Wednesday, 12 December 2012

Glassmaking and economics

On November 6th 2012, our class has visited a glassmaking factory at Orosháza, a Hungarian city with a strong tradition of glassmaking. The factory belongs to Guardian, one of the largest industrial glass producer companies in the world. We have seen the process of float glass-making in it's totality – from the immense heat of the glass furnace to the high-tech, automatised error scanning system. But how does this relate to the field of economics? Read below.

 The basics of glassmaking

The Guardian factory building was converted from an earlier glassmaking factory, using an obsolete technology where glass is horizontally drawn. The new technology is the so-called float technology, where melted glass is dispersed on a layer of liquid tin, creating an even surface.
The glassmaking process is made up of three main parts; the combining of materials, the melting and creation of the glass and the subsequent quality control and packaging. These activities take place in the batch house, the hot end, and the cold end, respectively.

Inside the batch house

While our group did not have the opportunity to visit the batch house, it is a nonetheless important facility in glassmaking. This is where the ratio of the materials required for glass construction are carefully measured on gigantic scales, then moved to the furnace on conveyor belts. The Guardian factory uses the following materials:
  • sand
  • sodium hydroxide
  • petroleum coke
  • glass sherds
  • limestone
  • dolomite
  • sulphates
  • Electrofiltering powder
  • Soda

Every material has a different purpuose: glass sherds help reduce the melting temperature, electrofiltering powder absorbs the harmful solid particles created while burning natural gas which is used to heat the furnace, and so on. The resulting material is a glass with homogenous chemical properties – the glasses are "specialised" in the cold end.

Getting the resources

Given the fact that glassmaking requires so many different materials, a large part of the industrial process is organised around the constant transportation of resources. Constant here means both quantity and quality - only a minority of the resources (like sand) are of Hungarian origin, while the rest are imported from around the region. For example, the natural gas used in the factory is Russian; Hungarian gas is both insufficient in volume and has a smaller heating value.

At the furnace and the hot end
After arriving from the batch house, the mixture lands in the furnace, where it quickly melts at 1100 C degrees. The melting specialists have to be extremely careful at this stage; if the mixture does not melt properly and thoroughly, the resulting glass will have serious flaws. At such temperatures, the inner chemical, physical processes are virtually untraceable; the furnace is informally referred to as the "black box". As mentioned, the heating is done by burning natural gas. The excess, oxygenated gas is constantly re-directed to the furnace space, with the direction of heating alternating every 20 minutes.

Reaching the tin bath

The melted, glowing liquid glass is then mixed by 12 stirring paddles to ensure homogenity. Then, the glass is dispersed on top of a thick tin layer, which is heated from above, and has a 8-12 cm thick liquid layer on top. Should oxygen enter the system, the hot tin would catch fire – instead, the space above the "bathtub" is filled by a mixture of nitrogen and hydrogen.
Even though this method ensures the excellent quality of the resulting glass, there are some problems. For example, the constantly vaporating tin regularly condenses on the inside of the "tub" – hence from time to time, it needs to be cleaned. Moreover, the inevitable reactions between the tin and the glass mean that the two sides of it – the atmospheric side and the tin side have different properties.

The cold end

The resulting glass can be anywhere between 4mm and 10mm – but part of the work only just begins. The continuously moving glass table goes under a quality control booth, where a computer program scans the surface of the glass for optical, mechanical, etc. faults. Differing types of glass (industrial, window pane, mirror) have differing levels of mistake tolerance; mirrors can only be created from virtually flawless float glass.
After scanning the glass, it is cut to pieces – once again automatised – and the work is seemingly done. Or is it?
In Guardian's laboratory, dozens of specialists work on developing layers for changing the colour, transparence, fragility and other physical properties of the glass. This is done by engulfing the finished glass panes in layers of purpuose-designed "molecule coats" at very high pressures, where the accompanying gases exist in a plasmic state.
Other modifications include mirror coating (this is done by painting one side of the glass panes with special red and green dyes), anti-reflective glass creation and so on.


While the Guardian factory is the only one producing float glass in Hungary, it's products supply the entire Carpathian region. Their products range from window panes in Budapest public transport buses to anti-reflective glasses used in galleries. It employs over 900 people, providing the majority of industrial jobs in Orosháza, while the Guardian is the biggest corporation of the whole county - representing how the presence of even a single factory can make or break the economic success of the region. 

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