Spectral color reproduction minimizing spectral and perceptual color differences

In this article, we are combining minimization criteria in the colorant separation process for spectral color reproduction. The colorant separation is performed by inverting a spectral printer model: the spectral Yule‐Nielsen modified Neugebauer model. The inversion of the spectral printer model is an optimization operation in which a criterion is minimized at each iteration. The approach we proposed minimizes a criterion defined by the weighted sum of a spectral difference and a perceptual color difference. The weights can be tuned with a parameter α ∞ [0, 1]. Our goal is to decrease the spectral difference between the original data and its reproduction and also to consider perceptual color difference under different illuminant conditions. In order to find the best α value, we initially compare a pure colorimetric criterion and a pure spectral criterion for the reproduction, then we combine them. We perform four colorant separations: the first separation will minimize the 1976 CIELAB color difference where four illuminants are tested, the second separation will minimize an equally weighted summation of 1976 CIELAB color difference with the four illuminants tested independently, the third colorant separation will minimize a spectral difference, and the fourth colorant separation will combine a weighted sum of a spectral difference and one of the two first colorimetric differences previously introduced. This last colorant separation can be tuned with a parameter in order to emphasize on spectral or colorimetric difference. We use a six colorants printer with artificial inks for our experiments. The prints are simulated by the spectral Yule‐Nielsen modified Neugebauer model. Two groups of data are used for our experiments. The first group describes the data printed by our printing system, which is represented by a regular grid in colorant space of the printer and the second group describes the data which is not originally produced by our printing system but mapped to the spectral printer gamut. The Esser test chart and the Macbeth Color Checker test chart have been selected for the second group. Spectral gamut mapping of this data is carried out before performing colorant separation. Our results show improvement for the colorant separations combining a sum of 1976 CIELAB color difference for a set of illuminants and for the colorant separation combining a sum of 1976 CIELAB color difference and spectral difference, especially in the case of spectral data originally produced by the printer. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 494–504, 2008     

Process conditions affect pigment quality and yield in extracts of purple sunflower hulls

Extract of purple sunflower hulls is a potential red food colorant; however, suitable process conditions must still be identified. Selected process variables were studied using bench-scale units to prepare, clarify, concentrate and spray dry extracts. Concentration by evaporation at 32°C and addition of maltodextrin to 15% (wt/dry wt) prior to drying largely eliminated pigment degradation during those steps. Relative to water extracts, extracts prepared with 5 to 15% ethanol in water generally yielded more pigment with similar levels of degradation and loss during subsequent processing. Use of 5% ethanol/2% citric acid reduced yield by about half relative to water, but gave a powder with a lower degradation index and wetting time. Percentage recovery of pigment during concentration and drying was not greatly affected by solvent type or extraction temperature.     

Note calibrating low‐scattering samples using Kubelka–Munk model

Two calculation forms are presented for calibrating a Kubelka–Munk (KM) translucent layer using white and black backgrounds. The equations, derived from the hyperbolic and exponential forms of the KM equations and replacing variables a and b with c = S/K and d = bc, give results identical to the usual method, but avoid near‐zero divisions in the low‐scattering limit. © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 399–401, 2016     

Industrial applications of formulation computations: Is the computer the enemy?

The basis of modern computations of colorant formulations is a 1931 article by Kubelka and Munk. Virtually all the subsequent important contributions to the problem were published in the following four decades; if it were the practice for software instructions to include a comprehensive list of published references, it is unlikely that many, if any, would be dated later than the advent of the modern computer. This implies either that no major problems remain unsolved, or that some factor is discouraging further improvements or is inhibiting their publication. This leads to the hypothesis that the accepted practice, in the dissemination of computer documentation, of failing to provide references to relevant published work is a significant basis of stultifying new development. It is accordingly urged that promulgators of software accept the responsibility, universally observed in scientific and technological publication, of disclosing prior work by supplying appropriate lists of relevant published material. The failure to disclose prior published work should be deemed a form of plagiarism. © 1996 John Wiley & Sons, Inc.     

栀子蓝色素性能测试及应用研究

本文报道了栀子蓝色素耐pH稳定性、耐热、光稳定性及金属离子、氧化剂、常用食品添加剂对其的影响，紫外、红外分析等性能测试及栀子蓝在食品、日化、医药等行业中的应用研究。试验结果表明：栀子蓝色素具有稳定的使用性能和广泛、良好的应用前景．     

牙膏色素原料中微生物检验方法的优化

以牙膏中色素原料作为研究对象,按照《中华人民共和国药典》(2015年版)中对需氧菌总数计数方法验证的规定,对比了色素原料微生物检验的常规法和薄膜过滤法。结果表明,采用常规法测试很容易产生假阴性的结果;薄膜过滤法对4种致病菌的回收率符合《中华人民共和国药典》(2015年版)的要求,结果准确可靠,可用于色素对需氧菌总数的检测。     

着色剂对PET树脂特性粘度的影响

依据色素分子的性质，将着色剂进行了分类，并以此为基础讨论不同着色剂对聚酯特性粘度的影响，通过Mark-Houwink公式，推导了着色剂的加入与聚酯特性粘度之间的关系，发现小分子染料会使聚酯特性粘度迅速下降，聚合染料基本不影响聚酯的特性粘度，而熔融活性着色剂在低浓度范围内对聚酯起着明显的增粘作用，不仅可提高着色牢度，还可以抵消由于热加工而引起的聚酯的热降解。     

着色剂在金矿尾渣玻璃中的呈色

采用金矿渣为主要原料，添加适量的玻璃形成剂和玻璃改良剂，促进玻璃的形成，并把它作为基础玻璃，加入着色剂，重点研究了氧化铁，氧化锰，氧化铜手工艺 着色效果，制取经济实用的金矿渣玻璃。     

仿瓷玻璃酒瓶的研究与生产

与陶瓷酒瓶相比，玻璃酒瓶有许多优点，本文介绍了六种仿瓷玻璃酒瓶的化学组成和生产要点。     

水性仿古漆——重塑木材自然气质的涂装工艺

水性仿古漆(水性擦拭型着色剂)在水性木器涂料涂装工艺中能塑造出木材自然的纹理气质,可同目前的溶剂型涂料涂装效果相媲美。