EPISODE 1: An introduction to flat glass processing

Sarah: Hello and welcome to the first episode of Listen LiSEC, the podcast for glass processors. I am Sarah Hummelsberger, part of the Lisec Marketing Team. Across from me sits Harald, my co-host— but maybe you'd like to introduce yourself?

Harald: Hi, I’m Harald Miksch and I work as a product manager here at LiSEC. And I will be the one who tries to answer all the questions Sarah has.

Sarah: I’m looking forward to that. We are recording today at our production plant in Lower Austria, and our studio is located inside the training centre. So outside you might hear an IG line or a cutting table – but that's getting ahead of ourselves - today, we want to focus on the very basics. And the most basic question is: What is glass?

Harald: Basically, glass is a transparent, amorphous material that is made by melting a mixture of sand, limestone, soda, and other ingredients.

Sarah: All right… so what does amorphous mean?

Harald: When a material is amorphous, it means that it lacks a crystalline structure. This property allows the material to be processed in specific ways that would be impossible with a crystalline material, for example, they can be moulded into complex shapes, blown into thin sheets, and drawn into fibres.

Sarah: You said sand is a main ingredient – like I can grab a fistful of sand off the beach and make glass?

Harald: Probably yes! Because beach sand contains a lot of quartz - different from dessert sand for example.

Sarah: And what do I do with the correct sand?

Harald: A mixture of sand, limestone, soda, and other ingredients such as pieces from recycled glass are heated together until they reach the consistency of honey. This viscous liquid is poured onto a tin bath, which does not mix with the glass and does not allow it to sink. The pouring speed determines the thickness of the glass, the width is fixed by the process.

Sarah: So they start the furnace in the morning and produce glass?

Harald: Not quite. You must visualize the dimensions of a glass works: a 500 m production line with a continuous ribbon starting at the furnace, tin bath, annealing – which means controlled cooling, quality control and at the end the cutting station. If you would shut it off, the glass in the furnace and the tin in the tin bath would become solid, and it would take ages to get it back up and running again. Therefore, such a production runs 24 hours a day for approximately 15 – 20 years.

Sarah: Impressive. What’s the end product like?

Harald: What comes out of such glassworks are so-called jumbo raw glass sheets with 6 by 3 meters dimensions – that’s almost 20 by 10 feet – and thicknesses usually ranging from 4 to 12 mm, which is 1/8th of an inch to ½ an inch. These are stacked on large racks and transported to glass processing companies with special trucks.

Sarah: So now we’ve arrived at the core topic of our podcast: glass processing. Perhaps this is the moment to define a few terms which will recur over and over. Give me a single sentence on these terms: Toughened glass

Harald: Toughened glass is a glass which is heated and cooled in a very controlled way so that it shatters into very small, blunt pieces, which makes it harder and safer at the same time.

Sarah: Coated glass

Harald: Coated glass is glass with a very thin layer of material on one or both sides which provides additional function, such as sound proofing, UV filtering or IR reflection.

Sarah: Laminated glass

Harald: Laminated glass consists of two or more layers of glass sandwiched together with foil in between, which holds the pieces together in case of breakage – like we use in windshields or even bulletproof glass – but can also add other cool functions, like UV filtering, sound filtering and even displays.

Sarah: Insulating glass

Harald: Insulating glass or IG can combine float glass or any of the aforementioned types of glass into a unit where these glass types are held together by spacers, creating air pockets in between that can be filled with insulating gas.

Sarah: I can feel you chafe under that one-sentence limit – probably all those topics deserve separate episodes! One more term that always confuses me – pieces of glass are either called sheets or panes. Are those terms interchangeable or do they have different meanings?

Harald: Many people use them interchangeably, but if we’re getting technical about it, a sheet of glass usually refers to an unprocessed float glass, while a pane usually means a cut and processed piece of float glass.

Sarah: So now we’ve discovered what the end products could look like – how are they made? Can you give us a quick walk through a glass processing plant?

Harald: Everything starts with the call from the customer and the order of, for example, a rack full of IG units. The information goes from an order management system into production planning – a very central part of the process because it considers the load and the capabilities of each machine to define the exact steps of the production process. This process begins with cutting from jumbo sheets to single glass panes, which are then, depending on the end product, toughened or laminated. In parallel, spacers may be produced.

Sarah: I wonder if working with glass is dangerous – aren’t all those glass edges sharp as knives?

Harald: Indeed, they would be – and in former times, they used to be quite sharp and dangerous. Around 10 years ago, many countries introduced regulations which require every cut piece of glass to have seamed edges.

Sarah: What does seamed mean?

Harald: It means the edges get ground to lose the sharpness. Then they are relatively safe to handle. Still, cut-resistant gloves are a good idea and commonly seen in the production.

Sarah: Circling back to the process, now all the individual pieces are ready – what now?

Harald: The assembly of an IG unit happens on an IG line. There the glass panes are washed; the spacer is applied, and the components are pressed together while gas is filled into the chambers. Finally, a sealing material is wrapped around the outer edge of the unit to ensure gas tightness and stability.

Sarah: And how is the quality of the final product assured?

Harald: There are quality checks at almost every step of the production process – the final check is done at the end of the IG line, where a scanner verifies the unit meets the agreed quality specifications. But obviously, the earlier in the process you detect a quality issue, the better.

Sarah: So that’s a lot of process steps that need to be coordinated for an in-time delivery.

Harald: Yes, and everything must be considered already at the point of cutting. And the process of cutting glass is an art form, due to the unique characteristics of glass.

Sarah: But that will have to be the topic of our next episode. Thank you for today’s insights, I am very much looking forward to hearing about this art form you mentioned.

Harald: Thanks for having me. I am looking forward to our next session.