Ed #1 Metallics

General Characteristics of Metallic Inks

Particles make it shine.

Ink manufacturers create metallic inks by starting with a pigment that is close in color to the desired metal and adding small metallic particles to it. To regulate cost, bronze, aluminum, copper and zinc are commonly used. Actual gold and silver are rarely used due to expense. Some metallic inks are more expensive than others, reflecting the quality and research behind them.

Because of their particulate nature, metallic inks, unlike process inks, are opaque. In order for these inks to work on an offset press, the particle size can be no larger that 25µm (microns) or about a thousandth of an inch. The irony here is the smaller the particle, the less shiny the final effect. Refer to the note on “liquid inks” to find out how to get bigger particles, thus more shininess, on an offset press. In addition to being opaque, metallic inks require a different ink/water balance than conventional inks, thereby making them more difficult to work with on-press. Because of its particular metallic nature, neutral color balance and high reflectivity, silver is the easiest and most popular metallic to work with.

These particles float to the surface during drying.

Leafing is the special characteristic of metallic inks where metallic particles float or “leaf” to the surface, giving the ink a metallic luster. Longer drying times enhance this process. If the ink dries too quickly, such as with ultraviolet inks, leafing will be shortchanged, cutting back on the metallic effect. Leafing is, however, a two-sided coin. The downside is that when these metallic particles leaf and rest on the surface, they make the dried ink more vulnerable to rub-off. Which brings us to coatings.

Metallics benefit from protective coatings.

When metallic inks are used over large areas, varnishing or aqueous coating is recommended to protect them from scratching and smudging. Any protective coatings will soften the luster to some degree. Dry trapping the coatings (applying them after the ink completely dries) will minimize this softening. Certain coatings, such as film laminate, may have difficulty adhering to the metallic due to its particulate nature and should be tested before production. Different effects can be achieved by combining different varnishes. (See example “two color kiss fit”)

Coated gloss paper enhances metallic sheen.

The printing substrate has a profound effect on just how metallic this type of ink will look. The basic rule of thumb is the harder and less porous a surface, the more reflective the metallic ink will appear. Based on this, coated paper works better than uncoated. Furthermore, gloss coated is better than dull or matte coated paper. Premium gloss coated paper with superior print gloss will yield the best results. When printing metallics on matte or uncoated surfaces over large areas, it is often necessary to use two hits of the ink to achieve a smooth appearance.

“Liquid” metallics provide more shine.

This relatively new form of metallic ink provides a significantly higher level of sheen than paste inks. This is because they are water-based and capable of carrying a larger metallic particle size. Liquid inks tend to be more costly and, in most cases, require a coating tower for application (such as those used for aqueous coating). As with aqueous coatings, they are limited to large solid areas or shapes and cannot be used in small typography or halftone dots.

Pearlescent inks offer an alternative.

Some pearlescent inks create the illusion of a metallic finish, but with certain advantages over metallics. Most importantly, they are not as opaque so they can easily be applied on top of other colors. These pearlescent inks are comparable in price to high-end metallics and considerably more expensive than conventional transparent inks. (see example, “first-down touchplate”)

Screening metallic inks can diminish luster.

The larger the surface area of metallic, the more chance it has to shine. It therefore stands to reason that when metallic ink is applied to an area as small as a halftone dot, the shine will not be as apparent. If the dot is small enough, say less than 30%, it may simply appear as a non-metallic color. Because of this principle, metallics lose much of their luster in the highlights and quartertones, when applied to halftone photographs. (see example, “wet trap duotones”)

Reversing type and rules requires more care.

The logical way to print a large area of metallic is to run the ink heavier, enhancing the shininess. However, if small typography or thin rules are reversing from that same metallic area, it may be difficult to maintain a clean reverse. The particulate nature of metallics and their unique ink/ water balance make them print “thicker,” restricting their ability to maintain as fine a reverse as conventional ink.

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