Glass is an environmentally-friendly product used for building, packaging and technology. It is made from silica sand, soda ash and limestone and/or dolomite. The oxides from these natural minerals form the glass, solidify it and enhance its major chemical and physical properties.

Limestone and dolomite provide the necessary CaO component for glass by working as a network modifier. MgO from dolomite- or dolime-based products offers further advantages during the melting process. It also adds properties such as reduced melt viscosity, avoidance of crystallization and physical resistance. Lhoist supplies the glass industry with dedicated pure dolomite and limestone products of very consistent chemical composition and particle size under the Visucal® brand. These minerals and the oxides from them along with CaO special products are used for the production of different types of glass. Another of our lime products, Sorbacal®, is very efficient for Flue Gas Treatment installations on glass manufacturing facilities.

Float glass

Float glass is a mechanically stable glass that can be cut and handled with little breakage. It is most commonly used for building, automotive and solar-energy applications. It is made via float processes. The base network modifier function of CaO and MgO is complemented by the up to 5% share of magnesium oxide. Magnesium oxide is supplied by dolomite and offers a wider processing temperature range, reduced batch melting temperatures and improved fining conditions. Dolomite acts as a stabilizer contributing to a smooth and safe float glass production process. It also improves glass’s general resistance to natural or chemical attack.

Container glass

Container glass has industrial uses as well as being found in everyday applications, such as food containers, pharmaceutical and cosmetic bottles, water/wine bottles and the glasses from which we drink.

Limestone, silica and soda ash are the three base batch ingredients for this type of glass. Controlled iron oxide content and adjusted granulometry of the limestone product offer consistent quality. Adding adjusted amounts of dolomite helps suppress crystallization, lower soda ash demand and improve fining conditions. As a source of calcium and magnesium, dolomite also acts as a fluxing agent and stabilizer.

Continuous glass fiber filaments

Continuous glass fiber filaments are converted into other products, the end use of which is generally the reinforcement of composite materials, such as thermosetting resins and thermoplastics. The production of continuous glass fiber filaments requires consistent highest quality fibers, as well as uniform glass, manufactured from the most homogeneous and pure raw materials. Fine-milled limestone, dolomite and specially fine-milled lime are standard products for E-glass and ECR (E-Glass Chemical Resistant) fiber glass. Fine-milled CaO is ideal for melting furnaces that must be able to increase capacity or that have energy limitations. In full electrical furnaces, burnt lime and dolime products prevent the formation of CO2 on insulation layers and hot breakthrough in the batch blanket. Our kaolin products are also used in fiberglass as a source of alumina.

Glass fibers for insulation

Glass, mineral and stone wool are considered safe, fireproof and well-suited insulation materials for the preservation of energy (cooling and heating) and noise isolation. The largest components are silica sand and glass cullet. Glass wool is produced either by blowing high-pressure air through a stream of molten glass or by spinning it ‘cotton candy’ style. Limestone and dolomite contribute CaO and/or MgO to adjust chemical composition. They are also required for their melting and physical properties. Our dolomitic lime, dolomite and high-calcium limestone products also serve as fluxing and stabilizing agents. Alkali earth oxides CaO and MgO increase the surface tension of the glass and have a positive impact on the resulting glass wool.

Technical glass

Technical glass includes products such as glass for TV screens and computer monitors, lighting glass (tubes and bulbs), optical glass, laboratory and technical glassware, borosilicate and ceramic glass (cookware and high temperature domestic applications), and glass for the electronics industry (LCD panels). CaO and MgO play a small but important role as other glass-forming oxides are generally used (boron, alumina, etc.). We provide consistent and homogeneous Visucal® limestone and dolomite to help ensure the production of excellent quality technical glass (smart phones, TVs, tablets, etc.).