Colour Measurement and Colour Tolerance in the Plastics Industry

The limited use, within the plastics industry, of colour-difference units is discussed. The requirements and calibration of measuring instruments, with particular reference to plastics, are stated, together with details of reference and calibration standards. Identification and estimation of colorants is carried out with the Comic analogue computer handling a modified Kubelka—Munk function of the spectrophotometric reflectance curve. Although the scatter component of this function varies with the opacity of the moulding, the variation can be predicted and its effect nullified. The correction of a first prediction for a new colour is done through the computer by means of the differences in tristimulus values, as measured by means of a colorimeter, between the predicted recipe and the required colour. An extension of this method for colour control in production is explained. The colour tolerances achieved by instrumental control in the production of thermosetting plastics are stated in terms of the deviation (in MacAdam units) from standard. The colour gamut over which measurement may usefully be applied is prescribed. Finally, some problems associated with measurement are described, together with their solutions.     

抓好计量工作为企业生产服务

计量是以保证单位统一、量值准确一致的测量。对计量器具要实行科学管理，遵循计量工作的客观规律，为玻璃企业的稳产、高产奠定良好的基础。     

Performance monitoring of colour measuring instruments†

This technical report defines practical methods to be used for monitoring the performance of instruments used in the measurement of surface and/or transmitted colour. The report defines procedures to be used to monitor the performance of an instrument in terms of its repeatability (short term) and reproducibility (long term). The report covers performance monitoring of the following types of instrument when used for the measurement of surface or transmitted colour: tristimulus colorimeters; solid‐state array spectrophotometers; and scanning spectrophotometers. This report does not define procedures for estimating the uncertainty of measurement and excludes performance monitoring of instruments that produce an absorbance or transmittance measurement with restricted spectral range of less than 400–700 nm.     

New Instruments and Techniques for the Assessment of Variations in the Colour of Textiles

Investigation of the extent and probable causes of variability in the colour of batches of dyed and finished fabrics by means of laboratory colorimeters has revealed the need for new instruments that can (a) detect non-uniformity within and between pieces, (b) give a representative numerical specification of the colour of a piece and (c) sort pieces into matching sub-groups. Existing colour-measuring instruments are too tedious to use, and provide information that has to undergo too much processing to yield data of practical value at a speed appropriate to commercial operating conditions. Progress towards a greater degree of instrumental control of colour uniformity cannot be made until there are instruments to detect unlevelness in full-width fabric and to sort patterns rapidly into matching groups. The Shirley Colour Monitor, which records continuously colour variations along and across fabric pieces, and the Harrison–Shirley Digital Colorimeter, which is a general-purpose colour-measuring instrument with many new features, are described. Some results are presented to illustrate the performance of the new equipment in relation to practical textile problems.     

The minimum number of measurements for colour,sparkle, and graininess characterisation in gonio‐apparent panels

Materials with new visual appearances have emerged over the last few years. In the automotive industry in particular there is a growing interest in materials with new effect finishes, such as metallic, pearlescent, sparkle, and graininess effects. Typically, for solid colours the mean of three measurements with repetitions is sufficient to obtain a representative measurement for colour characterisation. However, gonio‐apparent panels have non‐homogeneous colours, and there are no studies that recommend the minimum number of repetitions for colour, sparkle, and graininess characterisation of this type of panel. We assume that colour panels incorporating special‐effect pigments in their colour recipes will require a higher minimum number of measurements than solid colour panels. Therefore, the purpose of this study is to verify this assumption by using a multiangle BYK‐mac spectrophotometer, given that it is currently the only commercial device that can measure colour, sparkle, and graininess values simultaneously. In addition, a possible methodology is given for establishing the minimum number of measurements when characterising gonio‐apparent materials using a specific instrument, able to be implemented in future instruments when determining multiple appearance attributes (colour, gloss, sparkle, etc.) for many coloration technologies. Thus, we studied the minimum number of measurements needed to characterise the colour, sparkle, and graininess of three types of sample with solid, metallic, and pearlescent coatings respectively. Twenty measurements were made at twenty random positions (different target areas) of 90 samples. The minimum number of measurements for all these variables was determined on the basis of the point at which the cumulative mean value became constant. Thus, applying new statistical tools, it is clearly shown that metallic and pearlescent panels require more colour measurements than solid panels, in particular when geometries are being measured in a specular direction. As regards texture (sparkle and graininess), more measurements are needed for graininess than for sparkle, and more for metallic panels than for pearlescent panels.     

Colour appearance in immersive three‐dimensional virtual environments

Technology is constantly evolving and, consequently, all the technological advances taking place are regularly integrated into the daily life of society. During recent years, there has been a trend towards virtual resources such as teleworking, telemedicine and e‐commerce. In many countries, this virtualisation process has been accelerated by the changing circumstances caused by the COVID‐19 pandemic. In any case, there is a growing demand for virtual systems, and virtual reality is a suitable field for the application of a multitude of solutions. However, advances in virtual reality occur without any regard to colour science, and there are several challenges to be overcome to improve the visual appearance and fidelity of colour reproduction in all types of related devices. This paper discusses three open issues related to the visual appearance and visual fidelity of virtual reality systems. We believe it is necessary to direct future research efforts in each of these directions to secure improvements in the visual fidelity of virtual reality systems.     

