The pie chart in Figure 2 provides a rough overview of the shares of these categories by amounts of worldwide production. The figures given are estimates based on an evaluation of multiple sources for the time span 2003–2008. By absolute amounts, the 2005 world production reached about 124 million metric tons (31 in the European Union, 8 in Germany). Since then, an average annual increase of about 3.5% is observed. Whereas the production is more or less leveling off in most industrialized countries, the PR of China is among the main driving markets for this increase as its 2005 output of flat glass already accounted for more than 50% of the world production (cf. Chapter 9.6).
For each type of glass products listed above, a typical chemical composition range has been adopted worldwide. The compositions of container and flat glass have never been developed by a scientific approach. Rather, they have remained pretty the same ever since the beginnings of glass makings (Chapter 10.2). Compositions have thus been very early constrained by the availability of affordable raw materials, the need to prevent water corrosion, and the highest temperatures reached in furnaces.
A systematic scientific approach to glass compositions did not begin before the nineteenth century, chiefly promoted by the work of individuals such as Fraunhofer, Faraday, Harcourt, Abbé, or Schott (Chapter 10.11). Since then, this scientific approach has remained the basis for designing not only the compositions of most specialty glasses but also to improve those of existing products. For example, there is a quest among the producers of continuous fibers for completely new compositions with outstanding mechanical or chemical properties such as high modulus for lightweight construction composites or extreme alkali resistance for concrete reinforcement. In other cases, the driving force for development stems from environmental or health concerns and legislation. As examples, lead and arsenic oxides are being replaced in the formulae of optical glasses, solder and sealant glasses, and even in crystal tableware, whereas insulation‐fiber compositions have been reformulated to avoid any confusion with asbestos fibers whose cancerogenic potency is well known. The typical composition ranges of current glass products are summarized in Table 1.
Figure 2 Glass production by branches; figures in % in the sequence world/United States/Europe.
Table 1 Typical compositions of industrial glasses comprising main oxides only (no colorants or impurities); compositional ranges from multiple sources (e.g. [13]) or typical individual examples (wt %).
| Oxide | Container glass | Float glass | Crystal glass | Display glass | E fiber glass | Glass wool | Stonewool | Low‐α glass | Soluble glass |
|---|---|---|---|---|---|---|---|---|---|
| SiO2 | 66–75 | 70–74 | 66.0 | 65.0 | 52–60 | 56–66 | 35–48 | 70–81 | 66–77 |
| TiO2 | 1.0 | 0–3 | |||||||
| Al2O3 | 1–3 | 0.5–1.5 | 2.0 | 18.0 | 12–16 | 0–6 | 12–28 | 2.5–5 | |
| Fe2O3 | 3–12 | ||||||||
| B2O3 | 1.0 | 0–9 | 3–9 | 10–15 | |||||
| MgO | 0–4 | 0–4 | 4.0 | 7.0 | 0.5–4.5 | 1–5 | 2–11 | 1.0 | |