A type of shale-inhibitive water mud that contains sodium or potassium silicate as the inhibitive component. High pH is a necessary characteristic of silicate muds to control the amount and type of polysilicates that are formed. Mud pH is controlled by addition of NaOH (or KOH) and the appropriate silicate solution. Silicate anions and colloidal silica gel combine to stabilize the wellbore by sealing microfractures, forming a silica layer on shales and possibly acting as an osmotic membrane, which can produce in-gauge holes through troublesome shale sections that otherwise might require an oil mud. Mud containing up to 50 vol. % soluble sodium silicate was first used in the 1930s for control of shale but suffered from gelation problems. In the 1990s, silicate muds were reintroduced as a way to avoid using oil muds. The newer systems use lower silicate concentrations and KCl or NaCl or both to contribute to shale control. This comeback may succeed due to better solids control and proper use of silicate chemistry. Poor lubricity and temperature tolerance are the main drawbacks.