Ed #1 Metallics

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.

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.

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.

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.

Creating custom metallic color through ink mixing.
Virtually any custom color can be given a metallic sheen through ink mixing. Typically, a balanced metallic silver finished ink is used as the carrier or base for mixing metallic colors. The ratio of base-to-color will vary depending on the strength of the color and the amount of sheen desired. Since silver ink has a gray value of 30%, it will darken the custom color in the mixing process. Also, mixing regular inks with metallics reduces their opacity. Request ink samplings or draw-downs prior to finalizing the formula and color.

Overprinting color on metallics.
Any type of custom color or four-color process, whether it’s color-separated halftones, multi-tones or screen/tint builds, can be printed directly on top of metallic inks. Keep these basic rules in mind:

– Print the metallic first.
– Letting it dry (dry trapping) before overprinting colors is not necessary but will yield more reflectivity.
­– Silver is the standard choice for overprinting because of its strength and neutrality.
– Standard silver has a gray value of about 30%, so it will darken what’s printed on top of it. Color separations and screen/ tints should be adjusted accordingly.
– Lighter screen values, from 30% down, allow more metallic to show through. As the screen value increases, the metallic quality is lessened. Because most color inks are transparent (except fluorescent), they will allow some metallic to show through even in solid form.

In some cases, a metallic can be printed on top of other colors for a different effect.

Incorporating metallics into color separated images
True duotones are created by printing a black halftone on top of a metallic halftone. Dry trapping is recommended to increase the luster of the metallic. In addition, the tonal range of each halftone can be altered in favor of the metallic to let it dominate in the highlights and mid-tones. The metallic should be minimized in the shadows because it has a tendency to turn the black gray.

Fake duotones, where a black halftone is printed over a solid area of metallic, yields a more dramatic effect since all of the whites and highlights in the photo will actually be metallic.

Touchplates utilize an existing color unit, such as the black, and repeats it with a metallic, such as silver, for further enhancement.

Five- or six-color separations actually integrate the metallic color into the four-color separation. This technique renders true metallic sheen in exactly the areas and densities where they are most required.

Process color substitution is achieved by using a standard four-color separation and substituting one of the process colors with a metallic color. The most common and effective example of this is substituting process yellow with metallic gold. Any variation is possible however, including substituting a process color with a mixed-ink metallic version of that same color.

There are other ways to achieve striking metallic effects besides using metallic inks. Some of these include foil stamping (see Ed #5).