Sodium silicate
![Expantrol proprietary sodium silicate suspended in about a 6.5-mm-thick layer of red rubber, type 3M FS195, inserted into a metal pipe, then heated, to demonstrate hard char intumescence, strong enough to shut a melting plastic pipe](/Images/godic/202502/11/Fs1955926.jpg")
![Palusol-based intumescent plastic pipe device used for commercial firestopping](/Images/godic/202502/11/Palusolmanschette5926.jpg")
![World War I poster suggesting the use of waterglass to preserve eggs (lower right).](/Images/godic/202502/11/lossy-page1-170px-Raise_More_Poultry...on_Farms_and_Back_Yards...More_Eggs_and_Poultry_Will_save_Beef_and_Pork._-_NARA_-_512571.tif5926.jpg")
Sodium silicate is the common name for compounds with the formula Na2(SiO2)nO. A well-known member of this series is sodium metasilicate, Na2SiO3. Also known as waterglass or liquid glass, these materials are available in aqueous solution and in solid form. The pure compositions are colourless or white, but commercial samples are often greenish or blue owing to the presence of iron-containing impurities.