White Sapphire®: The SPF Boost Every Formulator Should Know About

If you're formulating with zinc oxide, White Sapphire can push your SPF higher without increasing your zinc concentration. Here's how it works.

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The SPF Boosting Mechanism

White Sapphire increases diffuse light transmittance through the formulation. Diffuse transmittance scatters light in multiple directions rather than allowing it to pass straight through. In a sunscreen formulation, this increases the path length of UV photons through the product, giving the zinc oxide active more opportunity to intercept and absorb or scatter them before they reach the skin.

White Sapphire does not absorb UV radiation directly. Its role is to increase the optical density of the formulation matrix in a way that supports the zinc oxide active. This effect is supported by a provisional patent covering the combination of White Sapphire with ZinClear XP zinc oxide in sunscreen and cosmetic formulations.

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Performance in a Finished Sunscreen

The SPF boosting capability has been demonstrated in an SPF 50+ sunscreen incorporating White Sapphire alongside zinc oxide. That formulation also demonstrates anti-sweat performance, a result of White Sapphire's oil and sebum absorption capability, which reduces surface tackiness and breakdown in high-zinc-oxide systems under heat and activity.

White Sapphire therefore contributes to the formulation in two ways simultaneously: it supports SPF output and improves the sensory and wear profile of the finished product. These are typically competing requirements in mineral sunscreen formulation.

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What This Means for Formulators

Including White Sapphire in a mineral sunscreen formulation can deliver SPF performance above what the zinc oxide concentration alone would achieve, while improving finish, feel, and wear. In systems where the zinc oxide load is already at or near the upper aesthetic limit, this is a meaningful capability.

Both Matte and Glow variants carry the SPF boosting capability. Matte is the stronger choice in dry-touch sunscreen systems where oil control and anti-sweat performance are primary requirements. Glow suits tinted SPF and complexion-sunscreen hybrids where optical finish quality is part of the product proposition. Typical inclusion levels sit between 2% and 10%. Both variants are ECOCERT COSMOS Version 4 certified.

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Technical Summary

White Sapphire is an inorganic mineral ingredient (INCI: Alumina or Synthetic Sapphire, CAS 1344-28-1) composed of aluminium oxide at greater than 99.5% purity with a hexagonal crystal structure. Both Matte and Glow variants are ECOCERT COSMOS Version 4 certified (COSMOS-standard AISBL, 2023) and listed by the U.S. FDA as a colour additive exempt from certification under 21 CFR 73.1010 (U.S. Food and Drug Administration, 2024).

SPF-boosting activity in combination with ZinClear XP zinc oxide is covered under a provisional patent held by Advance ZincTek. The mechanism operates through increased diffuse light transmittance in the formulation matrix, extending the effective path length of UV photons and supporting the absorbing and scattering behaviour of the zinc oxide active. Application in a demonstrated SPF 50+ formulation with anti-sweat performance has been documented. The influence of secondary scattering materials on SPF output in mineral sunscreen systems is consistent with established photophysical principles governing light interaction in particulate systems (Diffey & Robson, 1989).

Zinc oxide is recognised as a Category I UV filter by the U.S. FDA under the OTC sunscreen monograph, and is approved as a UV filter in Australia under the TGA's listed medicines framework (U.S. Food and Drug Administration, 2021; Therapeutic Goods Administration, 2023).

Key physical parameters: BET surface area 4 to 7.5 m²/g; oil absorption 50 to 100 g/100g; mean particle size 6.0 to 11.0 µm (Matte) and 4.0 to 12.0 µm (Glow); coefficient of friction 0.25 to 0.35. Neither variant is classified as carcinogenic, mutagenic, or a specific target organ toxicant. Non-nano aluminium oxide is not considered to be dermally absorbed through intact skin (Scientific Committee on Consumer Safety, 2014).

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References

COSMOS-standard AISBL. (2023). COSMOS standard Version 4: Technical guide for cosmetic products. https://cosmos-standard.org/the-cosmos-standard/

Diffey, B.L., & Robson, J. (1989). A new substrate to measure sunscreen protection factors throughout the ultraviolet spectrum. Journal of the Society of Cosmetic Chemists, 40(2), 127–133.

Scientific Committee on Consumer Safety. (2014). Opinion on the safety of aluminium in cosmetic products (SCCS/1525/14). European Commission. https://ec.europa.eu/health/scientific_committees/consumer_safety/docs/sccs_o_153.pdf

Therapeutic Goods Administration. (2023). Safe use of sunscreens. Australian Government Department of Health. https://www.tga.gov.au/resources/explore-topic/sunscreens/safe-use-sunscreens

U.S. Food and Drug Administration. (2021). Sunscreen drug products for over-the-counter human use: Proposed administrative order. https://www.federalregister.gov/documents/2021/09/27/2021-20780/amending-over-the-counter-monograph-m020-sunscreen-drug-products-for-over-the-counter-use-over

U.S. Food and Drug Administration. (2024). Code of Federal Regulations, Title 21, §73.1010: Alumina. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-A/part-73/subpart-A/section-73.1010