Mrs Antonia Karamat* discusses how Stoelzle Oberglas’ Pharma – Health & Safety division developed an innovative, stable and environmental conscious process for the inner surface treatment of moulded Type III glass containers.

Glass is usually the first choice of packaging in the pharma industry due to its specific characteristics. It is chemically inert, can easily be heated and sterilised and therefore protects the medium stored in it from contamination.

Glass containers are categorised into Type I, Type II and Type III determined by their degree of hydrolytic resistance, which in turn depends on the degree of alkaline release.

With the world facing the COVID-19 pandemic, a new demand of Type I glass vials has been generated as vaccines are usually stored in Type I due to its highly resistant composition.

The glass market for Type I containers is expected to come under pressure to secure the supply chain and not to face shortage in the next months to come.

We believe that this will lead to pharma companies being in need of alternative, more cost-effective vials such as Type 2 containers replacing Type 1 glass for non Covid-19 products.

In line with our pharma approach and to successfully address and overcome these potentially upcoming supply chain challenges, one of our main goals has been to broaden our portfolio from Type III soda-lime glass with a moderate hydrolytic resistance to Type II glass containers from treated soda-lime glass to achieve a high hydrolytic resistance, compatible with most acidic and neutral aqueous preparations whether parenteral or non-parenteral.

In a first step, we looked into the different methods for inner surface treatment to increase the hydrolytic class of Type III soda lime glass.

Out of different approaches, the two methods used commercially today can be summarised as sulphurisation.

The process is performed either with gas (sulphur dioxide) or via a treatment with a solid (ammonium sulphate), both resulting in a reduction of the alkali ion content of the glass inner surface.

Such a treatment is generally accompanied by the formation of a washable sodium sulphate layer inside the glass.

The generated dealkalised surface layer renders the glass more resistant to interactions with products put inside the container.

However, both these techniques have substantial disadvantages: Using SO2 implies the handling of toxic gas whereas the solid process is usually less exact in dosing.

Furthermore, process stability and effectivity is difficult to achieve for small bottles in both cases.

Knowing what is important to our pharmaceutical clients, we decided to work on a different approach, which aimed to fulfil the following requirements:

  • use of a raw materials known to the pharmaceutical industry
  • allowing for a stable and safe production process with a high cosmetic quality
  • exact and uniform dosing for a large range of container sizes
  • minimising the use of chemicals to reduce environmental footprint

We are proud that following an extensive and thorough development process over the past years we are now in the position to present Stoelzle’s Type II Glass.

What is unique about Stoelzle's Type 2 glass?

Stoelzle Pharma’s – Health & Safety division has created a resource-efficient, safe and stable process incorporating the advantages of known processes without the disadvantages by using a liquid treatment process.

The main components of the liquid treatment agent for Stoelzle Type II Glass are exclusively non-harmful substances: Air, water and ammonium sulfate.

Potentially harmful SO2/SO3 is only formed in minute quantities directly in the bottles and the used water further improves the hydrolytic resistance (Fig 1).

Process of liquid inner surface treatment


The use of a liquid treatment agent and a novel process enable a reliable and exact dosing tailored to the glass size, most importantly with the use of fewer chemical materials in a process considered much safer than conventional gas treatment.

Additionally to providing our clients with the highest product quality through automated, consistent dosing via spraying, Stoelzle’s Type II also proves to have an increased hydrolytic resistance compared to inner surface treatment with gas (sulphuring).

As mentioned above, one of our declared goals was taking into account the environmental aspect in the development of Stoelzle’s new method.

Through our development of the new process, we could not only improve stability and guarantee a more even distribution for smaller bottles sizes but also:

Adhere to highest standards of work safety in production through

  • The use of harmless raw materials guaranteeing safe storage and handling.
  • Less contamination and complete removal of reaction fumes.

Minimise the environmental impact

  • Through optimal dosing of ammonium sulphate adjusted to each bottles size leading to raw material savings.
  • ‘as much as necessary - as little as possible’ – The minimum amount necessary is based on extensive laboratory tests and a substantial safety factor.

How do we ensure a continuous quality control from the start of production to packaging?

  • Process monitoring with modern sensor technology.
  • Immediate removal of all process fumes by suction and neutralisation.
  • Treatment detection with automatic rejection of poor/untreated bottles integrated into existing infrastructure.

We are now at a stage where we have performed extensive internal laboratory and inline tests and found the produced bottles in the range from 6 to 250ml significantly below the respective hydrolytic resistance limits set by US and European Pharmacopoeias for Type II Glass with little variation.

We are delighted that we already produced industrial samples of Stoelze’s Type II for selected customers, which are currently undergoing stability tests.

Stoelzle has also started with the internal and external general validation processes, which we aim to complete within the second quarter of 2020.

Our current range Type II bottles encompasses flint injection and infusion bottles from 6ml to 250ml.

Serial production of Stoelzle’s Type II is aimed to start in June 2021 in our plant in Köflach, Austria located adjacent to our headquarters.

The site is equipped with two furnaces with a daily capacity of around 270 tons of glass.

Currently, around 1.5 billion pieces of white, amber and green packaging glass are produced annually on 11 fully automated production lines.

Type III vials ready for inner surface treatment


About Stoelzle

For more than 200 years Stoelzle Glass Group has been known for its utmost know-how and excellence in the manufacturing of high-end primary packaging glass.

Stoelzle manufactures 3,1 billion moulded glass containers per year for the pharmaceutical, spirits, food, perfumery and cosmetic industry in a huge variety of different designs and sizes in its 6 production sites in Europe.

Additionally Stoelzle has 3 decoration sites and has won multiple design awards, since 2015 among others 6 times the Worldstar Award.

Stoelzle offers a one-stop-shop service for development, production, decoration and closures to its clients.

Over the past 20 years, Stoelzle Glass Group’s plants in Köflach, Austria and Hermanova Hut, Czech Republic have both specialised in the production of high-end pharmaceutical primary packaging glass.

We have gained a reputation in the field of Pharma and established ourselves as a first-choice partner to the global pharmaceutical and healthcare industry.

We currently manufacture amber, flint and green pharmaceutical primary packaging from Type III soda lime glass and were one of the first European glass factories in 2002 to produce according to the quality guidelines of GMP (good manufacturing practice) and BRC.

A strong entrepreneurial spirit is embedded in our company's culture.

We believe we can only continue to satisfy our pharma customers’ needs by innovation and continuous improvement of established production processes.

In addition to our zero-defect strategy in our processes, we rely on the latest technologies in terms of quality control and undertake continuous investments in first-class inspection machines.

Our company-wide commitment to CI (continuous improvement) also implies that we dedicate ourselves to being environmentally friendly while producing innovative and safe products to protect a patient’s health and well-being.

Our company’s commitment to environmental and social standards has also been recognised with the Ecovadis gold rating.

Stoelzle Glass Group ranks within the top 4% of all glass manufacturers according to the strict Ecovadis methodology, which is based on international sustainability standards such as the Global Reporting Initiative, United Nations Global Compact, and ISO 26000.

For further information, samples and support in the choice of the right packaging materials please contact Alexander Stern, CSCO Stoelzle Glass Group & Head of BU Pharma at pharma@stoelzle.com

*Deputy Global Sales Director BU Pharma & Sales Director Medical & Laboratory,

Stoelzle Glass Group, Koflach, Austria

www.stoelzle.com