Abstract: The invention provides a method for the production of a stable monolith, the method comprising the encapsulation of a waste material in the monolith by means of chemical bond formation within the monolith, and a method for the disposal and storage of waste materials, which comprises the production of a stable monolith by such method. Waste materials which are particularly suited to treatment according to the invention include various geopolymer precursors, most particularly ion exchange materials such as aluminosilicate materials, and the invention is particularly suited to the disposal and long term storage of radioactive waste materials.