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Color, a matter of precision

Appearance directly influences the purchase decision. Hence the importance of having an adequate system that allows color measurement, to guarantee its accuracy and uniformity.

by Vanesa Restrepo

In the paints and coatings industry, with the exception of architectural paint lines, work is rarely done for the final consumer. However, the products that formulators make are part of the final appearance of the items or projects that buyers sell to consumers.

Although the primary function of a paint or pigment is to protect surfaces, the aesthetic aspect continues to be important and influential in purchasing decisions. The reason is very simple: most consumers, after inquiring about the functional or technological conditions in a product, consider the aesthetic aspect before making their purchase decision. It is not free for other industries such as packaging and food to invest so much money in the shape, color and other aspects of presentation in their product.

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In some segments such as automotive, the offer of colors is important for the market, as many buyers prefer to have personalized vehicles, or with a classic and sober style. Both conditions are achieved through painting because color, as is well known, transmits emotions and feelings (color psychology).

For all these reasons, the precision in the color of a painting must be one of the great priorities, both for the formulator and the applicator. In the case of the first, the type of pigments used, as well as the size of these before being incorporated into the paint formula, are variables that affect the product.

Meanwhile, the conditions of application of the paint (state of the substrate, adequate pretreatment, handling of mixtures, application tools, among others) will definitely influence the final result. This without considering cases such as automotive repainting, or maintenance on durable consumer goods such as appliances, where the color and appearance of one of the parts must be exactly the same, visually speaking, as in the rest of the article.

Here then appears colorimetry, which through various instruments achieves the quantification of color, agrantizing precision. This science has had an important development for several decades with solutions for different industries such as graphics and food, among others.

To find out about the current offer of color measurement systems in the paints and coatings industry, we consulted two distributors of this type of instrument in Latin America: Exacolor in Mexico and Color Technology in Argentina.

Technological evolution

The development of color measurement instruments has been important in recent years: from having colorimeters that measured absorbance at a defined frequency of light, we move to spectrophotometers that do the calculations through the measurement of wavelengths.

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"This is the most widely used tool today. The spectrophotometer allows the human to completely eliminate the subjectivity of a visual color evaluation, explained Octaviano Fernández, manager of Exacolor, who also specified that these instruments adapt to different needs, and allow color control in the formulation and application.

"There are also teams that measure appearance, that is, in addition to color, they consider other aspects such as brightness. These are used in cases where the parts are painted independently and then assembled," he explained.

These appreciations are shared by Daniel Braguinsky, president of the company
Tecnología del Color S.A. that is present in the Mercosur countries, who assured that the main advantage of the use of a spectrophotometer is the possibility of having an objective assessment and a definition put in number, that is, an element of identity or definition of the color.

"What this does is avoid subjective interpretations that obviously vary from person to person. Obviously there are several technologies available, but the concept itself is fundamental as an essential tool to define color," he said.

Indeed, and as Fernández points out, in addition to quantifying color, spectrophotometers offer the ability to set tolerances to make the comparison against a production easier. "In addition, other important aspects can be evaluated such as: the brightness, whiteness or yellowing of a product, the strength or dyeing power, the covering power, metamerism, etc."

Precision, the key

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In order for the color measurement to give exactly the results that are expected, it is necessary to make proper procedures for sampling, measurement as such and interpretation of the results. The latter is perhaps the weakest point and can generate the biggest mistakes and therefore losses for the industry.

Braguinsky pointed out that the main human errors in the colorimetry process are, for example, "not having sufficiently clean samples, not having a well-calibrated instrument, not checking if the instrument is working according to what the manufacturer stipulates, not knowing the possibilities offered by the instrument to make optimal use of it, not see what the software that accompanies the device provides and thus go a little deeper into what the measurement is. It can also be considered not to take care of the equipment, that is, not to do the normal maintenance and care, this is an aspect that I do not know if it is so much of the people or rather of the companies, which do not make enough efforts to carry out a good training of their personnel "

The change in the measurement parameters used for the standard and the samples, is another of the most common errors within the industry, and is generated both by ignorance of the operator or person responsible, and by omission of details in the procedure.

"Measuring color is really very simple, the complex thing would be to interpret the results, so it is very important to have a local advisory service. When talking about traditional spectrophotometers, that is, equipment to measure color within the visible light spectrum, there are two ways to measure color: by reflectance (opaque colors, they do not let light pass through them) and by transmittance (translucent color that let light through them). Although the samples are located in different places of the spectrophotometer, in both cases when making a measurement it is sought to put the sample in front of the area of vision of the equipment, making sure that it fully covers the area of vision so that no light escapes. Suppose that you already have a color standard engraved, once the sample is placed the measurement is made and compared against the standard. Normally after this we proceed to save the information so that in the future we can print it or compare it with other samples and thus generate statistics, "said Fernández.

Solutions for every need

The above considerations suggest the need to have adequate equipment for color measurement. But this is a purchase that should not be made lightly, as the wrong choice can bring enormous economic and production damage to the company.

Braguinsky recommends taking into account the type of coating to be formulated or applied, to ensure that the geometry of the device is adapted to the needs of those who use it. "If one has a substrate with textures or is going to formulate non-translucent colors, it is usually convenient to use spherical geometry (dif/8º or dif/0º), on the other hand, if what is going to be measured is a smooth and even surface, the geometry 45º/0º (or 0º/45º) can be recommended and, if measurements of transparent or translucent elements are going to be made, they have to be done by transmittance."

For his part, the Mexican Fernández indicated that it is necessary to consider the sensitivity of the instrument, that is, how precise it can be, as well as the cost of its useful life: "A piece of equipment is worth not only for what is paid at the beginning, but for everything it will require to keep working properly over time", He said and added that the feasibility of having local service and advice must be studied, otherwise the maintenance costs will be high.

Our guests agreed on the importance of having an adequate light source that lasts over time. "The heart of a spectrophotometer is the light source that emits a beam that then collides with the sample and reflects a certain amount. That quantity is expressed in numbers, so the better the quality of light, the better the measurement."

In that sense, they indicated that one of the advances that has had the greatest positive impact on the industry is the use of LEDs as a source of lighting. "LEDs are super stable and durable, which allows teams using this light source to ensure very accurate measurements over time and practically never have to change it, which is a very important saving in the lifetime cost of the instrument," said Fernández.

A diverse market

In Latin America there are no manufacturers of local colorimetry equipment, as the market is small and demands a very high technological investment. However, in each country there are distributors for the main brands of equipment, who offer solutions for different industries.

When selecting your supplier, keep in mind that it is an authorized distributor, as this will guarantee technical assistance at the time of failures or require technical advice and maintenance.

When selecting your equipment, make an analysis of your real needs, considering the use you will give to the equipment, the volume of samples to be analyzed, the variety of these samples, etc. Then analyze the technical sheets offered by the manufacturers and remember that as in any other purchase decision, the cost/benefit ratio is what will tell you what the economic impact of the product is for your company.

Author: Vanesa Restrepo

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