. Most white papers are in the 60 to 90% brightness range.
Paper brightness requirements for ISO 12647-2. Currently there are no specifications for ISO 12647-3 (newsprint), ISO 12647-4 (gravure), ISO 12647-5 (screen printing), or ISO 12647-6 (flexo).

Whiteness, on the other hand, refers to the extent to which paper reflects equally the light of all wavelengths throughout the visible spectrum. A truly white sheet of paper will not absorb one wavelength of light energy more than another. For example, if a sheet of paper is placed under a full spectrum light, most of that light will be reflected back equally and the paper will appear white. However, if some of the wavelengths of light energy are absorbed, the color of the paper will shift to the light which was not absorbed, but was instead reflected back to the viewer. That is why a red sheet of paper appears red in white light because it absorbs all the other colors and reflects only the red.

In the draft of the new ISO 12647-3 there is a value of 58% for paper brightness specified. The paper whiteness is "To be defined by the paper suppliers".

Saturday, February 11, 2012

Some idle time on the interweb

I recently spent a bit of time wandering aimlessly on the interweb, just following links to see where they'd take me. The web is really amazing - we sometimes take for granted how lucky we are to have it at our disposal.

A printer's invoice from 1936 showed up for sale on eBay:W.E. Baxter was a printshop located in Lewes, Sussex, England - the town where I lived when I was a little boy.

The invoice is made out to a Miss. Bradley and a bit more searching on the internet turned up this photograph of the young lady:
It appears the Baxters had ink in their veins. George Baxter (born July 31, 1804, Lewes, Sussex - died Jan. 11, 1867, Sydenham, Kent) was an engraver and printer who invented a process (patented 1835) of color printing that made reproductions of paintings available on a mass scale. He was the son of John Baxter (1781–1858), printer and publisher at Lewes, who issued the popular illustrated “Baxter” Bible.
The building in Lewes where they did their work is identified by this beautiful sign painted directly on the building wall:
And for those of us not fortunate enough to be able to visit the building in person, Google's Streetview provides a lovely vantage point with the W.E. Baxter building on the right center of the view:
Today the W.E. Baxter building houses rental accommodation rather than printing presses. The commercial print operation of W.E. Baxter moved from Lewes to a property in South London in 2002 but continued to experience losses. It was moved again in May 2004 to the nearby premises of Pegasus Colourprint where, as far as I can determine, it remains today.

Friday, February 3, 2012

Who is responsible for print shop color?

In basic terms:

It is management's responsibility (with input from prepress, press room, and sales) to establish what the presswork color targets and tolerances (dot gains, standards, specifications etc.) are for the presswork - because those are marketing/business decisions. Then provide the tools (training, resources, equipment) to allow prepress and pressroom to achieve those targets.

The responsibility of prepress is to align proofing to the target established by management as well as to maintain proofing within the tolerances established by management because tolerance targets are also marketing/business decisions. Prepress must also output plates that enable the press operators to align their presswork to the proofs with the press performing in a repeatable, stable, cost-effective condition.

The responsibility of the press operator is to manage the press in such a way that the films of the appropriate inks are laid down in a manner that meets the targets and tolerances (hue, trapping, etc.) established by management and that the halftone dots on the plate are reproduced with fidelity on the various substrates (avoiding slur, doubling, etc.). Also, the press operator needs to make sure that all press-related consumables (fountain solution, inks, etc.) are within the tolerances needed to achieve the management defined targets for pressroom output.