Colour match

The solution in A is now treated with mercuric chloride and methyl-red, and then titrated with Ml 10 HCl until its colour matches that of the solution in B. The difference in the volume of HCl run in from the burettes A and Bi is a measure of the amount of urea present. 

Walpole technique of colour matching 655 Wash bottles 91... 

Madsen, H.L. et al.. Cochineal as a colorant in processed pork meat colour matching and oxidative stability. Food Chem., 46, 265, 1993. 

Glass polyalkenoate cement has a unique combination of properties. It adheres to tooth material and base metals. It releases fluoride over a long period and is a cariostat. In addition it is translucent and so can be colour-matched to enamel. New clinical techniques have been devised to exploit the unique characteristics of the material. 

A restorative material can be used for the aesthetic restoration of the front (anterior) teeth only if it is as translucent as tooth enamel. This is because colour matching depends on translucency as well as hue and chroma. 

Dental silicate cement is used for the aesthetic restoration of anterior (front) teeth because it is translucent and so can be made to colour-match tooth enamel. It is prepared by introducing powder into the liquid gradually in order to dissipate heat, although the exotherm is not so great... 

Evaluation of these optical properties may be done by simple observation this approach is useful clinically (Knibbs, Plant Pearson, 1986), since acceptability of the colour match to the surrounding tooth material can be readily seen without the need for instrumental measurement. On the other hand, for quantitative evaluation of optical properties, some kind of instrumental measurement is necessary, and the property usually evaluated is opacity. 

Colour and opacity have been foimd to be connected for glass-ionomer cements (Crisp et al., 1979 Asmussen, 1983), with darker shades giving increased opacity. However, this is merely a consequence of the underlying physical relationships, and is not thought to be a clinical problem (Wilson McLean, 1988), mainly because the stained tooth material for which the darker shades are necessary for colour match is itself of reduced translucency. 

Orion Constellation This is a mosaic picture of 18 (6x3) frames. Additional four frames are added around the Barnard Loop region to increase S/N. Vignetting of the telescope is corrected by flat fielding, using proprietary software written in IDL. Distortion correction and initial colour match is done in Registar, with final colour correction and mosaic processed using Photoshop. (Reproduced by permission of Wei-Hao Wang, Institute for Astronomy at University of Hawaii)... 

This development has also been necessary because of the increased automation in many colour-using industries. For example, a computer colour match prediction recipe may call for the use of exact amounts of particular pigments and these have to be metered by volume into the machine that shapes the finished article. This simply cannot be done using dry powders, which were at one time the principal products of pigment makers. Dispersions of the component pigments with precise and constant colour strength are essential if large numbers of the finished articles are to be kept within acceptable colour tolerances. 

Mordant dyes are notoriously troublesome from the viewpoint of colour matching because the hue of the chromium complex usually differs greatly from that of the unmetallised parent dye (section 5.4.1). If other metal ions are present in the treatment bath or on the fibre during chroming, the colour obtained is likely to differ from that of the pure chromium complex. Certain important chrome dyes, including Cl Mordant Black 11 (3.29) and Black 17 (3.30), are particularly sensitive to traces of iron or copper. The hue of the black dyeings obtained is redder in the presence of copper and browner with iron contamination. The fastness to light and wet treatments may also prove inferior under these conditions. Even certain 1 2 metal-complex acid dyes show similar effects in the presence of these impurities,... 

Colour, gloss and surface texture are critical for many applications of plastics whose functions are aesthetic or where a colour match is required. 

As for metals, many painted parts have to achieve a colour match with other parts. 

Stiles, W. Burch, J. (1959) N.P.L. colour-matching investigations Final Report. Optica Acta, vol. 6, pp 1-26... 

Colour-Matching. It is essential in producing all types of laminates to ensure tight control of colour (acceptable matching, sheet-to-sheet, should be possible even between batches made several years apart). It is not possible to match papers either before or after impregnation with the precision required and hence all plain colour and printed papers are colour-matched after lamination. In addition to visual judgment it is normal to use spectrophotometers and associated computers to decide colour acceptance (or otherwise). 

Capabilities include colour matching, foil stamping, holograms, unusual die cuts, and high-resolution ink jet imaging. They can also add signature panels, bar codes, encoded magnetic stripes and individual... 

What options exist for conducting this search for a colour match Figure 2 illustrates several possible approaches, in which the crosses show the points visited during a search and the circle shows the actual colour of the chip. 

The dumbest of these search methods by some distance is one in which colours are chosen for matching completely at random. In a random search (Fig. 2a) a colour is chosen blindly from the wheel for comparison with the paint chip. If the colours match, the search is over, but if there is no match, another colour is chosen at random and the process is repeated. This kind of search has almost no merit beyond simplicity. Even in the small search space of this problem it is inefficient, while for large spaces the probability of success falls to near zero. Furthermore, the search may revisit points it has already checked, which is unproductive. (This is avoided in a TABU search, in which a tally is kept of points previously visited, but maintaining a TABU list adds computational overhead which becomes increasingly onerous as the search progresses and cannot pretend to rescue what is a very poor method.)... 

The MacAdam optical sensitivity chart shown in Fig. 26.21 does not take luminence into account and Silberstein (Phil. Mug., 1946, 37, 126) showed that when these ellipses were transferred to the three-dimensional version of the ehromatieity chart they would be ellipsoid as shown in Fig. 26.23. In order that a really satisfactory universally applieable speei-fieation for tolerances in colour matching can be established it is desirable that these ellipsoids should be spherical. This, unfortunately, is not possible and the nearest approach is the Simon and Goodwin system whieh takes the form of about 100 different charts in which, by alteration of the angle of the eo-ordinates of the ehromatieity chart the ellipses are COn-verted to eireles. The scale is such that each half-inch is equivalent to a threshold value of discrimination Fig. 26.24 (Shiot and Goodnih, Amer. Dyes Rep., 19.58, 105). 

Desbled, L. B., Exact Colour Matching and Specifying, Paris, Technological Industrial... 

Paterson, David. Colour-matching on Textiles a Manual Intended for the Use of Dyers,... 

BS (1967). Standard specification for artificial daylight for the assessment of colour. Part 1 Illuminant for colour matching and colour appraisal. British Standard 950 parti. 

NOBBS, J. H. (1997) Colour-match prediction for pigmented materials. In Colour Physics for Industry, 2nd edn, ed. R McDonald, 292-372, Society of... 

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