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1/1/1999 | 5 MINUTE READ

Assuring Paint Color at Behr

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Spectrophotometer helps Behr monitor and control color consistency of its products . . .


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Nationally recognized corporate logos result from careful planning and hours of thought regarding the effective use of color. The colors used in these logos are important to manufacturers because of the impressions they make on customers; they are often trademarked and fiercely protected. Dull grays and greens may express a sense of foreboding. The use of gold denotes quality; yellow is considered to be stimulating; blue is restful; and red conveys excitement. Color combinations such as blue and white are considered to be best suited for business logos, while red and yellow mixtures are favored by fast food chains, because they are thought to stimulate hunger.

Since colors used in popular logos and labels inevitably become intimately associated, in the mind of the buyer, with the products they represent, they must be consistent and repeatable from day to day and batch to batch.

Manufacturers have traditionally entrusted the color quality of their labels and packaging to visual inspection. However, varying color sensitivity from person to person, differing inspection environments and the ability to accurately define, communicate and document color differences may adversely influence visual inspection results. Behr Process Corporation, one of the largest paint manufacturers, has always been focused on these and all other color issues involving its products and market presentation.

In a time consuming process, various color combinations on paint labels are visually inspected. They are compared to approved color standards. Inspection results are written on inspection sheets and transposed onto a computer. Results are submitted to the supplier who attempts to make any necessary color adjustments.

This is why Behr started looking at spectrophotometers for in-house label quality standardization. They would allow Behr to adequately quantify or define color differences. Previously, it was difficult to describe how much of a change had to be made without reference to spectrophotometer data.

For a color to be repeatable, it must first be defined. Colors can generally be defined in terms of hue, value and intensity. Hue is the name of the color. Value refers to the degree of lightness and darkness assigned to the color. Intensity refers to a color's brightness. Two greens may be equally dark in value, but one may be a brilliant green and the other may be dull or flat. To accurately define a color, its hue, value and intensity must also be definable.

The desire to improve the consistency and speed of the inspection process led Behr to investigate the color guide 45/0 manufactured by BYK-Gardner. The need to objectively define colors started Behr looking at color instruments.

The color guide provides most of the features and performance of a laboratory spectrophotometer and yet weighs a little more than one pound. The guide's 45/0 geometry (45-degree, circumferential sample illumination and 0-degree viewing angle) provides the best correlation to human visual color assessment.

Objective evaluation of color is essential to the quality control process. Even though products may consist of colored parts and labels that come from different manufacturers at different times, all must match in color. The spectrophotometer allows manufacturers to generate the same color batch after batch. This is necessary because consistent color in the package implies consistent quality in the product.

One Behr customer makes bottle caps for Heinz Catsup. It wanted to ensure the color of the cap remains white. If a consumer looks at two bottles of the catsup and one cap is off color, he is going to think that bottle is old and will buy another brand. Even though it uses only one color, white, it still has to make sure that color is duplicated because each time the shelf is restocked, the caps will be from a different batch.

In the past, color analysis was performed in the lab using bench-top equipment. However, valuable time was lost in taking parts from the assembly line for color testing in the lab. In some cases, these delays were so devastating to the production process that companies would revert to visual inspection. The desire to eliminate product delays coupled with the need for repeatable color analysis fueled the development of accurate, easy-to-use portable instruments.

The color-guide provides inspectors with a portable instrument that has the same capabilities as bench-top units. Instead of having to bring products to the lab for testing, measurements can be taken on line or in the field.

Developing a new portable color instrument meant developing a reliable consistent light source. Most color measurement instruments use tungsten or xenon lamps to illuminate the specimen. Since both of these lamps can be expensive and may generate a fair amount of heat, the supplier investigated alternative light sources.

Advancements in LED (light emitting diode) technology made a breakthrough in portable color instruments possible. LEDs are long lasting, have low power requirements and require virtually no warm-up time. But some development was necessary before they could be used effectively in instrumentation.

Originally, LED's were only available in a limited number of colors, and they were not bright enough to use in color instruments. In the past five years, however, they have become available in different colors, hence they could be put in portable instruments.

At the heart of the system is a circular arrangement of 30 LEDs in 10 distinct, overlapping colors that span the entire visible light spectrum. Three LEDs of the same color are spaced on the circle 120 degrees apart. These LED triplets illuminate the specimen successively in less than three-tenths of a second. The sample is illuminated at a 45-degree angle from three locations to minimize the effects of the sample's texture. A detector collects and measures the light reflected from the specimen at zero degrees and transfers it to an internal processor that calculates and quantifies color.

The labels used by Behr Process are typically delivered in heavy packages of 500 or more. Color tests are performed on representative labels from each package before they are applied to product containers. The portable analyzer saves bringing hundreds of 20-lb packages of labels to a fixed testing machine.

Disputes regarding color values are eliminated since the spectrophotometer documents measurement results. A computer interface allows data to be directly transferred to WindowsTM applications where it can be used to create graphs and perform statistical evaluations.

The color-guide assigns a number to the relative lightness and darkness of colors on its L Scale. It can also assign numbers to scales that represent a color's red/green content and its yellow/blue content.

In addition to comparing absolute color data, Behr uses the spectrophotometer's pass/fail mode to perform rapid inspections on labels and containers by using the color data and acceptable tolerances stored in its memory.

Once color readings are stored, Behr can check large batches of labels by switching the analyzer to its pass/fail mode. The color-guide has cut Behr's inspection time nearly in half.

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