Question:
Why do some ink colors, such as Reflex Blue, take longer to dry and require aqueous coating?

Answer:
Variables in ink drying time are too numerous to delve into too deeply, but they include the paper conditions, relative humidity and temperature in the press room and many others. But you have a good point. Some inks are indeed harder to get to dry than others, and reflex blue is one of them. For example, Yupo (makers of synthetic printing papers) lists Reflex Blue as an ink to avoid when printing on their substrates. The basic reason is ink chemistry and certain inks require additives that hurt drying time. Metallic inks and florescent inks are also notorious for taking a long time to dry. Ink chemists have come a long way in perfecting fast drying inks, but the science can come at a cost. “Fast drying” inks are often more expensive. In any case, not every ink manufacturer’s “Reflex Blue” has the same chemical make-up, so drying times can vary.

An aqueous coating can “seal” the ink preventing it from rubbing, and presses that lay down the coating also have built-in dryers for the coater, However, this does not mean you must use an aqueous coating because you want to run Reflex blue. Careful selection of papers and the use of a dryer on press can get your job printed without a special coating.

Also remember that ink coverage has a great effect on drying time. The more ink you put on a sheet, the longer it will take to dry. If you are laying down a big solid, putting the aqueous coating, and/or printing with two hits of ink (sometimes the first hit is a solid and the second is a screen of the same color) can improve the final appearance.

Stephen Beals is a digital pre-press manager and has been writing for major print publications for many years. He is the author of A Practical Primer for Painless Print Production. He can be reached at stephenbeals@mac.com.
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