Carbon dating archeology
05-Apr-2017 03:41
Glass chemistry is a complex science that is beyond the goals of this website and will not be pursued here.
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Having quoted this, color is still an important descriptive element for the recordation and classification of bottles.For instance, cobalt oxide added in proper quantities to a properly prepared glass batch results in a distinctly intense blue as shown in the bottle to the left.In fact, this color is known as "cobalt blue" in the glass manufacturing world (Scholes 1952).There is a very broad chronology of popularity of various colours over time; however that chronology cannot be applied to individual glass objects with any significant level of meaning..."The majority of common bottle glass is "soda-lime glass" which is primarily composed of silica, soda (aka soda-ash) or potash, and lime - the latter two ingredients often referred to as the "alkalies" (Hunter 1950; Toulouse 1969; Munsey 1970).
The silica (silica dioxide) typically makes up 60-80 % of the glass composition and is primarily derived from sand.
Although classification by colour is simple to do, the end result is of little value for the following reasons: colour does not have a direct relation with glass type (the common green, amber, and brown glass colours can occur in soda, potash, and lime glasses; many lead glasses are coloured); colour is not related to the technology of glass object production (i.e., it has nothing to do with whether the glass is free blown, mould blown, pressed, or machine made); colour is only weakly related to the function of the object (almost all colours can be found in all types of objects, an obvious exception being "black" glass which does not occur in tableware).