A multispectral imaging approach to colour measurement and colour matching of single yarns without winding

This paper investigates a multispectral imaging approach to colour measurement and colour matching of single yarns. The small size of a single yarn makes it impossible for spectrophotometers directly to acquire its spectral reflectance. Multispectral imaging systems, on the other hand, have the potential to measure the reflectance of single yarns as they can record both the spectral and the spatial information of a sample. A multispectral imaging system, namely imaging colour measurement, has been developed to conduct colour measurement of single yarns. A single yarn is first detected from backgrounds by a modified K‐means clustering method. The reflectance of the single yarn is then specified by an averaging method. Comparative experiments based on 100 pairs of single yarns and corresponding yarn windings show that the reflectance magnitude of a single yarn acquired by imaging colour measurement is smaller than that of corresponding yarn winding measured by a Datacolor 650 spectrophotometer. Experiments on 16 single yarns show that the repeatability and spatial reproducibility of the imaging colour measurement system in measuring a single yarn colour are 0.1185 and 0.2827 CMC(2:1) units. A colour matching comparison experiment (pass or fail), using 24 pairs of single yarns and corresponding pairs of solid‐colour yarn dyed fabrics, shows that single yarns measured by imaging colour measurement can achieve similar colour matching results to solid‐colour yarn dyed fabrics measured by the Datacolor 650 spectrophotometer, with degrees of similarity of 87.5 and 83.3% when the CMC(2:1) and CIE2000(2:1:1) colour difference formulas are employed.     

Virtual colour: Communication standard and analytical tool

A number of problems have been identified with existing colour specification systems and their physical exemplifications: colorimetric conditions (illuminant, observer, spectrophotometer geometry, specular component inclusion/exclusion, etc.), restrictions of the notational system adopted, and limitations of the colour atlases themselves (sample size, sample error, sample range, etc.). Developments in computer science, and in particularly CRT displays and colour printing devices, now provide increasingly more affordable alternatives to traditional colour ranges and atlases. Techniques have been developed to increase the accuracy of printed colours relative to their CRT originals, and devices are manufactured to calibrate colour monitors. However, colour selection software developed to date is still primarily based on existing colour ranges and colour specification systems, or on a more general mechanism specific to an individual application. It is argued that basing such software on an existing model of colour specification inherits some of the problems of that system: notational methodology, means of representation, and atlas limitations. It is proposed that the restrictions imposed by such software be relaxed by providing a flexible method of constructing application-specific colour specification systems with conversion to a standardized notation for accurate colour communication. Furthermore, it is proposed that such a tool would be invaluable for the evaluation of human colour perception. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 204–211, May 1997.     

Die On-Line-Messung von Partikelgrößenverteilungen in Gasen und Flüssigkeiten

On-line measurement of particle size distribution in gases and liquids . The importance of rapid response and on-line analyses of particle size distributions is becoming increasingly important in industry for the continuous supervision of product quality and the control of production processes. Instrument manufacturers already offer a considerable number of rapid response devices which can be used for systems with extremely low solids concentrations as well as for the analysis of bulk material and highly concentrated suspensions and aerodispersions. Some of these instruments are already superior to older methods of analysis. They not only save time and labour but have also opened a new dimension in direct supervision and control of production processes. This paper surveys the most important on-line measuring techniques and instruments.     

硝区特殊介质工况下测量仪表的选型应用

测量仪表在特殊介质工况下的选型应用是一大业内难题，也是硝区生产多年以来困惑仪表人员的一个棘手问题。本文对几例我公司实际遇到的测量仪表选型应用案例进行了分析和总结，对同行业有一定参考价值。     

VISCOSITY OF RECENT CONTAINER GLASS*

A high-temperature, concentric cylinder viscometer has been constructed and calibrated. The calibration checks within 1% that obtained by Lillie for a similar apparatus and provides further evidence of the high degree of reliability of this type of measurement. The contention of Washburn and Shelton that the calibration in such instruments is a function of the viscosity is shown to be false. Because four independent investigations have been unable to check this contention, it may now be regarded as spurious. A medium temperature-range fiber viscometer for measuring the viscosity of glass in the annealing range has also been constructed. It is shown that the Fulcher equation, log η=−A+B/T−T₀, fits the data obtained on the two instruments to within 0.5% for commercial soda-lime glasses. Complete viscosity data as a function of temperature are given for sixteen commercial container glasses, and the analyses are also included. These glasses show a wide range of viscosity.     

