What Should You Know About Metallic Inks?
First of all, what is metallic ink? It is essentially varnish (a vehicle) with flecks of real metal (such as aluminum or bronze) suspended in the liquid. As the liquid dries, the metal flecks rise to the surface and begin to reflect the surrounding light.
Metallic inks, unfortunately, are far more susceptible to rub-off than conventional inks. (That is, you can accidentally scrape off the ink with a fingernail or just by rubbing part of the brochure or flyer, or whatever, against another part of the printed sheet.) Therefore, to maximize rub-resistance, it is prudent to choose a coated or smooth uncoated--rather than rough uncoated--paper substrate. You may also want to varnish the printed sheet for protection. (You would do this after the press sheets have dried.) This presents its own problems, however, since over-printed varnish can dull the metallic sheen. To minimize this, your printer may choose to add back a little metallic ink into the varnish to maintain the ink’s reflectivity. (Unfortunately, although this will accentuate the metallic sheen, it may dull down the other, non-metallic inks on the press sheet. So it’s a bit of a trade-off.)
As with any rule, there are always exceptions. Sometimes you will need to print metallic ink on a textured, uncoated press sheet for design reasons. In this case, to minimize rub-off, ask your printer about running a thicker film of metallic ink, or perhaps even a second hit of the ink printed after the first one has dried.
The key to success with metallic inks is “dry-trapping,” which means that your printer will lay down the metallic ink in the first pass and then let the press sheets dry completely before printing the other inks or varnishes in a second pass.
There are options: Laying down a flat metallic ink (or even a metallic halftone) and then dry-trapping other non-metallic colors on top of it is not your only option. Ink manufacturers and printers are now mixing quantities of metallic inks directly into spot colors, or even into process colors, to create new and different hues. In fact, any color can be transformed into a metallic by adding metallic paste to it. (The color will just no longer be the same hue as the original PMS or process ink.)
Another option is a procss called MetalFx, which first lays down metallic
silver and then overprints the metallic with cyan, magenta, yellow, and black
inks. This patented process (similar to the dry-trapping noted above, but
without the wait) allows the printer to match a wide range of metallic colors
due to the transparency of the process inks and the show-through of the metallic
ink below. Be aware, however, that this is a proprietary technique for which not
all printers have received training.e
The good news is that in this operation, the process inks behave like a varnish to protect the metallic ink base and keep it from scuffing. In addition, the final effect is opaque enough not to require two hits of the metallic ink. In fact, the entire process can be completed in one pass on a five-color press.
What should you do if your printer thinks the metallic ink will lose its shine completely on the paper you've chosen?
There are always options. If your metallic silver ink stands a chance of looking grey on the rough, uncoated sheet you have chosen for your project, you can always choose foil stamping instead of ink. The foil will sit up on top of the paper completely. Since it is not an ink, the foil will not be absorbed into the paper at all and will maintain its shine on any substrate.
Nevertheless, you will pay a price for this. The printer will need to create a stamping die and then affix the metallic foil to the press sheet with heat and pressure using a letterpress instead of an offset press. Some printers will have to subcontract this work out, which will also add to the cost and turn-around time of your job.
To achieve your printing goals while saving money, talk with your printer early in the process to determine the most economical--and most appropriate--printing technology for producing metallic effects.
New directions: This entire arena of metallic printing has been undergoing dramatic changes recently, with liquid foils, inks that aren’t absorbed into the paper, and other unique options coming onto the market under various trade names. Some metallic ink processes even include UV inks, eliminating the need to wait before printing a second pass, since the “curing” (drying) of UV inks under ultraviolet light is instantaneous.
In short, whenever your design piece involves metallic effects, the most sensible approach is to give your offset print provider actual samples showing what you want to achieve. This will help him determine the best avenue for success.
One final caveat: Here’s one final piece of information that may help you avoid nasty surprises: If the printed piece will need to be fed into a laser printer (or another high-heat digital press) after being printed, tell your printer early. Metallic inks need to be formulated in such a way that they will not melt and streak in your laser printer. Properly prepared metallic offset printing ink will protect the laser printer rollers as well as the metallic printed pieces themselves.
[Steven Waxman is a printing consultant. He teaches corporations how to save money buying printing, brokers printing services, and teaches prepress techniques. Steven has been in the printing industry for thirty-three years working as a writer, editor, print buyer, photographer, graphic designer, art director, and production manager.]