Cristobalite

Cristobalite (silica, chemical formula SiO₂) is the result of the calcination of quartz at a temperature of 1500°C:

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Cristobalite can be characterised by:

• High brightness
• Relatively high Mohs hardness of 6.5
• Relatively low refractive index, making it a transparent filler in various binders
• Easy wetting
• High inertness in various media
• Transparency for UV-radiation (ie. suitable for UV-curing processes).

Note when using cristobalite: depending on the particle size distribution of the product, it can be labelled (STOT RE 2 or STOT RE 1). For more detailed information, visit www.safesilica.eu.

Basic properties

Product overview

(1): Tamisé: > 500 µm = < 1%

Production locations Sibelite

Sibelite is the brand name for Sibelco’s cristobalite products.

The majority of the fine grades are labelled STOT RE 2 or STOT RE 1 due to the presence of fine crystalline silica.

Benefits

• Dirt pick-up resistance: the presence of cristobalite improves the coating’s resistance to dirt (from the atmosphere, for instance).
• Ease of tinting: due to the combination of refractive index, brightness and colour, paints including cristobalite will provide excellent reproducible colour results when working with tinting systems.
• Texture effect: the use of coarse cristobalite grades provide texture to the coating surface.
• Tint retention: paints including cristobalite show improved tint retention over other minerals when subjected to natural weathering.
• UV resistance and weatherability: due to its inertness, cristobalite supports good UV and weatherability performance to exterior architectural coatings.
• Burnish resistance: due to its hardness of 6.5 on Mohs scale, cristobalite provides good burnish resistance (low tendency to become glossy when rubbed).
• Gloss control: the gloss level of an interior coating can be regulated by selecting the appropriate grade of cristobalite.
• Scrub resistance: due to its hardness of 6.5 on Mohs scale, cristobalite improves the wet-scrub resistance of interior decorative paints.
• Stain resistance: cristobalite acts as a supporting mineral filler in stain resistant coatings.
• Abrasion and scratch resistance: due to its fairly high hardness of 6.5 on Mohs scale, cristobalite provides abrasion and scratch resistance to the coating.
• Chemical resistance: due to its inert nature, cristobalite  provides good chemical resistance compared to conventional fillers.
• Clarity: due to its fairly low refractive index, cristobalite becomes transparent when combined with certain binder systems.
• UV-curing compatibility: being transparent for UV radiation, cristobalite does not block the curing mechanism.
• Brightness: being one of the fillers with the highest brightness, cristobalite contributes to the visibility of road marking paints.
• Skid resistance: coarse cristobalite grades will give a roughness to the substrate, making it less slippery in general as well as in wet conditions, and provides better visibility in wet conditions.
• IR reflection: cristobalite contributes to IR reflection of roof coatings.
• Pore and grain filling properties (sealer): with low impact on the viscosity, cristobalite can be used as a mineral filler in sealers to give them more body.