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Glass enhances our environment

Louis van Wyk has spent 43 years in the glass and aluminium industry. The last 14 years were as a marketing consultant for the South African Glass and Glazing Association, which is part of the Association of Architectural Aluminium Manufacturers of South Africa. Van Wyk matriculated from Jeppe High School for Boys in the early sixties. He furthered his studies through Damelin College, where he obtained a diploma in sales management and later he enrolled with the University of the Witwatersrand for an industrial marketing management diploma. He then went on to occupy sales and marketing management positions in various companies, among others Gundle Plastics (Pty) Ltd, Shatterpruffe Safety Glass Company (Pty) Ltd, Plate Glass Holdings (Pty) Ltd, HL & H Building Supplies, Insulation World (Pty) Ltd and Henderson Sliding Door Gear.

Explain in simple terms, how is glass made?

It is a pretty long process. Float glass uses common glass-making raw materials, typically consisting of sand, soda ash (sodium carbonate), dolomite, limestone, and salt cake (sodium sulphate). Other materials may be used as colourants or refining agents to adjust the physical and chemical properties of the glass. The raw materials are mixed in a batch process, then combined with suitable cullet (waste glass) in a controlled ratio and fed into a furnace heated to approximately 1 500C. Common flat glass furnaces hold about 1 200 tonnes of glass. Once molten, the temperature of the glass is stabilised to approximately 1 200C to ensure a homogeneous specific gravity.

The molten glass is fed into a “tin bath”, a bath of molten tin (about 3-4m wide, 50m long, 6cm deep), from a delivery canal, which is controlled by a gate called a “tweel”. The glass flows onto the tin surface, forming a floating ribbon with perfectly smooth surfaces on both sides and of even thickness. As the glass flows along the tin bath, the temperature is gradually reduced from 1 100C to about 600C, and the sheet can be lifted from the tin onto rollers. The glass ribbon is pulled off the bath by rollers at a controlled speed. The flow and roller speeds vary the thickness; top rollers positioned above the molten tin control both the thickness and the width of the glass ribbon.

Once off the bath, the glass sheet passes through a lehr kiln for approximately 100m, where it is cooled gradually so that it anneals without strain and does not crack from the temperature change. On exiting the “cold end” of the kiln, the glass is into lengths cut by machines.

Who or what influenced you to pursue glassmaking as a career?

I got involved in glassmaking after I answered an advertisement by Shatterpruffe Safety Glass building products division for the position of a branch manager in Bloemfontein. They provided full training.

What subjects are required to qualify for the job?

One should have the ability to read technical drawings and building plans, be accurate with measurements and have good practical experience.

What qualities or attributes does one need to have for this kind of a job?

One must have entrepreneurial desire or ambition. Despite the lack of jobs in South Africa, this sector has enabled many young people to open their own small glazing companies.

Which sectors of the economy can one work after qualifying as a glazier?

A natural progression would be to enrol for: 

a. A glazier course run by PFG – Springs

b. The aluminium window course run by Wispeco – Alrode

c. The SAGI (South African Glass Institute) Competent Persons Course.

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Thabo Mohlala
Guest Author

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