Long-term repeatability of color-measuring instrumentation: Storing numerical standards

A major problem in the coatings industry is the preparation and maintenance of standards to be used in the shading of colored products. With the introduction of color-measuring instrumentation interfaced directly to dedicated digital computers, the storing of reflectance data as numerical color standards becomes feasible. For this technique to be practical, the color instrumentation must be stable and repeatable over a long period of time. Long-term (up to 719 days) repeatability data were obtained for seven Diano Chromascan Colorimeter-Abridged Spectrophotometers, interfaced to Digital Equipment Corporation PDP/11 computers, by measuring a set of five color-stable tiles supplied by the instrument manufacturers. Average repeatabilities of below 0.50, 0.25, 0.30, 0.30 and 0.60 FMC-2 color-difference units were found for the black, blue, green, yellow, and red tiles which make up the set. Since this is of the same order of magnitude as the uncertainties found for other systems of standards maintenance, the storing of reflectance data for use as numerical standards may be considered as a viable alternative to maintaining physical standards.     

Goniochromatic properties of human tooth dentin

This study measured the goniochromatic properties of human tooth dentin through the viewing angle dependent color change measurement, and determined the influence of the microscopic structural nonuniformity of dentin surface on the gonioappearance. Color of 21 polished dentin specimens was measured by a spectroradiometer in wet and dry conditions. Spectral reflectance values were obtained with 0, 20, 45, and 70° aspecular viewing angles to the surface. These values were converted to CIE color coordinates (CIE L*, a*, and b*) relative to the specular set (0°) standard white tile to determine general goniochromatic effect, and to the same aspecular set standard white tiles to determine the influence of nonuniformity on dentin surface caused by dentinal tubules. Color coordinates and chroma were influenced by the viewing angle (P < 0.05). As to the influence of nonuniformity, CIE L* and a* and chroma were influenced by the viewing angle while CIE b* was not (P = 0.05). Goniochromatic effect of human dentin was confirmed instrumentally, and the nonuniformity of dentin increased goniochromatic effect. Based on these results, goniochromatic properties of intact teeth should be studied further, and restorative materials that can simulate these properties should be developed. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2012     

Color Change Kinetics of American Ginseng (Panax quinquefolium) Slices During Air Impingement Drying

The color change kinetics of American ginseng (Panax quinquefolium) slices were investigated in an air impingement dryer under different drying temperatures (35, 45, 55, and 65°C) using the CIE Lab color parameters (L*, a*, b*) as the assessment indicators. Results illustrated that all three color parameters (L*, a*, b*) increased with drying time. The L* value decreased with increasing drying temperature. However, a* and b* values increased with the increase in drying temperature. Furthermore, at the initial drying stage the change rate of L* increased significantly, while towards the end of drying it reduced significantly. As regards a*, it slowly changed at the initial and final drying stages rather than in the intermediate drying stage. In the case of b*, it increased with increasing drying time and drying temperature during the whole process. The zero-order, first-order, and fractional conversion models were fitted to the experimental data, and the model's parameters were determined using linear regression analysis. By comparing the fitting of kinetic models to the experimental data, the most suitable model was selected to describe the color change kinetics. An Arrhenius equation was used to calculate the activation energy for color change kinetics and it was found that the values were 33.87–38.55, 56.48, and 74.03 kJ/mol for L*, a*, and b*, respectively. The findings of this work contribute to a better understanding of ginseng color changes kinetics during drying, and the established change kinetics models are a good tool for predicting, evaluating, and controlling of color change of American ginseng during its drying process.     

The Effect of Enzymatic Treatment on Dried Vegetable Color

The usefulness of enzymatic treatment for improving dried vegetable color was checked using carrot and pumpkin as experimental material. The color differences were expressed using the L*, a*, b* chroma and hue values. For selected samples, color attractiveness was also assessed by ranking method. The results show positive influence of enzymatic treatment on dried carrot and pumpkin color retention. The best effects of improving color of dried material were obtained for Panzym SMASH XXL (for both species) and Rohament CL (for pumpkin). The positive influence of enzymatic treatment on attractiveness of dried carrot color enlarged during storage.     

