Examples include silica gel, fumed silica, talc, and magnesium carbonate. Notable examples include fused quartz, fumed silica, silica gel, and aerogels. Examples of glidants include magnesium stearate, fumed silica (colloidal silicon dioxide), starch and talc. Silicon tetrachloride can also be hydrolysed to fumed silica. Fumed silica has a very strong thickening effect. Fumed silica is commonly used as a rheology agent to make otherwise low-viscous fluids thixotropic. Fires represent particularly complex reactions and can produce pigments, cement, fumed silica etc. Fumed silica is used as a bulking agent for thicker coatings of the material. Fumed colloidal silica can be added to help with the workability of the resin. Aggregated fumed silica can be applied to large surfaces to render them hydrophobic. Most commonly, the silicone oil is polydimethylsiloxane (PDMS) and the thickener is amorphous fumed silica. It is less pure than fumed silica and should not be confused with that product. Fumed silica is not listed as a carcinogen by OSHA, IARC, or NTP. It is sometimes confused with fumed silica (also known as pyrogenic silica, CAS number 112945-52-5). Fumed oak is also called smoked oak.