Glass Containers and Container Glass

Soda-lime glass—the standard material for most container glass—consists mainly of quartz sand (SiO₂), soda (Na₂O), and lime (CaO). This composition makes it economical, easy to shape, and versatile—for example, for beverage bottles, canning jars, yogurt jars, or household storage containers.

It is tasteless, food-safe, and offers high transparency. However, it has limited resistance to thermal shock and is less chemically resistant than specialty glasses—an important factor for sterile goods or aggressive contents.

Manufacturing process of soda-lime glass for glass containers:

Soda-lime glass can be efficiently melted and formed at relatively low temperatures (approx. 1,400°C)—ideal for mass production. The melt is continuously degassed and homogenized before being divided into gobs and blown or pressed in forming machines.
To minimize stress, cooling takes place in precisely controlled annealing lehrs. Depending on the application, the glass can be additionally coated or colored.

Soda-lime glass is the robust, reliable all-rounder among container glasses—ideal for standardized products with moderate chemical and thermal stress.

Borosilicate glass is a particularly chemically resistant glass that remains dimensionally stable even at high temperatures and sudden temperature changes. It consists of an increased proportion of silicon dioxide (SiO₂) and boric anhydride (B₂O₃) and is used in the glass container sector primarily where sensitive or aggressive contents must be packaged safely and durably—for example, in the pharmaceutical industry, in laboratories, or for heat-resistant food storage containers.

Typical applications include medicine vials, ampoules, syringe barrels, test tubes, as well as heat-resistant preserving jars or special packaging for sensitive cosmetics. The glass is neutral in taste, inert, sterilizable, and resistant to chemicals and thermal stress.

Compared to borosilicate glass for technical applications, the composition in the container glass sector is slightly adjusted: The boron content is somewhat lower to allow for better formability in industrial production lines. Compared to tableware borosilicate, the focus is more on sterilizability, break resistance during transport, and mass processability – less on optical brilliance or design.

Manufacturing process of borosilicate glass for glass containers:

Production takes place at high temperatures (up to 1,600 °C) in melting furnaces designed for the tough, difficult-to-form borosilicate mass. The material is usually processed using tube glass methods, press-and-blow techniques, or segmented molds for small-volume containers. The goal is to produce a high-purity, low-stress glass mass with the lowest possible thermal expansion – important for applications where the containers must be autoclaved, sterilized, or heated.

Opal glass – also known as milk glass – combines a functional light-protective effect with a high-quality, brand-defining appearance. It is preferably used in the cosmetics, food, and pharmaceutical industries when light-sensitive products such as creams, syrups, or milk need to be both protected and attractively packaged.

Typical applications include cream jars, medicine vials, perfume bottles, or milk bottles. The translucent, usually glossy white surface protects the contents from UV radiation and gives the product a sophisticated, recognizable appearance.

Difference to opal glass for tableware:

In contrast to opal glass used in the kitchen, which is designed for thermal stress (e.g., dishwasher, oven) and mechanical robustness, the focus in the container sector is clearly on light protection, thin walls, and decorative design possibilities. The formula is therefore balanced differently – in favor of formability and design, less for heat resistance in everyday use.

Special features in the manufacturing process of opal glass as container glass:

The typical opacity is created by adding opacifying agents such as fluorides or phosphates. During controlled cooling, these form micro-fine crystals that scatter the light and create the characteristic milk glass effect. For a uniform, color-stable surface, precise temperature control throughout the entire melting and cooling process is essential. Even small deviations can impair the optical quality. For brand presentation, opal glass is additionally refined with screen printing, embossing, metallic, or color effects – often in combination with custom shapes for high recognition value.