基于超声衰减和声速动态监测石蜡的相变过程

为研究石蜡在相变过程中内部结构和状态的改变特性,用中心频率为5 MHz的脉冲式超声波动态测量石蜡的相变过程,采集并分析不同升降温速率下的声速和声衰减信号的变化规律,结果与差示扫描量热仪(DSC)测量的热力学性质比较,并拍摄石蜡溶解过程的图像为辅助,探讨了二者由于测量原理不同导致的差异和特点。结果表明,两种方法均得到约50℃的初凝点,且二者信号反映的相变规律一致,表明利用声衰减和声速能够较好的表征石蜡在相变过程中的声学特性。超声可能成为一种新的蜡化物性质原位测量手段。     

Assessment of whiteness and tint of fluorescent substrates with good interinstrument correlation

White is primarily a sensation like blue, green, or red and, as such, is not measurable directly. Only a physical property, the spectral reflectance of a sample, can be measured directly. But this is not a standard, fixed quantity; it depends on a number of individual properties of the measuring instrument used. the entire geometry of the illuminating chamber—generally speaking a sphere is used for samples with a structured surface—is incorporated in the measuring results. the size of the aperture and the exclusion or inclusion of gloss also influence reflectance. High whiteness is obtainable only with the aid of fluorescent whitening agents [FWAs], and is hence a fluorescent color, which demands specific qualities of the illumination. the sample illumination must be identical with that for which the colorimetric values have been calculated. Nowadays, however, this is usually standard illuminant D65, which can be simulated only approximately in measuring instruments. In addition, all lamps used are subject to changes in spectral energy distribution. the problem is how to obtain constant, comparable results, namely whiteness, tint, and lightness for fluorescent materials using measuring instruments of different designs incorporating different means of simulating standard illuminant D65 or other D illuminants. This article presents a method that has been in use in industry for about 20 years. the method in question comprises two parts: first, on the hardware side, sample illumination that has to meet specific requirements, match the UV excitation required, and remain stable; second, on the software side, the two critical dimensions of whiteness and tint are calculated indirectly from the measuring results. Only in this way is it possible to achieve a large measure of comparability between different instruments. In principle, the method is also suitable for different illuminants and for any white preference. In all other methods of assessment the parameters are not matched to the instrument characteristics. If the results obtained with different measuring instruments are to be compared, difference values have to be used, entailing the need for standards and involving all the drawbacks associated with them.     

在线中子水分仪在玻璃自动配料系统中的应用

准确及时地测量各种物料的含水率是先进浮法玻璃生产的重要工艺控制过程,中子法测水的理论可用于在线测量物料的水分已是玻璃行业不争的事实.本文通过大量生产实践数据进行统计、归纳,深入分析了影响测量效果的相关因素,提出了一些行之有效的应用措施.     

The Use of Colour–difference Formulae in the Leather Industry

There has been an interest in colour measurement and the measurement of colour differences for a considerable number of years in the leather industry. A brief outline of their use and of the related problems is given and the application of colour–difference equations to matching, sorting and specifications is reviewed. Particular attention is drawn to the fact that no single colour–difference formula is likely to be acceptable for all productions of leather.     

Colour in newspapers

A major turnabout in industrial relations during the 1980s has led to the UK national newspaper industry becoming more viable and confident. This has led to the introduction of new equipment and processes, which in turn introduce the possibility of regular full colour newpapers. This article introduces briefly the processes that have now become outmoded, and those that have taken or are taking over from them, with more explanation of why the ‘colour explosion’ in newpapers should be under way now. It concludes with a personal view of how the UK and European newspaper industry will change over the next decade or so.     

Factors Affecting Instrumental Measurement and Visual Assessment of Colour Differences

The factors affecting the instrumental measurement of colour differences are reviewed. For most types of sample the performance of modern instruments is more than adequate provided that sufficient care is taken. Problems may arise with metameric pairs and fluorescent samples. The main source of error lies in the colour–difference equations/ this is quite separate from errors due to the instrument. Problems associated with visual assessments are discussed. The use of a panel of three observers will produce more reliable results and may be preferable under certain circumstances.     

热能表示值误差检定的测量不确定度评定

热能表属于强制检定的计量器具,其准确与否直接关系到千家万户和供热商的切身利益。国家加强了对热能表等计量器具使用环节的计量监督管理,强化了对热能表安装使用前首次检定的监督管理,加快了热能表等供热计量器具体系建设步伐,各级计量技术机构都在积极筹建热能表检定装置的计量标准,为供热计量监督提供了技术保障。介绍了测量方法及原理、不确定度的评定,提出了在热能表检定过程中,要有流量、温度和计算器的检定,还要有热量的总量检定;在示值不确定度评定中,各部分要分别评定。     

瓶级PET切片色值测试的不确定度评定

对用色度计测试瓶级PET切片色值的不确定度进行了评定,结果表明,定期对标准色板进行检定,严格样品测试的操作细节,确保样品颗粒度均匀,可以达到减少不确定度的目的。