Al2O.2H2O.SiO2 Most plastic and impermeable common clay materials. It binds particles together making bodies stronger in the green and dry state. Its' minute particles fill voids between others to produce a more dense mass. Adding bentonite to glazes imparts better dry strength and a harder more durable surface. 1 part bentonite can plasticize 10 parts of kaolin. Bentonite bodies are stronger but dry slower, crack more and fire darker with potential iron specks. 1-2% bentonite added to the dry powder can greatly improve glaze suspension. Bentonite containing clay bodies may look dry but may not be - they must be very slowly dried to prevent steam being produced and creating cracks. Make into a paste before adding to glaze batches if not added dry to the powder.
Glass jar is for illustration purposes only.