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How to control color quality?

I have experienced very often that the products of trial or general production did not meet the expectations for the color. I even have experienced the complaint for two different parts which should be the same color, but somehow they were not. In the application were on different areas and the quality manager sat in the car and shouted that the parts are not the same color. What a eye! :)

Although color evaluation can be subjective and emotional, today's color measurement systems can help by removing any subjectivity from the process. Color management solutions give data-based analysis, so everyone who is a part of process from designers and specifiers to suppliers and manufacturers are speaking the same color language.

Take a look at the tips what can help you to manage your color quality control.

  1. Color must be quantified and measurable.

You cannot just say to a supplier that a specific part has to be bright green or have a touch more red. These are subjective color descriptions that create confusion and problems. But if your customer tells you to match his color standard within a tolerance of DL*1, DC*1 and DH*1, you can produce the color with confidence! Capturing color data using high quality, reliable color measurement instruments is a must here.

  1. You cannot count on a spectrophotometer alone.

For measurement you will need a calibrated spectrophotometer which captures the color data, then quality control software that you can use to analyze, track and communicate that color. You will also need a calibrated light booth for quality control. When you use these three tools together you can perform visual and instrumental evaluation and approval.

Calibrated light booth which offers consistent lighting conditions under which to evaluate color

 

  1. Viewing samples outside under ‘daylight’ does not comply with standard D65 lighting!

Natural daylight is dynamic. There is different light when is sunny and cloudy, when you evaluate color at 10 a.m. and then at 4 p.m. Each time the color will look different. The benefit of a calibrated light booth is that it offers consistent lighting conditions under which to evaluate color. Controlled, standards-compliant lighting lets you make confident decisions, quickly and easily evaluating whether color is right.

  1. Use the right Delta E tolerancing model

Did you know that there are many types of Delta E tolerancing models, and several of them are obsolete? Some companies are still utilizing the older tolerancing models without even realizing it. Spherical tolerancing, such as the original Hunter Delta E, CIE DeltaE*, and others are static and don’t work visually in some areas of color space. Of course, change is difficult and expensive. If you are using an outdated spherical tolerance model and are having high rates of customer rejects, this should be the right time to start the communication with management about updating your tolerance model.

  1. Different people speak different color languages.

Some colorists speak Munsell’s language of L*C*h while others speak the L*a*b dialect of industrial science. Both are methods for calculating color. L*C*h° focuses on lightness, chroma and hue, but that information may not have the same meaning. This is where color management software can help by doing the L*C*h° to L*a*b* conversion for you. 

 

Here both methods of color specification are shown. Keep in mind that the area outside of the perception ellipse is still recorded as “good” by the software. This is a color that would pass inspection instrumentally, yet be visually poor to a trained eye.

  1. All tools must be set to the same conditions.

Creating standard operating procedures that clearly define what conditions to use when measuring samples and sharing them across production lines, facilities and suppliers will help ensure everyone is following the same process for measuring color accuracy.

  1. You don't know what you don't know.

There are many options of educational opportunities from national seminars to convenient online courses and custom training designed to meet your specific needs. As with any field, it's important to stay up to date on the latest trends, best practices and technology.

 

Author: Jana Loskotova