How Stone Wool is made

How Glass Wool is made

Inputs

The required amounts of raw material are measured and sent to a melting furnace. For stone wool this is the rock or recycled material plus energy. Manufacturers are working hard to increase the recycled content of mineral wool whilst maintaining the high quality of their product.

For glass wool the raw materials are sand, limestone and soda ash, as well as recycled off cuts from the production process. Recycled window, automotive or bottle glass is increasingly used in the manufacture of glass wool and it now accounts for 30% to 60% of the raw material input. In some plants this is as high as 80%.

The reuse of off cuts and recycled materials has helped to steadily reduce the energy input required to produce mineral wool.

Furnace

The raw materials are melted in a furnace at very high temperatures, typically 1300°C to 1500°C.

The smoke that is created during this process is filtered and flue gases cleaned to minimise any environmental impact.

Spinning

After the furnace droplets of the vitreous melt are spun into fibres, droplets fall onto rapidly rotating flywheels or the mixture is drawn through tiny holes in rapidly rotating spinners. This shapes it into fibres.

Binding

Small quantities of binding agents are added to the fibres. The structure and density of the product can be adapted to its precise final usage.

Curing

This is then cured at around 200°C.

Cutting

The mineral wool is sawn to the required size and shape, for example into rolls, batts, boards or it is customised for addition to other products. Off-cuts and other mineral wool scraps are recycled back into the production process.

Packaging

Due to its impressive elasticity, mineral wool can be compressed to reduce its volume during packaging, making it cheaper and easier to transport and handle.

Gases and waste

Waste such as off-cuts are recycled into the production process reducing inputs and energy requirements.

Gases from the production processes are cleaned in filters and after-burners to minimise impact on the environment.