The Effect of Enzymatic Treatment on Dried Vegetable Color

The usefulness of enzymatic treatment for improving dried vegetable color was checked using carrot and pumpkin as experimental material. The color differences were expressed using the L*, a*, b* chroma and hue values. For selected samples, color attractiveness was also assessed by ranking method. The results show positive influence of enzymatic treatment on dried carrot and pumpkin color retention. The best effects of improving color of dried material were obtained for Panzym SMASH XXL (for both species) and Rohament CL (for pumpkin). The positive influence of enzymatic treatment on attractiveness of dried carrot color enlarged during storage.     

利用南方某稀土尾矿研制红地砖

以南方某稀土尾矿为主要原料,添加部分瓷土等其它条件,制备了色彩均匀的紫砂红地砖,其性能超过了国家标准GB11947－89等所规定的性能指标。     

Stability of ceramic color reflectance standards

This article reviews the long-term repeatability of spectrophotometric color measurements of ceramic color standards calibrated by Hemmendinger Color Laboratory (HCL) since it was founded 25 years ago. A set of twelve BCRA tiles was measured at HCL in 1977, and a few months later at NBS. The CIELAB color-difference, averaged over the twelve tiles, between HCL and NBS was 0.25 units. Measured at HCL about every four months since that time, the repeatability of measurement, averaged over the twelve tiles, has been better than 0.15 CIELAB units. The difference from the NBS measurements has remained at about 0.25 units over two decades. From these data the conclusion can be drawn that the tiles have not changed color during this period of time by an amount exceeding the limits of instrumental repeatability, namely about 0.15 units. © 1998 John Wiley & Sons, Inc. Col Res Appl, 23: 408–415, 1998     

高取代度阳离子淀粉改性棉纤维用于活性染料无盐染色的研究

本文以取代度为0.6的高取代度季铵型阳离子淀粉为阳离子化试剂,对棉纤维进行阳离子化改性,用于活性染料无盐染色.通过改性棉纤维表面Zeta电位变化和染料等温吸附曲线对无盐染色促染机理进行研究,对有盐染色和无盐染色中的染料色光、色牢度和染色纤维折皱回复性和强度性能进行比较,从而对高取代度季铵型阳离子淀粉的应用性能进行综合评...     

荧光增白剂对纯棉织物洗涤效果的影响

采用添加不同种类和用量荧光增白剂的标准洗衣液洗涤不同颜色纯棉织物,对比分析洗涤后织物的L*,a*,b*和C*值,反射率曲线以及目视评价结果,得到荧光增白剂对不同颜色纯棉织物的影响效果。结果表明,荧光增白剂可使增白布更白,漂白和米白布明显变亮白,浅蓝和粉红布样更加艳丽,浅灰和浅黄布样泛白或变浅,使卡其布样明显泛白,对大红、深蓝、黑色等深色纯棉织物无明显影响。     

Meat color in retail displays with fluorescent illumination

The color of beef longissimus dorsi muscle of a homogeneous group of fifteen males of Pirenaica breed in terms of the CIELAB color space was studied using the actual illuminating conditions existing in a representative fraction of retail displays operating in 51 local butcher's shops and supermarkets. All retail displays mounted fluorescent lamps and up to nine fluorescent models with different chromatic characteristics were found. Meat color was analyzed at four different times: immediately after cutting and after 1 day, 5 days, and 7 days of exposure to air. At each measurement day computed a*, b*, C* and h_ab color coordinates gave significantly higher values than the corresponding D65 values. All fluorescent models enhanced the red color of meat but none of them masked or enhanced meat color differences between samples or between measurement days. Significant differences in color coordinates were found between retail displays that mounted identical fluorescent models, proving the important role of uncontrolled environmental factors like daylight or scattered light from the walls and ceiling. With respect to computed color coordinates, the intrinsic natural variations in the color of meat samples were more important than variations in the illuminating conditions. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 304–311, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20123     

Color-pigment correlation in virgin olive oil

The chlorophyll and carotenoid content of virgin olive oils from five varieties harvested at varying degrees of ripeness were determined. Colors were evaluated from the chromatic ordinates L*, a*, b* of the absorption spectrum. Oil color changes for different varieties or stages of ripeness are directly related to pigment content and a* and b* values. The statistical study made on both series of parameters proves that there is a good correlation between them. The carotenoid content and b* have one of the best correlation coefficients (r) and is easily measured. This methodology evaluates chlorophyll and carotenoid content, an additional attribute for evaluation of virgin olive oil quality.     

