Pigments Essay examples -- History, Prehistoric Painters

Pigments From prehistoric times, humans had discovered that pigments could be used to colour a surface and they have left their mark on their environment in the form of painted images [7]. Prehistoric painters used the pigments available in the vicinity of their homes. These pigments were the so-called earth pigments, soot from burning animal fat and charcoal from the fire. The colours available were yellow ochre, red ochre, and black [7], but with time, more colours were being discovered. In general, pigments are coloured material which is insoluble in a medium where they are incorporated [8]. Pigments will tend to absorb certain wavelength of light and reflect the others [9]. Wavelength reflected will represent the colour of the pigment. Dyes are coloured material which will dissolve in the medium and lose their crystal or particulate structure during the process [9]. Pigments can be classified into synthetic pigments and natural pigments [8]. The examples of natural pigments founded in animals and vegetables are carotenoids, chlorophyll, melanins, flavins, quinones, and anthocyanins [5, 6, 10]. In the industry, pigments are widely used as colouring agents in dyeing of cottons, silks and wool sample [11]. 2.1.1 Synthetic Pigments The first chemically synthesised pigments were made in Germany in 1704 by Diesbach who manufactured red lake pigments using potash and alkali as substrate [7]. Synthetic pigments can be divided into inorganic and organic pigments. Synthetic inorganic pigments usually composed by metal oxide or compound which from by the host of metal oxides. Moreover, the inorganic pigments possess thermal and chemical stabilities at high temperature. Most of the inorganic pigments are derived from toxic meta... ...-degradable. The increase of the packaging wastes caused serious global environmental problem [36]. Therefore, the development of biodegradable packaging materials from renewable natural resources has received widespread government support in EU countries and many national or international organisations [35]. The term ‘‘biodegradable’’ materials is used to describe those materials which can be degraded by the enzymatic action of living organisms, such as bacteria, yeasts, fungi and the ultimate end-products of the degradation process [37]. Biodegradable packaging materials may be broadly classified into biodegradable polymers and biopolymers based on whether the dominating ingredient is synthetic oil-based polymer or a biologically derived polymer. Biopolymers are naturally occurring long-chain molecules such as cellulose, polysaccharides, proteins and DNA [35].