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