Study of natural teeth color according to toothguide 3d master through cluster analysis

How natural teeth color are grouped with Toothguide 3D Master according to color coordinates, L*, C*, and h* is reported. Tooth color was measured through the Easyshade Compact (Vita‐Zahnfabrik) spectrophotometer using a sample of 1361 subjects aged between 16 and 89 years. The color of the middle third of the maxillary central incisor was registered according to the Toothguide 3D Master nomenclature and the coordinates L*, C*, and h*. Cluster analysis and the SPAD 5.5 statistical package were applied for data processing. Of the 1361 participants, only 545 (40%) had a match among the 26 physical shade tabs of the Toothguide 3D Master. Statistical analysis revealed the existence of four cluster groups: Cluster 1 comprised shade tabs 1M1–2L1.5–2M1; cluster 2 comprised 1M2–2L2.5–2M2–2M3–2R2.5–3M2–3L2.5; cluster 3 comprised 2R1.5–3L1.5–3M1–3R1.5–4L1.5–4M1; and cluster 4 comprised 3M3–3R2.5–4M2–4L2.5–4R1.5–4R2.5–4M3–5M1–5M2–5M3. Statistically significant differences (P < 0.0.1) were also found, both in the color dimension, and among the four cluster groups revealed. Taking into account the limitations of this study, the natural teeth color can be grouped into four clusters by following coordinates L*, C*, and h,* resulting from the compact spectrophotometer Vita Easyshade. Natural teeth color are not distributed homogeneously with Toothguide 3D Master according to color coordinates. © 2014 Wiley Periodicals, Inc. Col Res Appl, 41, 101–107, 2016     

Control of Color Parameters in Ceramic Tiles

Color differences found in ceramic tiles are analyzed with respect to pattern variability in time with increasing wear of the printing screen. It is found that the degree of screen wear is a critical factor in producing color shade differences. The results of an instrumental analysis of color parameters of ceramic tiles are compared with estimates of the same parameters given by consumers. A substantial discrepancy between the perception of the expert group regarding ceramic tile colors and the data of instrumental analysis is observed.     

Assessment of Color-Measuring Instruments

The U.S. Army has undertaken a program to develop an instrumental method for assessing the acceptability of textiles for color difference from a standard. This article reports the results of the first phase of the program, an assessment of three commercial color-measuring instruments (Diano Match-Scan, Hunter D-54P-5, Macbeth MS-2000) for objective textile acceptability judgment. It is concluded that the three instruments are essentially equivalent in the precision and accuracy of the measurement of color and color difference using a wide variety of samples, at least over periods of up to seven weeks. All measures of repeatability lead to the conclusion that the uncertainties involved are well below the just-perceptible color difference. Levels of absolute accuracy achieved depend greatly on the details of operation, data treatment, and calibration, but are considered satisfactory for each of the instruments tested. With respect to certain other parameters, the performance of the instruments is less satisfactory. Rejection of the specular component differs significantly among the three, as does the selection of weights for tristimuus calculations. One instrument, as tested, exhibited significant sensitivity to weave orientation in textile samples. Finally, we find that the distributions of tristimulus values obtained with each of the instruments show large deviations from normality, severely limiting the significance of conventional statistical treatment of such data.     

包裹法国红色料在陶瓷领域应用的探索

探索包裹法国红色料在建筑陶瓷工业釉料、坯体中应用的工艺技术条件，采用正交实验方法找出包裹法国红色料在陶瓷釉料、外墙砖、地砖中的最佳发色条件：在釉料中一价的钾、钠离子特别利于该色料的发色；二价离子钡较好、钙次之、镁最差；法国红色料在普通熔块中发色不理想，在特制的熔块中发色良好。     

A comparative study of color measurement lntstrumentation

A multiplant Quality Improvement Team [QIT] was firmed to develop and implement an evaluation program for various color measurement .systems as potential replacements for the then-current aging systems. The emphasis qf this article is the analytical methodology utilized to evaluate the various color systems. The evaluation program consisted cf two phases. Phase I was a general overview/review of several systems, while Phase II was an extensive internal comparative evaluation measurement systems. These were Milton-Roy's ColorMate HDS, HunterLab's Ultrascan, Datacolor's CS-5, and BYK-Gardner's The Color Sphere [TCS]. The main comparison criteria were interinstrument agreement [agreement between two instruments ofthe same system], user-friendly software and computer interface capability, vendor amenability to a long-term logistical and maintenance relationship, and price. All systems were evaluated by duplicate measurements on various color tiles, yarns, and polymer flakes-over 1600 measurements on each system. The systems were compared with an instrument matrix, a decision matrix, and a product matrix. The instrument matrix was a comparison qfinstrument parameters, software/math treatments, and economics. The decision matrix was a forced ranking of each system by each criteria category [1–4 scale, with 1 representing the best and 4 representing the worst]. The product matrix accentuated the relative importance ofone criterion category over another by multiplying the forced ranking by the criticality of the category. The criticality of a given category wus determined by consensus within the QIT. Thr combination qf the three matrices allowed the evaluator[.s] t o select the color rneasuremmt system that best satixfied the color measurement needs and requirements of their facility and their products. For this evaluation, all ofthe evaluated systems were superior to the then-current agingsystems. As a result of this methodology, one instrument emerged as clearly superior. © 1994 John Wrley & Sons, Inc.     

