The porous mass production process is as follows:

• recording data from the cylinder (number, weight, capacity)
• preparation of mass (mixture of water, lime, silica, carbon fibre)
• filling of the cylinder with a fluid paste of mass
• heating in the furnace under pressure; reaction between lime and silica with the formation of calcium silicates (xonolite, tobermorite)
• oven drying, with the elimination of water remaining in the porous mass
• inspection and quality control
• sand-blasting and painting of the outside surface of the cylinder
• fitting of the valve
• solvent addition subject to removal of residual air from the cylinder
• introduction of acetylene to saturation
• packaging and despatch.

SIAD AF porous mass is produced in the Osio Sopra production plant, by a dedicated division. Its production capacity is about 50 000 cylinders per year.