Learn what ink density is and why it is important to adjust the density curve of a profile.
In past articles, I cautioned that you should limit ink densities to no greater than 250% to 275%. One reason, is that the volume of ink that you print on a substrate has a direct effect on the dimensional stability of the film that you are printing on. The more ink that you lay down, the more contraction of the vinyl you can expect as the ink dries. When this happens, the applied graphic can peel at the edges. Even before the film is applied, the vinyl can start to curl at its edges on the release liner. Failure to limit ink density can also lead to other problems, which I will expound upon shortly.
What is Ink Density?
What I would first like to do is to define the term “ink density”. Let’s start with your four primary ink channels: cyan, magenta, yellow and black (CMYK). If you print the maximum amount of each ink, you get 100% of cyan + 100% of magenta +100% of yellow +100% of black. Add all of these percentages together and you get 400% ink density.
Why is Ink Density Important?
That’s a lot of ink. About 90% of which is solvent. That’s why, when you print a heavy concentration of ink (over 250% to 275%), the solvents can chemically attack the vinyl facestock and can actually penetrate the film and compromise the bond of the adhesive to the substrate. Some films are more prone to shrinkage and edge curl than others. To overcome or compensate for these problems, never print to the edge of the media. Instead, provide a 1/4-in. ( 6mm), outline around the printed image.
Heavy
ink concentrations can cause other problems. When you print more ink than the
media can handle, the individual dots start to spread and blend together with
adjoining dots. The ink can also bleed or puddle into ink islands. When this
happens, colors become muddy. As the ink spreads, you also lose detail and
crisp edges.
Other
issues include banding and excessive drying time. And, by virtue of the fact that you have added
more solvent onto the surface of media, it naturally takes longer for that
solvent to dry. Even when you maintain the total ink limit
within the recommended range, it can take at least 24 hours for the print to
adequately dry, before you can laminate the print.
To
minimize bleeding, slow your printing speed. The slower speed also reduces the
likelihood of vinyl contraction, because the ink has extra time to start drying before another ink layer is printed.
The downside is, of course, less printing efficiency.
To
accelerate the drying of the inks, you may be tempted to increase the dryer
temperatures. Easy does it! During heating, the expanding film can tunnel on
the release liner. Tunnels between the film and release liner can form as the
heated film under the dryer expands and pushes against a cooler, rigid, film
mass.
Adjusting the Density Curve.
When printing higher resolutions, in addition to adjusting the density curve in your profile to control the amount of ink that you print, reduce your print speed. You'll experience less bleeding, especially when printing onto glossy films. You also give the ink more time to dry before the printheads make another pass. Generally, you get better results with matte-finish films, as opposed to glossy ones.
If
you are printing on a dark film, such as RTape’s slate grey ChalkTalk®
chalkboard film, you should print a white mask first, then print your process
colors. Remember that ecosolvent inks are transparent. Without white, the slate
grey of the ChalkTalk film will show through. With
a white background, you will be able to print lower percentages of CMY to
attain a more desirable color. When printing on ChalkTalk®, limit your ink
saturation to 250%.
Test, Don’t Guess.
To minimize problems, test and evaluate your media choice with your printer and inks, prior to production. Each ink is unique and will adhere to the various types of print media differently. Ecosolvent inks, which are alcohol based, are milder than the strong solvent inks and do not bite into the media so aggressively. The traditional solvent inks utilize a strong solvent, such as MEK, and adhere better to a broader range of substrates.
In
addition to the ink types, also be aware that each printer works a little
differently and consequently requires different adjustments, with respect to
ink limits, temperature settings and print speed. Settings will, of course, vary
from one media to another. Cast vinyls require different settings than
calendered vinyl films, and a polymeric vinyl will print differently than a monomeric vinyl film.
Vinyl Application Videos
Squeegee Technique. Nothing is more basic in vinyl application than the squeegee. But some squeegees work better than others. And there are right ways and wrong ways to use this simple tool. This video clip reviews squeegee selection, squeegee care and squeegee technique. Click to Link
Wet Applications. Dry applications are typically recommended for most vinyl applications. For those exceptions to the rule, this instructional video explains the right way to perform a wet application. Click to Link
Application of Window Graphics. Installing vinyl graphics on glass can be challenging, because the adhesive aggressively grabs onto this high energy surface. Repositioning graphics on window is generally difficult, if not impossible. This instructional video explains how to dry apply window graphics right the first time. It also describes the necessary steps required for surface preparation. Click to Link
Transferring Frosted Window Graphics Films. Because frosted window films are highly textured, transferring cut vinyl graphics can be problematic. This video provides direction in selection of the right application tape and how to apply these films quickly, easily and without problems. Click to Link
3-Step Surface Prep. This instructional video describes how to properly clean the surface of a vehicle before applying pressure sensitive vinyl graphics to a trailer or doing a full wrap of a car or van. This three step surface prep involves detergent washing, solvent cleaning and a final wipe down with IPA. Click to Link
Vinyl Application Over Rivets. Applying vinyl graphics on vehicle surfaces with rivets is challenging for most sign makers. Vinyl failures to these surfaces are all too common. This video demonstrates some tips and procedures, used by professional decal installers, which will make these demanding applications easier and more trouble-free. Click to Link
Vinyl Application to Corrugations. Learn how to apply vinyl graphics to corrugations in a relaxed state. Forcing films into the valleys of corrugations puts too much mechanical stress on the film. Sooner or later, the vinyl will lift or tent in valleys. Click to Link
Applying Air Egress Vinyls. Vinyl films with air egress release liners have almost eliminated bubbles and wrinkles from applied graphics. Air egress release liners with their highly textured surface structure are problematic. Not much will stick to these liners other than the vinyl film. At RTape our best premask solution for air egress liners is a special Conform® tape called 4761RLA. Click to Link
About Jim Hingst: After fourteen years as Business Development Manager at RTape, Jim Hingst retired. He was involved in many facets of the company’s business, including marketing, sales, product development and technical service.
Hingst began his career 42 years ago in the graphic arts field creating and producing advertising and promotional materials for a large test equipment manufacturer. Working for offset printers, large format screen printers, vinyl film manufacturers, and application tape companies, his experience included estimating, production planning, purchasing and production art, as well as sales and marketing. In his capacity as a salesman, Hingst was recognized with numerous sales achievement awards.
Drawing on his experience in production and as graphics installation subcontractor, Hingst provided the industry with practical advice, publishing more than 150 articles for publications, such as Signs Canada, SignCraft, Signs of the Times, Screen Printing, Sign and Digital Graphics and Sign Builder Illustrated. He also posted more than 325 stories on his blog (hingstssignpost.blogspot.com). In 2007 Hingst’s book, Vinyl Sign Techniques, was published. Vinyl Sign Techniques is available at sign supply distributors and at Amazon.
© 2016 Jim Hingst
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