1. n. 
A type of mud that contains the three components that form a chemical buffer, whether by design or by coincidence. Buffering results from components that react with the added OH- ions (or added H+ ions) forming slightly soluble or slightly ionized compounds. Water is one component of a buffer and various ions are the other components, such as bicarbonates, carbonates, lignite, lignosulfonate, silicate and sulfide. Clay solids are buffers because of their ability to accept or donate H+ ions on their surface. The pH of a buffered mud will not increase as fast as expected after addition of caustic soda, for example.