Production Process
Formula has decades of experience in producing quality plaster and gypsum products from high purity gypsum.
By directly controlling and finely tuning the extraction and production process, Formula adapts the structure and properties of plaster formulations, to match the needs of a variety of highly technical industries.
Extraction
Gypsum is extracted from open air or underground mines, using specific drilling machinery and non-polluting explosives. Rock size may reach up to 50 cm in diameter.
Crushing
Primary crushing aimed at reducing rocks to a size of less than 10cm, subsequently easier to handle, is carried out in the quarry or at the entrance to the plaster manufacturing station.
Storage
Rock that has undergone primary crushing is stored to ensure production continuity, and optimal homogeneity between rock extraction batches.
Sifting
It is necessary to separate and control gypsum particle size in order to obtain the exact product properties required for the plaster being manufactured.
Calcination
Calcium sulphate hemihydrate (CaSO4.½H2O) or plaster is obtained through the partial or total dehydration of gypsum at a temperature ranging from 120° to 400° C The structure and properties of the final product are directly dependent on the chosen calcination conditions (temperature, pressure, rapidity).
Several calcination processes exist:
Beta Process
During the calcination process, under regular environmental pressure, dehydration water evaporates and a micro-porous structure is formed. Beta plaster crystals have a high specific surface and high water demands. Beta plasters casts have high porosity, but low mechanical properties and are therefore used for example in lightweight building applications or moulds in ceramic applications for their absorbent properties.
Alpha Process
Alpha type plaster is used mainly in industrial plaster formulations for its high mechanical strength.
This plaster type is a compact crystal with a low specific surface and low water demands to produce hard, low porosity casts. Alpha plaster can be formed through 2 different production procedures
Dry process: steam vapour is injected during calcination. The plaster is dried and treated.
Wet process: calcination of a gypsum slurry under pressure. The plaster is then dried.
Grinding
Following the calcination process, the plaster is ground to obtain a powder. Particle size distribution is an important factor in the product properties
Mixing & Blending
Often different plasters will be blended to combine their properties and optimise product solutions to suit market requirements. With the plaster in finely ground form, the final mixing stage is possible. A choice of additives will finely tune the products properties to match the customer’s needs, in terms of setting time, viscosity, porosity, colour, mechanical strength…
Testing
Laboratory testing is carried out at several production phases, to ensure all products meet the strict product specifications before being bagged and shipped.
Packaging
Feasibility studies are carried out to ensure the packaging item chosen for each product gives optimal protection and guarantees the product quality all the way to the end-user.