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Introduction

Glassmaking is a very old technique. Throughout it's thousands of years there has been highs and lows. In the last century, glassmaking has followed the industrial revolution of mass production. From then on, many manufacturing techniques have developed, new models have stemmed out, but even so glassmaking has still much to evolve.

Research and development of material still are, in many instances, based on empirical values, and the development of the industrial processes depend on the build up of knowledge by the engineers involved in the glassmaking process.

In order to understand the basics of the glassmaking process, right now we shall cover only the essentials, because it would be quite impossible to discuss the whole universe of glass manufacturing in a few pages.

Glass was not always manufactured by men. There are, for example, the so called natural glass, which is formed when some types of rock are fused under extremely high temperatures and quickly solidified afterwards. Such situation may occur, for instance, in volcanic eruptions, and the glass formed in this fashion are called obsidian and tektites (originating from space) what allowed humans, at the stone age, to build cutting tools for defense and domestic purposes.



Ummarized Bachground

The origins of the history of glass is full of contradictions, since the first indications that send us back to years from 7000 to 2500 BC. Historic documents are rare, and one of the first found on raw materials comes from the library of the Assyrian King Assurbanipal (668 - 626 B.C.) where it is written that in order to obtain glass it is necessary to put together 60 parts of sand, 180 parts of ashes from seaweed and 5 parts of chalk (Figure 1).

Pliny, the great roman naturalist, born on the 23rd year of our time, in his encyclopedia called Naturalis historia credits the Phoenicians for the discovery of glass.

Another quote from Pliny, the Elder, (23 - 79 B.C.) taken from book number 2 of his series "Historia naturalis" of 37 volumes talks about Egyptian merchants that transported a load of salt from Wadi Natrum near Sarepta. At the camping set up in the delta of the river Belus, which is formed by claysands from the Carmelite mountains, in order to keep the fire burning during a cold night, the men used blocks of soda to protect their bonfire, which remained lit during the whole night. On the following morning, they noticed a transparent matter that was formed and they called it glass.



História do Vidro
Figure 1


Even though this story is considered by many scholars and glass professionals a fairy tale, they claim that the fire could not have provided the high temperatures needed, we have to accept that it was well thought of, because they mention two basic raw materials (soda and sand), which are essential for glassmaking.

In the early 70's, Löber made glass out of raw materials from the river Belus and from Wadi Natrum in the ratio of 1:1 - of which the chemical analysis is shown on table 1. Surprisingly enough, the glass obtained from a fusion temperature of 1200°C resists weathering well and bears a relatively low expansion rate, as it was known from the Assyrian and Egyptian glass. Of the 25% of the calculated alkali, only 15% were left in the glass, and the excess was expelled in the form of supernatant liquid sulfate on the surface of the bath.


Tabela
Table 1



Shelby, in his book Introduction to glass science and technology, introduces a scenario where he suggests that the combination of sea salt (NaCl), and maybe bones (CaO) present in the wood pieces used to light the fire over the sand (SiO2) on the shores of the salty water sea (the Mediterranean sea?) would lower the fusion point enough, in such as way as to form low quality raw glass. Later on, the glassmaking art would have spread throughout Egypt and the Mesopotamia, expanding and consolidating itself in all continents.


Periods and regions where important innovations were developed in the ancient glassmaking art:


Major glass studies and developments in the last 300 years:

tabela

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Glass Brasil was born from a joint initiative by Sindividro - Union of Flat and Hollow Glass and Crystal Producers from the State of São Paulo and the Brazilian Trade and Investment Promotion Agency – APEX, an organ from the Ministry of Development, Industry and Foreign Trading of Brazil which main goal is to stimulate the Brazilian exports. Bringing together 9 Brazilian glass industries which masters the many ways of glass production, from the manual production to the most sophisticated automatic process (history of glass), offering a great range of products and reaching the global market.

The project enables the companies to participate of international events like fairs and exhibitions and stimulate the coming of international importers, opening new markets and allowing the members to have more notability in the international market.

This website presents part of this work and is a reference for those interested in purchasing Brazilian products. For clarity the products are ordered by firm, in their turn organised by speciality according to production processes - handmade, fusing and automatic.

José Eduardo Otero Vidigal Pontes
President of the Sindividro

Método Design