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.
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