Early glasses

Most ancient manufactured glasses have been discovered in tombs in Egypt (3500 BC). Also, Phoenician merchants are believed to have discovered glass in the region of Syria around 5000 BC. Their glass discovery is so far rather speculative.

In AD 77, Pliny the Elder mentioned for the first time glass technology and how it was discovered by chance. Natron blocks were used for resting cooking-pots.

With the intense heat, the blocks would have eventually melted and mixed with the sand of the beach to form an opaque liquid which would have formed a glass on cooling down slowly after the fire was stopped.

Once glass fabrication was discovered, the first glassmakers were motivated to produce decorative objects, like vessels and maybe to simulate gems and semi-precious stones using silica with appropriate colorants such as copper, manganese, and iron salt. Notably, the decorative application for glass is still attractive. Baccarat jewellery and decorative objects represent 24% of its business, with black crystals being a great attraction and success today.

The most ancient glass workshop was discovered in Egypt at Magatta palace and would have been in use by 1500 BC. The first so-called glass factory dates back to1250 BC as revealed from the survey of Qantir Pi-Ramses site in the Nile delta region by Rehren in 2006. Parallel developments of ceramic and metallurgical processes allowed for glass to be used to produce foils and glazes. The Romans formed glass foils by pouring the glass melt on a metallic plate which was covered by sand to prevent glass adhesion to the plate. The thinning of the foil was obtained by stretching it before the glass transition was passed. The glass transparency might have been then important since glass foils could have been used for windows. After the fall of the Roman Empire, the technology was dispersed with new centers being developed in the Middle East by the Arabs.

Glasses were formed over ceramics, allowing the protection of the ceramics from liquids (water, wine) and decorating the ceramic bulk. The first glassmaking manual dates to around 650 BC. Instructions on how to make glass are contained in tablets from an Assyrian library.

Blowing was invented in Syria. An iron blow pipe some1.5m long was used, one extremity being fared to sustain the glass gob. This end was warmed in the furnace before the operations so that glass would adhere better to the blowpipe. The glassmaker then slowly twisted the blow pipe into the glass melt to collect the gob (or gather). By AD 200, blowing allowed the formation long bottles which were separated from to pond bottom to form long cylinders. Such cylinders were then cut.

In the Middle Age much glass was still dark green or dark brown as a result of the impurities that were present in the raw materials. Although still little was known about glass technology at that time, it appears that more attention a paid to raw materials selection. The raw material selection procedure resulted in the rejection of alkaline earths and alumina yielding glass with poor resistance to moisture.

This resulted in deteriorating glass articles. Intentionally added CaO might date back to the 16th century, when Bohemia crystal was invented. In fact, glass manufacture was mostly developed empirically.

(a) Blowing, (b) cutting and (c) flattening.

Дата добавления: 2015-01-03