The sealing materials carrying the Doniflex® trademark are made according to the "Beater addition" process. Under the influence of chemical and physical interactions fibers, fillers, binders and different additives are formed in flocs in water suspension and are applied to a sieve, where by dewatering, pressing and drying, layer of sealing material is formed. This environment friendly manufacturing process allows the production of sealing materials with high compressibility and homogenous structure. The density of the layer produced according to this process can be, if required, increased by subsequent pressing and additionally coated with different anti-stick coatings to meet the specific application requirements.