Established in 1871, the Stoelzle Oberglas facility in Köflach, Austria is today the headquarters of the Stoelzle Glass Group and has recently been upgraded with a new furnace. Georg Feith, CEO of the Stoelzle Glass Group speaks exclusively to Glass Worldwide about strategic investment, sustainability goals and the success of the company’s Flint Prestige Recycling glass. The full version of this article appears in the July/August 2022 issue that has been mailed globally and is also now available free of charge in the digital archive*.


The history of the Stoelzle Glassworks dates back to 1805, when the first Stölzle glass factory (with the Austrian ‘ö’ still in the name) was founded in Bärnbach, in southern Austria. In 1871, a glass factory in Köflach (four miles away) was set up, initially dedicated to the production of flat glass. In the early 1880s this plant started to manufacture glass bottles, which soon became the focus of production. At that time, the Köflach team consisted of 18 glassmakers and 72 assisting workers. Raw materials such as quartz sand and lime were available nearby and the furnaces were heated with coal from regional mining.

In the 20th century the glass factory brought in semi- and fully-automated glass forming machines. The factory expanded and a decoration facility was added, offering sandblasting, frosting, screen printing and lacquering. In 1978 the two glass factories in Bärnbach and Köflach merged, becoming Stölzle Oberglas AG, which was then taken over by Dr. Cornelius Grupp in 1987, and laid the foundation of today’s Stoelzle Glass Group. Since then the Group has expanded to become a global glass network, comprising seven production sites (six European and one US plant), three decoration facilities and several sales companies.

Products offered

Today, the Stoelzle Oberglas production site in Köflach is the headquarters of the Stoelzle Glass Group and is certified according to ISO 9001:2015, ISO 15378 (GMP) and BRC GS Packaging & Packaging Materials. “Stoelzle delivers its products to customers worldwide, reaching an export quota of more than 90%,” says Georg Feith, CEO of the Stoelzle Glass Group.

The Köflach facility produces a full range of Type 3 pharmaglass (e.g. dropper bottles, syrup bottles, pill bottles, ointment jars, in amber and flint) as well as Type 2 injection and infusion vials. Besides high quality pharmaceutical products, the plant also manufactures glass packaging for food and beverages: food jars, wide and narrow neck bottles, mini spirits bottles and spice jars, as well as an extensive range of infinity jars – “glass jars that have a straight or slightly conical shape, allowing the entire contents to be dropped,” explains Mr Feith. “Our range includes infinity jars from 120ml to 545ml. These jars can be used universally and are ideal as jam jars, preserve jars, honey jars, dessert jars or yogurt jars.

Mr Feith is particularly pleased with an innovative process that Stoelzle Pharma has developed for the production of Type 2 Glass. The R&D team re-thought the treatment process by using liquid dosing for the inner surface treatment: “The so-called EcoSecur Type 2 vials are convincing in terms of safety, process stability, quality and environment,” he expounds. “This innovative technique enables reliable and precise dosing tailored to each bottle size, from the smallest 6ml vials to much bigger. With EcoSecur injection and infusion vials Stoelzle Pharma offers Type 2 glass for parenteral [injected drugs or medications] and non-parenteral applications.”

Workforce and local community

There are currently approximately 490 employees at the Köflach plant. The site has its own training centre with sections dedicated to mechatronics, electrical engineering and mechanical engineering. “Our technical apprentices and (new) employees attend specific trainings and refresher courses on real hot-end IS machines and cold-end inspection machines,” says Mr Feith. “We are proud that we have many employees, where the passion for glass has been passed on from parents to children. Parents have been with us for more than 30 years for example, and the daughters/sons have started to work at Stoelzle as apprentices…”

All Stoelzle employees have access to an enviable ‘health/well-being programme’ that includes free gym training with sports instructors, massages, shiatsu treatments – “benefits aimed to improve work-life balance, health and well-being,” underlines Mr Feith.

The Western Styria region [a state in the southeast of Austria] has been characterised economically by coal and glass for a very long time,” observes Mr Feith. “The coal mines were closed many years ago, but the glass industry is still one of the largest employers. Many people from the region have one or more family members who have worked in glass industry and the Stoelzle team comprises many families/generations, too."

Stoelzle does a lot of sponsoring, mainly focused on environmental issues, culture, sports and charity initiatives,” he continues. “We are the main sponsor of the local handball and soccer youth teams, and support also other sports associations. We have close co-operation with schools and universities, offering work during the summer holidays, for example, but also mentoring master theses for technical students. Last year we started a co-operation with a local beekeeper, financing three bee populations and obtaining hopefully a lot of Stoelzle honey, which we will pass on to employees and customers. This initiative is a contribution to protect and promote biodiversity and the pollination via bees in our region.”

