The role of lime in glass production

Glass is primarily made from silica sand (SiO₂), soda ash (Na2O) and limestone (CaO), but its final properties such as durability and transparency, depend on the addition of other raw materials. Lime-based materials such as limestone (CaCO₃), quicklime (CaO), and dolomite (CaMg(CO₃)₂), plays a vital role in modifying and stabilizing the chemical structure of glass and enhancing its performance. 

Lime-based materials act as fluxing agents during the melting process, helping to lower the melting temperature of the raw materials. This reduces energy consumption and improves furnace efficiency. It enhances chemical stability by preventing crystallization during production. It also increases resistance to weathering and corrosion, ensuring a long lifespan. 

In addition, lime products improve the mechanical strength and hardness of glass products, which is essential for applications ranging from flat glass and containers to fiberglass and specialty technical glass. 

Depending on the type of glass being produced, manufacturers may use different lime-based materials: µ

• Flat glass (used in windows and automotive applications) benefits from high-purity limestone and dolomite or their burnt forms to ensure optical transparency and chemical durability. 

• Container glass (bottles and jars) requires limestone or lime to control viscosity during melting and forming, and to ensure chemical durability. 

• Fiberglass production uses limestone and dolomite, or their burnt forms, to control viscosity during melting and forming, while enhancing fiber durability and integrity. 

• Technical glass (used in electronics or labware) demands precise control over composition, where lime-based products help to fine-tune melting behavior and stability. 

Under the Visucal^® brand, Lhoist offers specialized solutions developed for the glass industry, ensuring optimal transparency, durability, and process efficiency. Combined with technical support and process expertise, Visucal^® helps manufacturers meet demanding production standards while improving sustainability and cost-effectiveness. 

Why is dolomite used in glass manufacturing? 

Dolomite provides both calcium and magnesium oxides, which help improve chemical durability. It also acts as a fluxing agent, lowering the melting temperature of raw materials and enhancing energy efficiency during production. In applications like flat glass and fiberglass, dolomite contributes to improved chemical and mechanical strength. 

What is the difference between float glass and normal glass? 

All types of glass such as container glass or pressed glass can be considered “normal,” but the differences lie in how it is made and used. They can vary in thickness, texture, and optical properties depending on the manufacturing process. 
If we focus on float glass, it is produced by floating molten glass on liquid tin, resulting in a perfectly flat and uniform surface. It is commonly used in windows, mirrors, architectural and automotive applications 

What types of lime are used in glass manufacturing? 

Glass producers typically use high-purity limestone, quicklime (CaO), dolomite, and dolime depending on the type of glass and desired properties. These materials help control melting behavior, improve chemical stability, and enhance the mechanical strength of the final product. 

How do lime-based products affect the transparency of glass? 

Lime, dolime and minerals products contribute to the optical transparency of glass thanks to their low level of impurities, mainly iron oxide. High-purity lime products like those in Lhoist’s Visucal^® range are specifically selected to minimize coloration and ensure consistent light transmission in flat and container glass.