Color matching applications

It is desirable for the record to have an objective statement of the nature and degree of color deterioration. The simplest, but least desirable, method is comparison of sample color with color charts or plates such as those used in the Munsell system, Ridgeway s color standards, or the Maerz and Paul dictionary of color. Such a method is limited in value because of the difficulty of obtaining true color matches, and because of variations due to human error. The use of color charts or plates may be much improved in the Munsell system by employing a disk colorimeter (29). Kramer and Smith (21) have pointed out that the results obtained in its application to foods are sometimes difficult to explain and compare, and that the method requires special training of the operator and is tedious and cumbersome. 

With the exception of single-crystal transmission work, most solids are too opaque to permit the conventional use of ultraviolet/visible (UV/VIS) electronic spectroscopy. As a result, such work must be performed through the use of diffuse reflection techniques [8-10]. Important work has been conducted in which UV/VIS spectroscopy has been used to study the reaction pathways of various solid state reactions. Other applications have been made in the fields of color measurement and color matching, areas which can be of considerable importance when applied to the coloring agents used in formulations. 

The most important UV/VIS applications have been in the fields of color measurement and color matching, areas of great importance to the dye, paint, paper, textile, and printing industries. The pharmaceutical industry has similar interests in that the use of coloring agents in formulations requires specification. Reflectance spectroscopy has been used, however, by a number of workers to study the kinetics and mechanisms associated with a variety of reactions that were found to take place in the solid state. 

Foundry resins, phenolic, 18 788—789 Foundry sand, chromite application, 6 493-494, 497 4A zeolite. See Zeolite 4A Four-component color matching system,... 

Composite resins allow for color matching, conservative cavity preparation, and simple preparation through intraoral photopolymerization. These advantages have made composites an increasingly popular substitute for amalgam in dental restorations, especially when aesthetics are of concern. In this article, we will focus on the actual process of forming dental composites, the properties of the composites that are formed, and a complete description of the photopolymerization of the multimethacrylates that produce the dental composite. We will only be focusing on the use of polymers as dental restorations. Other dental applications of polymers, e.g. dentures and ionomer cements (reviewed elsewhere by Scranton and Klier) will not be addressed. 

Though the Kubelka-Munk theory has proven to be adequate in many applications, it has significant deficiencies that prevent it from being a total solution for color matching. Kubelka-Munk theory continues to be popular because it provides simple analytical equations and reasonable predictions [2]. 

Contemporary color-matching systems enable sample additions to the calibration database for increased performance. In addition, the sample set is variable for each individual colorant. An application may require only 5 samples for a yellow colorant but 12 samples for a reflex blue to achieve optimum performance. Note that additional samples, are used in the calculation of the absolute K and S data. These samples are not a function in a search-and-correct calculations. 

Sample Characteristics. In many Kubelka-Munk color-matching systems the user is required to present an opaque sample to the spectrophotometer. Depending on the application, this can be done a number of ways. For coatings, the technique of cross-coating several layers of colorant until opacity is achieved is commonly used. The generated sample then has become inconsistent with the typical process thickness. Although this can add error to the formulation, it will still adhere to the limitations of the Kubelka-Munk equation [7],... 

Both reflectance and transmittance measurements can be applied to the same database. For plastics and translucent liquids and for printing or coating on nonopaque substrates, this is a very important feature. In these applications it is not sufficient to match a standard in reflectance only a transmission match is equally important. Contemporary color-matching systems can combine both types of matches in one calculation using only one database. To use this capability, it is necessary that the spectrophotometer measure both the reflectance and total transmittance of the sample. 

Considering the full scope of many applications, traditional color matching has not provided a total solution for color matching. With the addition of the many-flux theory, and spectral matching, contemporary color-matching systems are the next step in providing a total solution for color formulation. 

The science of visual color matching is defined as the processes involved in achieving the match requirements, limitations, applications, performance, and processing in a final visual color match. Each step within this process must be clearly defined... 

