| Pick a shade - any shade? by J.Park and K.Park of Park Colour Services Limited, UK, International Dyer, May 2005, page 32 Summary
Introduction
Traditonal methods of colour selection
Digital colour matching
Colour matching and 'engineered' standards production --------------------------------------------------------------------------------------------------------- Summary The history of colour development is briefly reviewed and the current state-of-the-art is discussed. 
--------------------------------------------------------------------------------------------------------- Introduction There are relatively finite ranges of fibres, yarn constructions, spinning methods and fabric-forming techniques from which to select the basis for designing a textile substrate. By contrast, the range of colours that can be applied to such substrates is almost infinite, it having been estimated that the human eye can distinguish ten million individual colours, although little evidence exists that this number of colours has been physically identified, far less produced, on a textile fabric. A wander around any clothing store will confirm that the final garments are manufactured from a relatively few, almost standard, fabric types. It can be quickly realised that the addition of colour to the substrate and the selection of the individual colours in the shade range are the major methods whereby manufacturers and retailers can differentiate their products fromaw those of their competitors. Those retailers that are seen as being successful in terms of volume of sales and profitability attribute this success to having well-designed and well-manufactured products in a range of colours that are appealing to the purchaser. The selection of fabric and garment designs is an important aspect of the product-development process carried out by the design team. Perhaps even more critical is the selection of a colour range to create a colour palette for a range of merchandise, then the creation of master 'engineered' standards for these colours, so that suppliers can create the correct colour in bulk production, to give reproducibility of colour with a given product, and on products made from different fibres and blends, especially co-ordinates.
--------------------------------------------------------------------------------------------------------- Traditional methods of colour selection Traditionally, shade ranges were created by collecting coloured samples from a number of sources in various materials. In the early days, these dubious physical samples were often sent to the matching laboratory of each potential supplier, which converted these colour ideas on to a textile substrate. Each laboratory produced its own interpretation of a match and this did not assist in achieving continuity of colour between suppliers and products. The problems associated with visual assessment together with the interpretative nature of this process and the designer's personal preferences often made this a lengthy and involved procedure. This situation was improved by the supplier sending target colours to only one independent laboratory for matching and the eventual production of standards for the approved colours.  The use of colour atlases or colour-specification products, illustrating a large number of colour patterns, preferably on a textile substrate, could greatly assist in the initial colour-selection decisions and in the matching process. Many such products were less than perfect, since they illustrated the "colours on non-textile substrates or a less-than-ideal textile material 1. Atlases based on colour-order systems are preferred, and such systems have been described 2.
Cotton, even although its world usage as a textile fibre has declined, is still the preferred substrate for textile colour atlases. A major reason for this, in addition to the pleasing appearance and drape of the fabric, is that colours dyed on cotton can be matched almost without exception on other fabric types, using the appropriate dye classes. The reverse need not be the case. The successful utilisation of such colour specifiers is proportional to the number of units that are sold worldwide. A uniformly spaced colour atlas based on the CMC colour space was developed (the PCC) 3. This was dyed on cotton with commercially available reactive dyes, to ensure adequate fastness of the product in use and so that colours could be reproduced in bulk procedures accurately and of the necessary fastness. Two further-advantages of this product are that colour can be readily created 'in space' between existing colours, and the colours illustrated on cotton are readily obtained on other substrate types with : the appropriate class of dye. A major ; high-street retailer found that, by using this colour specifier, the time taken to generate master standards, to which suppliers had to match products, was reduced from eight to two weeks.
