A process that occurs with the intimate blending of fine-grained materials (commonly clays and/or organic material) with medicinal mineral water or sea water for variable periods of ageing. Biological activity during maturation may play a role in enhancing healing properties and in shortening ageing time. Cation exchange between minerals and water may also occur during maturation, affecting the fluid chemistry, and this may enhance the physical properties (e.g. plasticity) of the suspensions.