Webcam to web cam for free and no credit card - Dating antique stained glass

Although color is one of the more obvious and relatively easy to describe attributes of a historic bottle, it is unfortunately of limited utility in classifying a bottle as to age or type.One of the better discussions on this is from The Parks Canada Glass Glossary by Jones & Sullivan (1989), and is quoted below:"Because colour is a universal attribute of glass and is convenient for mending and establishing minimal vessel counts, it has been latched onto by some archaeologists as a classification device.

Glass chemistry is a complex science that is beyond the goals of this website and will not be pursued here.

For one who wishes to pursue this subject, Tooley's (editor & one of the chapter authors) 1953 book "Hand Book of Glass Manufacture Volume 1 - A book of reference for the plant executive, technologist and engineer" is recommended though possibly hard to find.

Soda (sodium dioxide) - aka "alkali," "soda-ash," or "potash" in the trade (Trowbridge 1870; Toulouse 1969) - is added to the sand as a "flux" to lower the melting temperature of the silica.

Lime (calcium oxide) is added to the batch as a stabilizer since simple glass made from just sand and soda ("water glass") is water soluble making it of little use when formed into a bottle (Tooley 1953; Kendrick 1968; Jones & Sullivan 1989).

Glass composition formulas were (and probably still are) closely held glassmaker secrets as the experience of extensive trial and error experimentation in glass making was not readily shared with others.

Variations in glass color resulted from a myriad of different causes including the strata of the sand source, the mineral in the soil of the of the trees burned to produce "potash" (an "flux" alternative to soda), and many others known and unknown (Toulouse 1969a).

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.

Glass which is composed of pure silica (99.9% ) would be colorless glass.

However, making glass from pure silica is not practical or commercially viable because of the prohibitive expense of acquiring such in its pure state and the much higher temperatures needed to properly melt.

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.

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