Manufacturing Process

Gypsum is made from:

• natural gypsum, sedimentary rock extracted from mines or underground quarries,
• synthetic gypsum, produced from by-products of energy generation or industrial waste.

Making gypsum from natural gypsum involves crushing and grinding the gypsum mineral, then firing it at 150°C. Additives can be mixed with the gypsum in very small quantities:

• starch improves the adhesion between the gypsum and the paper in plasterboard production,
• retarding agents slow the setting time of gypsum.

Manufacturing plasterboard:

Plasterboard is made up of a thin core of gypsum between 2 sheets of paper. Its manufacture involves several steps:

• the gypsum is mixed with water. Various solid and liquid admixtures are introduced until a homogeneous slurry is obtained,
• 2 layers of paper are continuously unrolled, 1 below and 1 above the mixer. The edges of the upper paper layer are glued to the edges of the lower layer. The sandwich then passes through a system of rollers that compresses it to the desired thickness,
• after drying, the sheets are cut into standard lengths,
• they are then stored, ready to be shipped to building sites.

Supervised manufacturing

Drying time

Extensive R&D programs have been devoted to drying as this stage has an impact on the quality of the finished product.

The drying time must be uniform and very precise:

• sheets containing too much moisture cannot be stored properly,
• "burned" sheets lose their mechanical strength because the paper and the gypsum tend to come apart.