--------------------------------------------------------------------------------------------------------- Digital colour matching Computer colour matching (CCM) technology has been well-established for several decades for recipe prediction and correction, together with the quality control of the coloured materials against a standard. In addition to the contribution that this technology makes to quick-response and right-first-time (RFT) processing, considerable financial savings are possible and these have been demonstrated 4. Physical standards become quickly soiled and the concept of using a non-physical standard (NPS), based on reflectance measurements, is not new 5. Developments in spectrophotometry, together with improved accuracy in computer colour matching and laboratory dyeing, has allowed non-physical standards in the form of reflectance data to be communicated by fax or e-mail as part of the matching process. Even when spectropho-tometers from two manufacturers were involved, the variability between instruments was found to be an average of only DE (CMC) = 0.3, when assessed by means of ceramic tiles. High levels of colour acceptance were achieved, provided that a match was obtained in the primary illuminant of DE (CMC) below 0.5 and that colour constancy was obtained in secondary illuminants. In a population of 2500 colours, matching difficulties were experienced with only three colours; one being a paper standard, a second containing a fluorescent brightening agent, and a third being a multi-fibre colour mixture. This first approach to 'colouring by numbers' allowed a significant shortening of lead times and a quicker turn around in matching. A major development in the use of non-physical standards and "colouring by numbers' has been the ability to communicate, visualise, evaluate and manipulate colour on screen. This was pioneered by UMIST, with their ShadeMaster system, was taken up by Datacolor International and subsequently commercialised as ImageMaster, and later Colorite. The features and capabilities of the system include those listed in Table 1. | Table1 - Features of ImageMaster | | Screen calibration to allow world wide communication of colour | | Input of images by scanning or from digital image data | | Availability of fully modelled images or articles, having shape, form, areas of light and shade, gloss and texture | | Colour specification by tri-coordinate systmes, colour libraries, reflectance data (from a keyboard or reflectance data from a CCM system), synthetic reflectance datat that are colour constant and realisable using real dyes | | Colours may be viewed as they will appear under any illuminant of interest | | Colour manipulation on screen to obtain desired modified colour | | Rapid and precise communication of colour and visualisation of colours and differences | The PCC colour atlas is available on a website 6 and, by loading this product into the system, Colorite will produce eight colours situated in equal spaces between any pair of original colours, increasing the size of the atlas from the original 1069 to approximately 64,000 equally spaced colours. So-called digital colour communication is becoming established as another means of achieving quick response in product development, including colour selection, together with the ability to assess both development and production products without the need to ship physical samples. Major time savings and costs benefits are achieved in colour communication for matching, standard generation, communication with suppliers and quality control in the end-product, from either the laboratory or bulk production - distance quality control. The standards can be Ioaded on to a website and password protected, giving availability to only authorised users. A further advantage of this procedure is that the 'virtual' match (illustrated on the calibrated screen) will indicate the limits of shades that can be matched, with the commercially available dyes contained in the prediction programmes of the CCM system. This can eliminate attempts to obtain colours that cannot be achieved with 'real' dyes on textile substrates. Digital colour communication and the equipment required have been reviewed 7. The necessary hardware and software are available, but real success depends on adequate training of the personnel involved and the use of standard operating procedures (SOP) by the operators and the systems manager. Web-based colour-management software involves relatively low installation and running costs 8 but, as with much technology of this kind, acceptance and market penetration has been slow 9. The development of diode-array illuminants is forecast to change colour assessments considerably, given their supposedly greater reproducibility, intensity and longer lifetimes. In addition, the use of digital image capture rather than spectrophotometry could revolutionise colour measurement. Both of these developments should lead to much more portable and accessible systems, with a reduction in equipment cost 10.
--------------------------------------------------------------------------------------------------------- Colour matching and 'engineered' standards production The textile industry has gradually evolved from mainly vertical organisation to retail-specified manufacturing, facilitated by the use of non-physical standards (NPS) and digital colour communication for colour matching, to achieve what has become known as the 'concept-to-consumer' (C2C) approach 11. However, physical standards, together with spectral (reflectance) data, are still required. This requires the matching laboratory to produce rapid, reproducible and high-quality colour matches, with small colour differences (DECMC = 0.5 or less) between target and dyeing. The generation of colour palettes and the production of 'engineered' master standards has become a mature activity, carried out by independent matching laboratories, giving an exacting service in terms of quality and speedy delivery, supported by advanced technology, including colour communication techniques, with a high level of expertise. This is a cost-effective service for the provision of standards to which suppliers must produce colours for the continued success of the retailing operation.
--------------------------------------------------------------------------------------------------------- References: - K Lewis and J Park, JSDC, 105 (1989) 152.
- A K R Choudhary, Rev. Prog. Coloration, 26 (1996) 54.
- J Park and K Park, AATCC Internat. Conf. and Exhib., (1994) 294: Colourage Annual, 42 (1995) 99; JSDC, 111 (1995) 56.
- Pratical Dyeing, J Park and J Shore, (Bradford, SDC, 2004).
- J Park and T M Thompson, JSDC, 97 (1981) 523.
- www.colourservices.co
- R L Connelly, AATCC Internat. Conf. and Exhib., (2001) 386; AATCC Review, 2 no.4 (April 2002) 17.
- J H Xin and R Lawn, Int. Dyer, 186 (Nov 2001) 28.
- R Lawn, Int. Dyer, 188 (June 2003) 27.
- T L Dawson, Rev. Prog. Coloration, 34 (2004) 72.
- J Park and K Park, Int. Dyer, 188 (June 2003) 15.
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