Recent investment

To make the Köflach production site more efficient and more sustainable in terms of energy efficiency and CO2 emissions, last year Stoelzle Glass Group invested €22 million in the rebuild and expansion of its flint glass furnace. The project was completed in early 2022 and the facility now reaches a daily capacity of around 270tpd. Featuring advanced melting technology from HORN, the new furnace reduces the amount of energy used in the melting process by an estimated 13% per ton of glass, while improved E-boosting allows more green electricity to be used, reducing consumption of natural gas.

To ensure that Stoelzle Oberglas products are of the highest quality the Group also invested in a 12-section triple-gob tandem IS machine from Emhart, 10 Bottero IS section renewals on two lines, a new feeder, various cold end inspection machines and an All Glass dual packaging robotic palletiser. Suppliers of equipment and technology were chosen for their “eco-friendly approach and reliability in quality and delivery,” notes Mr Feith.

The Köflach plant’s manufacturing capabilities now extends to 11 production lines, two furnaces (flint and amber), with the flexibility to switch one from amber to flint as demand requires.

Demolition of the furnace started on 12 October 2021 by emptying the furnace,” Mr Feith reports. “First glass was produced again on 12 December 2021; with all lines in operation mid January. We were very lucky to complete the whole furnace rebuild in the scheduled time as we suffered from reduced personnel capacity due to the pandemic,” he confides. “Our team did a great job, being very flexible.”

Fortunately, being part of a larger Group with manufacturing plants in other countries affords Stoelzle Oberglas the advantage of having “back-up plants” during significant construction programmes. “In the case of furnace renewals or other issues, the production and supply of our products will be guaranteed,” confirms Mr Feith. Pre-planning ahead of scheduled furnace rebuilds ensures that stock levels never fall. “We take care to manufacture in advance larger stock of the items needed by our customers in order to compensate for times of low production,” he explains.


Stoelzle Oberglas’ new batch formulas based on the use of PCR glass and secondary raw materials have been examined and tested at the company’s in-house glass lab. The results show that Stoelzle’s ‘Flint Prestige Recycling glass’ will reduce CO2 emissions at the Köflach plant by 16%, along with a 4% decrease in energy consumption, without compromising on glass quality or colour.

We are working on new batch formulas which will make our glass even more sustainable,” explains Mr Feith. “Our research focuses on substitution of primary raw materials by CO2-free secondary raw materials such as industrial soda, slag sand or ash from biomass. The new formulas are tested in our in-house glass lab. Our main target is to create CO2- and energy-saving formulas, whilst maintaining our high glass quality. Taking advantage of our dedicated R&D team and the in-house glass lab allows fast progress and reliable results.”

Areas of development include process and energy optimisation; green electricity and alternative fuels; and use of PCR cullet and CO2-free and alternative raw materials. Stoelzle pioneers eco-friendly decoration with 100% heavy metal-free colours, the use of recycled ink (screenprinting ink made from old tyres), and its Quali Glass Coat technique, which saves 77% CO2 compared to liquid painting. Process and energy data management software has been implemented and energy is conserved by employing a batch preheater, recovering heat from furnace waste gas and installing photovoltaic [solar power] panels on the roofs of its buildings. In addition, the Group is conducting research on green fuels such as hydrogen, biogas, and syngas from waste gasification.

Stoelzle’s main target is to reduce CO2 emissions by 50% by 2030 and to reach climate neutrality by 2050. Focus on this objective and reducing energy consumption has been set at a Group level, with an emphasis on developing and re-thinking processes and techniques not only in production but also in the decoration of high quality packaging glass. “We have a defined CSR strategy to reach this goal,” including “being transparent in our communication,” says Mr Feith. Accordingly the Group is active on CSR platforms and “working closely with FEVE on the Close the Glass Loop project” to increase the quantity and quality of recycled glass available to the industry. In recognition of its commitments to sustainability Stoelzle achieved EcoVadis Gold Status in 2022 – “the second year in a row,” notes a proud Mr Feith: “These internationally renowned awards reflect our efforts in the field of CSR and prove that measures and initiatives are working to constantly improve our CSR credentials.”

With the promising new batch formulas at Stoelzle Oberglas and a furnace renewal planned for Stoelzle Czestochowa in Poland in mid 2022, things are already looking promising for a hat-trick next year.

Image: Georg Feith and the Stoelzle Oberglas production facility in Köflach, Austria.

Further Information: 

Stoelzle Glass Group, Köflach, Austria
tel: +43 3144 706
email: office@stoelzle.com
web: www.stoelzle.com

* The full version of this article appears in the July/August issue that has been mailed globally. The digital version of this issue can also currently be read free of charge in its entirety alongside back copies in the Digital Archive (sponsored by FIC) at https://www.glassworldwide.co.uk/Digital-Issues. To receive the paper copy, all future issues and a free copy of the new Who’s Who / Annual Review 2022-23 yearbook, subscribe now at https://www.glassworldwide.co.uk/subscription-choice

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