A forgotten product: The glass that was almost indestructable

The story of ‘Superfest’, an extremely durable, east-german drinking glass that was too durable

At the beginning of the 1970s, restaurant owners across the country complained about a shortage of drinking glasses and rumors, that the people had to drink their beer out of paper cups, had reached the government officials of the German Democratic Republic (GDR). After taking into consideration of the limited and dwindling resources of the country on the edge of the soviet union, it was decided that a more robust type of glass shall be developed that can withstand the daily use in restaurants or bars for longer periods of time.

Development started in 1975 and in 1977 the efforts in research & development culminated in the GDR patent number 157966, a glass manufacturing process that resulted in a product called “Ceverit”, which in hopes of creating a high selling export product, was also registered internationally (for example US patent nr 4397668).

“Ceverit” glass boasted a lifetime of at least 5 times that of regular glass at the time — it even survived multiple drops onto stone surfaces. In fact, the operations manager of the manufacturing plant used to demo this to visitors and potential buyers by just throwing a glass at the next wall — resulting in astonished faces as nothing happened. Because of these properties, it was dubbed “Superfest”, “super solid” in German.


To supply East Germany with CEVERIT glasses, the manufacturing task was awarded to the “VEB Sachsenglas Schwepnitz”, a glass manufacturing plant in the 2600 people village Schwepnitz.

A new building was erected and for this prestige project of the GDR an automatic and at the time state-of-the-art glass production machine from Japan was imported (no small feat at the time; remember this is a communist country at the edge of the soviet union with neither much capital nor relations to capitalist countries) to produce the base glass.

The interesting part happened after the fresh glass came out of the machine. You see, glass mostly breaks because of microscopic cracks that formed on the surface. Thus, the tighter you can get the glass surface (and increase the internal tension), the stronger and more resistant the glass becomes.

Mechanically pressing glass to increase the surface tension and reduce micro-cracks started as early as the 1800s but a chemical process to swap ions on the surface of the glass (widely called ion-stuffing if you want to know more) made it possible to harden even thinner glass like the one most drinking glasses are made of.

The developers of the process at the “VEB Wissenschaftlich-Technischer Betrieb Wirtschaftsglas Bad Muskau used alkaline aluminosilicate glass (which is also used for Gorilla-Glass found on the screens of smartphone displays today by the way) and initially submerged it into molten potash salt.

However, while the process worked just fine, it was found too slow for the envisioned production volume. Instead the glasses were passed through a stream of molten potassium salt which resulted in the same strengthening effect as a bath in potash salt.

Therefore, after the glasses came out of the japanese production machine, were passed through a stream of molten potassium salt which resulted in an ion exchange where potassium ions moved into the structure of the glass and increased the surface tension.

CERVERIT glasses survive until today and to those, who know about this type of glass, the units that go on sale on platforms like Ebay are worth a pretty penny.

The end of “Superfest”

But what happened to the manufacturing of this great product? The CEVERIT glasses took off in East-Germany and soon they could be found in almost any bar, restaurant and aboard trains. It reached a full market saturation in just a few years as planned by the government — and the product worked even better than expected: Instead of ‘just’ 5 times the regular lifespan of a drinking glass, CEVERIT in practice reached even 10 to 15 times!

By the end of the 1980s the manufacturing plant didn’t know where to store the freshly produced glasses anymore as almost everyone in the GDR had them and did not need any more because they lasted so long. More and more boxes piled up outside the production facility.

However — while this was an excellent accomplishment in the communist East and exactly what the leaders envisioned, the vendors in the “capitalist West” were less than thrilled about this invention. After all, they only made money when glass shattered in the hands of consumers, resulting in more purchases and not on more durable ones.

The lack of interest in “capitalist countries”, the market saturation in East-Germany and finally the fall of the GDR marked the end of this marvellous product — in April 1990 the production of CEVERIT or “Superfest” glasses ceased. After the union of both parts of Germany, the manufacturing plant produced regular glasses until it went bankrupt in 2004.

Sources (german)

Software Developer, avid reader, curious human

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