在陶瓷砖试验方法中用EXCEL软件处理数值修约问题

本文通过使用Microsoft Excel软件建立数值修约函数,处理陶瓷砖试验方法中的计算问题,使数据符合GB/T 8170-2008<数值修约规则与极限数值的表示和判定>,实现数据处理过程中数值修约的自动化,确保计算准确度,提高工作效率.     

Canonical biplot statistical analysis to detect the magnitude of the effects of phosphates crystallization aging on the color in siliceous conglomerates

The Canonical Biplot method is used to determine the magnitude of the effects on the Δ chromatic coordinates (ΔL*, Δa*, Δb*) and the parameter ΔE*, where (ΔL*, Δa*, Δb*) are the difference in the values of the sample after each aging cycle and the value of the untreated sample and ΔE* = [(ΔL*)² + (Δa*)² + (Δb*)²]^1/2. We performed a study of the changes in color produced by two types of artificial aging procedures on four varieties of siliceous conglomerates from Zamora (Spain) that have traditionally been used in construction and later renovations in historical buildings in the zone. To accomplish this, 25 cycles of the following types of accelerated artificial aging were carried out: (a) freezing/thawing and cooling/heating (T1) and (b) combined freezing/thawing and cooling/heating + salt (phosphates) crystallization (T2). The results of the statistical study applied (Canonical Biplot) allowed us to differentiate the magnitude effect on the color of the surface brought about by T1 as compared with T2. These effects (p < 0.05) were observed in all but one (ochre conglomerate) of the varieties, but mainly in the variable governing red hue (Δa*) and yellow hue (Δb*). © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 82–87, 2014     

Evaluation of the performance of metameric indices

Forty three metameric pairs were obtained by comparison, shade-adjustment, and redyeing of 660 self shades dyed with direct, azoic, vat, and reactive dyes. The pairs were regrouped shadewise and ranked visually in increasing order of metamerism. Spearman's rank correlation coefficients were calculated between 11 measures of metamerism and the visual metameric ranking under three illuminants A, D65, and TL84 in pairs. The illuminant-independent general indices included the indices based on reflectance differences (Bridgeman), weighted reflectance differences (Nimeroff and Yurow), Cohen-Kappauf's residual differences (proposed) obtained from the spectral decompositions of the reflectance spectra of the metameric pair. Illuminant-specific special indices included color-differences under test illuminant, addition, subtraction, division, and multiplication of color-differences under test and reference illuminants, indices based on ΔL*, Δa*, Δb* differences under two illuminants, based on chromatic adapted ΔL*, Δa*, Δb* differences with multiplicative corrections for tristimulus differences under reference illuminant (Berns-Billmeyer), differences of the color constancy indices. The present work showed that indices based on ΔL*, Δa*, Δb* differences under two illuminants, both unmodified and modified by Berns-Billmeyer performed best among the existing indices. The differences of color constancy indices showed good correlation with the degree of metamerism in some cases, and this may be utilized for developing newer indices of metamerism. © 1996 John Wiley & Sons, Inc.     

A new instrument for measuring thixotropy

An instrument was developed to measure thixotropic set of portland cements. Cement-benzene slurries were tested in two conditions: (1) under optimum thixotropic set obtained by gentle compaction of the rheopectic slurry around the rotor of the instrument, and (2) under minimum thixotropic set obtained by selected values for: (1) total load to shear the set slurry at provide values for: (1) total load to shear the slurry at optimum thixotropic set, and (2) the load to initiate flow under condition of minimum thixotropic set. The instrument appears suitable for studying thixotropic set of various finely around solids suspended with and without surface active agents in liquids perferably nonpolar and nonreactive with the solid.