Let us consider color match quality. The color formulator should ask the customer if the closeness of a match to the color target is the highest priority. Since there are hundreds of colorants available for the color formulator to select from, more than one possible combination of colorants may produce an acceptable match. Is the best, nonmetameric match of most importance to the customer and application If a perfect, nonmetameric match is not possible, which is often the case when trying to match plastic colorant systems to color targets in paint, ink, ceramic systems, or plastic media, will the customer accept some metamerism Also what light source will be the customer s preference when judging a slightly metameric match ... 

The reader should learn as much as possible about the properties of colorants and polymers as well as about plastics processing and plastics applications. Colorant selection is the hard part. Color matching is easy. 

Color match accuracy is just one of many requirements that have to be met in any color formulation project. If pigments are used, the quality of the pigment dispersion is critical to the formulation s cost and performance. Light stability and physical strength properties deteriorate if the pigments are not fully dispersed. Our customers are continually challenging us with new applications, some of which have no standard testing procedures associated with them. We have to work harder and... 

It is well known that a robust composite color match can be buUt from a white, a black and from two colorants (A and B) which have hue angles correspondingly smaller and larger than the required colors. The closer the hues of A and B are to the required color, the better the match will be. This is why the industrial color palettes for paints and plastics applications usually consist of 12-20 colorants, more or less evenly spaced by hue angle. As there is limited number of jets available, such a large palette is not practical for most of IJ applications. 

Fluorescent lamps are rated in catalogs by two indices, their correlated color temperature (CCT) and color-rendering index (CRI). The CCT is the temperature of a black body whose chromaticity most nearly matches that of the subject light source. Because a fluorescent lamp only approximates a "black body," it is called correlated to distinguish it from actual. The CRI on the other hand is a subjective method developed by the CIE in which eight test colors are viewed under the test and a reference lamp(s) and its ability to reproduce the test colors numerically rated. Both numbers are not absolute but useful in selecting lamps for color rendering applications. 

Careful control must be exercised during the coating process to achieve a good color match. Care also must be taken to ensure that the tablets do not become overcolored. Syrups of increasing dye concentrations usually are used to achieve a color match and to control mottling. This operation may take from 20 to 60 applications for the color to develop fully. 

The character of AR/TS is changing. Materials, equipment and applications are all increasingly sophisticated. There is more need for expert personnel, yet flexibility and breadth of outlook are required to cope with new situations. How does one predict the weatherability of plastics when twenty years service is the objective The organizers of a 1967 symposium on the subject felt obliged to conclude that after a century the problem is still far from a satisfactory solution (9). How does one predict with reliability the hazard to a large population of a new food additive or soap bacteriostat over a long period of time How does one deal with subjective properties of chemicals such as taste and flavor The synthetic sweeteners in use today have all been discovered accidentally is this the way to run a chemical business How are reluctant old timers weaned from visual color matching to computers ... 

ESTEVEZ, o. (1982) A better colorimetric standard observer for color-vision studies. The Stiles and Burch 2° color-matching functions. Color Research and Application, 1, 131-134. 

Plasticolors Inc. recently named LISA COLLETTE technical service applications representative and SARA WISCHHUSEN color match technician. Collette will provide direct technical support to customers in the polyurethane RIM, slab-stock foam and elastomer marketplace, as well as to internal technical programs. 

This paper studies multi-angle spectrophotometry as applied to integrally colored filled polyolefins for automotive applications. The paper begins by examining instrument capabilities and limitations using textured automotive parts. It also explores use of multi-angle spectrophotometiy to improve the quahty of automotive color matching in filled polypropylene systems. 

Recycled FET grades that do not require painting have been developed by AlliedSignal Flashes. The TF polyester resins (trade-named FaintFree Fetra) are produced with 100% recycled PET and mold with superior surface appearance, excellent processability, and cost-savings. Applications include automotive parts, furniture, lawn and garden tools, and power tools. Built-in consistent color matches remove the need to paint the products after molding. 

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