What is a Glass Vial?

Lucy Bell-Young

by Lucy Bell-Young

7th July 2021

Glass vials are commonly used as medicine or sample containers, and they vary in size, shape, and purpose. Medicine and laboratory work would be very disorganised and imprecise without the use of the small glass vial. 

Otherwise known as a phial or flaccon, a vial is typically made of plastic or glass, and usually has a resealable cap that’s either plastic or aluminium. Some caps are specially designed as composites of plastic and rubber or metal and rubber. Most plastic caps are threaded, allowing them to be tightly closed so as to maintain container closure integrity (CCI). 

How Are Glass Vials Made?

Glass vials and ampoules are mass produced either by a company that manufactures medications, vaccines, toxoids, anaesthesia, and other pharmaceutical products, or by specialised glass manufacturing companies. The latter are usually contracted by pharmaceutical and laboratory companies to manufacture specialised laboratory glass equipment and pharmaceutical vials for them. 

Numerous glass vials lying on a white table

Just like other types of glassware, a glass vial is made from silica sand, which is the source of silicon dioxide (SiO2). High quality glass is 70% silicon dioxide by weight. The silica sand, however, must be at least 98% pure for it to be useful in glass manufacturing. Additionally, it must contain between 0.025% and 0.04% of ferric oxide (Fe2O3), and the sand grains must be of precise sizes ranging from 0.075 mm to 1.18 mm.

The correct proportions of silicon dioxide and ferric oxide are important to ensure the quality of the glass vial. The requirements for laboratory glassware and glass vials are extremely technical in order to ensure structural integrity and resistance to heat.

In most cases, however, glassware products, including glass vials, use raw glass or glass blanks rather than making glass from silica sand. The mass production of glass vials is faster this way. It would require additional industrial equipment and an additional amount of time if silica had to first be processed into raw glass. 

The basic ingredients of glass are:

  1. Sand or silica: This has to be melted at 2,000°C. From here, it can be turned directly into other materials, like halogen lamps and some parts of fibre optics
  1. Sodium carbonate: This lowers the melting point of silica to around 1,000°C.
  1. Lime or calcium oxide: This counters the solubility effect of sodium carbonate in water. Other substitutes such as magnesium oxide and aluminium oxide can also be used. 
  1. Colour additives: Certain compounds can be added to molten glass to give it colour. For example, if a very small amount of cobalt is added, the glass will be blue. Meanwhile, if sulphur, carbon, and iron salts are added, the colour will be amber. You can even mimic opaque white porcelain if you add tin oxide, antimony, and arsenic.
  1. Other additives: Other substances can also be added into the molten glass mixture to alter or improve some of its properties. Some of the most common additives are:
  • Lead: Improves the reflective properties of the glass
  • Boron: A common additive in Pyrex laboratory glassware, boron changes the thermal and electrical properties of glass, allowing it to withstand extreme temperatures
  • Lanthanum oxide: Added to improve the reflectivity of glass, it’s very useful in making high quality glass lenses
  • Iron: Increases the infrared filtering ability of glass, preventing too much heat from passing through

To speed the process up even more, the basic steps in manufacturing the glass vial are now fully automated. In fact, as much as 600 glass vials per minute can be manufactured using modern machinery.

This means that, depending on production requirements and machine specifications, companies are capable of producing several thousands to hundreds of thousands of vials per day. This capability is crucial. As the global need for vaccines against the pandemic dramatically increases, the demand for glass vials is also at an all time high, with billions being needed for Covid-19 vaccines. Automation in the manufacturing of vials allows companies to keep up with this urgent demand. 

Glass vials on production line

Aside from raw glass or glass blanks, vials can also be manufactured either from moulded glass or from continuous lengths of glass tubing. Many companies also use recycled glass. Here, small vials and other types of glass containers are mass produced using either the press-and-blow method or the blow-and-blow method: 

  • Press-and-blow method: First, molten glass (known as gobs) is put into a mould. A combination of compressed air and vacuum helps the gobs take the form of the mould, pushing them onto the inner surfaces. Meanwhile, a pressing plunger is inserted below. After the molten glass has fallen into the mould and the mould has been closed off, the plunger is used for shaping. Then, in a process called annealing, the vials are reheated and cooled in a lehr to remove the stress caused by the blowing process, preventing glass breakage
  • Blow-and-blow method: The gobs are poured into a mould and the neck is formed. A parison is then made by blowing air into the molten glass so that it fills the edges of the mould. It’s then transferred to another mould for the press and blow method

Another way of manufacturing glass vials is from a continuous length of Type I glass tubing, which requires a flame and a cutting tool in order to heat up the tubing and cut off the right amount. In this process, vials also undergo annealing to reduce the stress on the glass. 

What Are Glass Vials Used For?

Glass vials are now high in demand as multi-billion units of vaccines against SARS-CoV2 (COVID-19) are being produced. These vials are resistant to extreme temperatures, capable of withstanding ranges from -180°C to 400°C. This property is necessary because, for sterilisation purposes, they have to be subjected to high heat before they’re filled with vaccines. They also need to be stored at very low temperatures to preserve the vaccines.

Glass vials are primarily used to store a wide range of medications that include vaccines, toxoids, anti-venoms, anaesthetic, and hormones. They’re very useful in storing injectables in sealed and sterile conditions. Typically, the vials for injectables are small and only for one-time use. Other types of vials are used to store biological and chemical samples for laboratory analyses.

Watch how glass ampoules are filled and sealed:

What Are the Different Types of Glass Vials?

Glass vials are classified based on their composition and intended use. Many vials are designed for pharmaceutical use, such as packaging pharmaceutical products. Others are designed to contain laboratory samples. The sizes and shapes vary depending on the purpose, but they usually all feature sealed or resealable caps.

The different types of glass vials include:

  • Type I glass containers (Borosilicate glass / Neutral glass): This type of glass container is composed of 80% silica and 10% boric oxide, with small amounts of sodium oxide and aluminium oxide. These containers have high heat resistance and are ideal for strong acids and alkalis
  • Type II glass containers (Soda-lime-silica glass/ treated soda-lime glass/ De alkalized soda lime glass): These are modified Type III glass and have lower melting points than Type I glass, making them easy to mould
  • Type III glass containers (Regular soda lime glass): These are composed of 75% silica, 15% sodium oxide, 10% calcium oxide, and trace amounts of aluminium oxide, magnesium oxide, and potassium oxide. They’re commonly used as packaging containers
  • Type IV glass containers (Type NP glass/General-purpose soda lime glass): These have low hydrolytic resistance. They’re not suited for products that need to be autoclaved. They’re commonly used for storing topical products and oral dosage products


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