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[Evonik] A registered trademark for an ultra-fine powdered Silica that was first made in 1942 at Degussa. Aerosil® is a colloidal form of silica that is a very light and fluffy powder. It is made by burning silicon tetrachloride in a hydrogen-oxygen furnace. This produces spherical particles; the particle size can be controlled and varying grades are available ranging in size from 4 to 25 micrometers. The fine particle size provides a high surface area ranging from 35-410 m2/g. Traditional Aerosil® particles (e.g. Aerosil® 300) are hydrophilic and can adsorb water up to 40% of their own weight while still performing as a powder. It is used as a filler, thickener, and as a matting agent in paints. There is also a modified version of Aerosil® (e.g. Aerosil® R7200) that is hydrophopic. It can be added to an aqueous solutions without changing its viscosity. Its water-repellant properties are used to improve corrosion protection of some coatings.

Examples of labeling of Aerosil include:

  • Aerosil® 90-380: hydrophilic, fumed SiO2
  • Aerosil® R972-R9200: hydrophobic, fumed SiO2 with 0.6-6.5% carbon
  • Aerosil® MOX: mixture of SiO2 and Al2O3 used in low viscosity aqueous dispersions
  • Aerosil® COK 84: mixture of SiO2 and Al2O3 used to thicken aqueous media

Synonyms and Related Terms

aerosol silica; amorphous fumed silica; hydrophilic silica; fumed silica gel


  • Thickener without opacification
  • Defoamer
  • Sorbent

Personal Risks

  • Inhalation may cause silicosis; use dust mask.
  • Particles can irritate eyes.
  • CDH Fine Chemical SDS

Collection Risks

  • Non-flammable.
  • Inert.

Physical and Chemical Properties

  • pH = 3.6-4.5
  • CAS = 112945-52-5
  • Melting Point = 1700 C
  • Density = about 2.2 g/ml
  • Refractive Index = 1.45

Resources and Citations

  • Evonik: History of Aerosil
  • Evonik: Aerosil brochure
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 709
  • Ceramics and Glass Conservation Section, List of Workshop Materials, The British Museum, London
  • MSDS Sheet at MFA: old CAS# = 68611-44-9