Colour rendering property

No. Type of lamp Rated power W Luminous flux lm Luminous efficiency lm/W Luminous density cd/cm2 Colour rendering property Additional sets... 

The very poor colour rendering property of low pressure sodium vapour lamps is due to the narrow-band emission of the Na lines (at a wavelength of 589.0 and 589.6 nm). Low pressure sodium vapour lamps are generally not within the scope of the standards for explosion protected luminaires... 

Metal halide lamps are high-pressure mercury vapour lamps in which metal halide chemical compounds have been added to the arc tube. This improves the colour-rendering properties of the lamp making it a better artificial light source for photography. 

The discovery of the working properties of clays must have resulted in one of humankind s first expressions of representational art, roughly contemporaneous with the discovery of the colouring properties of natural pigments and their use in cave art. The additional discovery that the result of the manipulation of this art form could be rendered permanent by the use of fire must indeed have been a source of wonder. The earliest fired ceramic so far known is a small moulded figurine from Dolni Vestonice in what was Czechoslovakia, dated to approximately 26000 years BP (Vandiver et al., 1989). By approximately 10000 years ago, simple utilitarian vessels were being produced in the Near and Far East. 

The mother-liquors of the lye obtained from varec contain a tolerably large quantity of a singular and curious substance. It can easily be obtained. For this purpose it is sufficient to pour sulphuric acid upon the mother-liquid and to heat the whole in a retort connected with a receiver. The new substance which, on the addition of the sulphuric acid, is at once thrown down as a black powder is converted on heating into a vapour of a superb violet colour this vapour condenses in the tube of the retort and in the receiver in the form of brilliant crystalline plates, having a lustre equal to that of crystallized lead sulphide. On washing these plates with a little distilled water the substance is obtained in a state of purity. The wonderful colour of its vapour suffices to distinguish it from all other substances known up to the present time, and it has further remarkable properties which render its discovery of the greatest interest. 

The important property of these compounds is that they will couple with aromatic amines and hydroxy derivatives to form highly coloured products which, when rendered soluble by sulphonation, give rise to a great range of dyestuffs known as the azo dyes. A simple example of a coupling reaction is shown in the following equations ... 

Many polymers in everyday use contain fillers and colouring agents that render them opaque. The optical properties of the base polymer are thus obscured. On the other hand the clarity of optical transmission of many polymers and the fact that they are almost colourless, coupled with their low density and excellent mechanical properties, are the reasons for their use to replace glass in many applications. In other applications glass would be totally inappropriate because of its greater brittleness. Other polymers, such as the ubiquitous polyethylene, are often colourless but translucent rather than transparent. 

UF resins are the most important and most used class of amino resin adhesives. " They constitute more than 80% of all thermosetting wood adhesives in Europe, and around 50% in North America. The advantage of UF adhesives are their (1) initial water solubility (this renders them eminently suitable for bulk and relatively inexpensive production), (2) hardness, (3) non-flammability, (4) good thermal properties, (5) absence of colour in cured polymers, and (6) easy adaptability to a variety of curing conditions. 

For the production of high quality porcelain, the clay must be free of all colours. The transition elements, namely Ti, V, Cr, Mn, Fe, Co, Ni and Cu, have strong pigmentation properties. When present in the lattice of the clay mineral, they impart in it a characteristic colour and may also increase its opacity due to their greater absorption of light. Furthermore, when minerals of these transition elements are mechanically admixed with the clay as impurities, even in trace amounts, they can give a coloim to the colourless clay mineral. In both ways, the transition elements render the clay useless in the manufacture of high quality porcelain. 

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