Reflective surfaces and metallic inks are very popular for printing and packaging applications. Consumers love the look; but for printers, these substrates and inks are expensive and make color control a challenge.
Today we’re taking a look at the measurement options available for controlling these very marketable print and packaging applications to help printers and converters meet brand owner expectations and maintain the highest possible quality output.
Sphere vs. 0/45°… what’s the difference?
There are two primary types of spectrophotometers used in the printing and packaging industries today – the traditional 0/45° (aka 45°/0°), and the spherical (aka diffuse/8°).
With a 0/45° spectrophotometer, the first number refers to the angle of illumination and the second to the viewing angle. The light source shines at 45 degrees from the surface of the sample being measured, and the detector receives reflected light at 0 degrees, perpendicular to the object’s surface.
A sphere spectrophotometer, on the other hand, illuminates the object diffusely from all directions, and the detector receives the reflected light at an 8 degree angle from the object’s surface. Spherical in shape, these instruments are lined with a highly reflective, very low gloss, white matte surface. As the light beam strikes the surface of the sphere, more than 99% of the light is reflected and scattered randomly in all directions.
These diagrams show the difference in measurement geometry between 0/45° and sphere spectrophotometers.
When to use each
A 0/45°, like the X-Rite eXact, not only considers color, but also gloss and texture. Because they perceive color in the same way as the human eye, 0/45° spectrophotometers have been historically popular for measuring color on smooth or matte surfaces in printing and packaging operations. But with the growing use of mirror-like and reflective surfaces, they may not always be the first choice for all applications. That’s because with glossy surfaces like flexible packaging, cans or metallic labels, colors will appear darker and more saturated than the same color produced with a matte finish.
With a sphere spectrophotometer like the Ci64, users have the choice of including (specular included or SPIN) or excluding (specular excluded or SPEX) the gloss component of an object’s surface. This is why sphere spectrophotometers are preferred for applications like shiny or mirror-like surfaces, printing over foil, and other highly glossy surfaces. Check out our SPIN vs. SPEX blog to learn more.
Since the mirroring effect of a metallic substrate is reflected by the coated sphere, there is an adequate amount of light for the sensor to measure. These measurements are similar to what the human eye would see when looking at the printed image on an aluminum can, metal bottle cap or metallized package.
Many printers are using metallic inks and substrates to enhance graphics and brands. They come in a variety of types and are composed of various pigments and metals. While a 0/45° spectro may be adequate for some applications, a sphere spectro is most effective for measuring the color of these materials.
So… which instrument should you choose?
If you’re seeing an increased demand to print products with translucent inks on foil or other mirror-like surfaces, or if you’re using metallic inks, you will be challenged to ensure brand and other colors are produced accurately if you don’t have the right instrument. A sphere spectrophotometer from the Ci6x family is probably the best choice in these situations.
For jobs that don’t use metallic inks or metallic surfaces, a 0/45° like the X-Rite eXact might be best for your needs. While it is feasible to measure inks on foil or metal using a 0/45° spectrophotometer, you need to understand that technology limitations may provide measurements that show the sample as darker and more saturated than it really is.
To determine the best instruments for your applications, you must analyze job mix and customer requirements to determine if your critical measurements can be made with one type or the other, or whether it makes more sense to have both instruments available in your facility. If you’re still not sure, our experienced Color Experts are available to help you determine the best solution for your workflow.
If you’ve established a good workflow for your paper-based products, but metallized substrates are throwing you for a loop, check out our Effective Color Control on Metallized Substrates blog or on-demand webinar for help.