Colour in Recycled Crystal
Authors: Fernando Miguel Marquesa, Pedro Oliveirab
Abstract: Colour is what allows us to distinguish the world around us, through vision and light our eyes capture the colour of the objects. According to Daniel Beresniak, "colour is the effect produced by a reaction of these three variable elements: the object, the lighting and the eyes. Colour is the light reflected by a body. It depends on the incoming light (intensity and colour of the light) and the body own characteristics" (2000, p.15). The colour only exists if there is light. This paper aims to show the colour in crystal. Crystal is glass with the presence of lead that makes this glass the purest one produced by the technosphere. The common glass denominated by Sodic -lime glasses are glasses used in plan glass manufacture, container glass (bottles and jars), articles for civil construction ( bricks, blocks, tiles and shingles), articles for housing and public lighting (globes , lamps, etc. .). These don’t contain lead oxide or other more expensive materials: they are glasses that typically have green coloration (transversely more visible) due to the presence of iron oxide. Glass is by definition every mineral substance that at ordinary temperature is a nonsolid and a nonliquid. According to Navarro " even at room temperature they have the appearance of a solid body that provides mechanical rigidity , however it cannot be considered as such since it lacks of a crystal structure that characterizes it and defines the solid state . If by its stability the glass could be compared to solid, from the point of view of its structural disorder, its similarities are much more evident with liquids". Glass is more or less transparent and sometimes translucent, it has a special brightness , insoluble in almost all known substances at a normal temperature; it is amorphous (as opposed to crystalline ), it is solid-coloured or colourless, odourless; it can be smooth or it can have a texture and become one of the brightest surfaces obtained by technosphere processes. It results from the mixture of different silicates obtained by fusion in which alkali metal silicate and calcium are predominant. Crystal by its commercial demands is a glass that has a large volume of waste during its production: about 30% to 40 % of its daily production is transformed in cullet and at least 50% of this is wasteful. On average, in the only Portuguese factory that produces crystal there is a daily production of 700Kg of crystal cullet waste. As this waste contains lead, they can’t be recycled along with the ordinary glass. This is the starting point of this research project: the reuse of the crystal cullet waste, analyzing its behaviour accordingly to the colour.
Keywords: Crystal, recycling, colour.
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