Inorganic Sunscreen FAQ

ZnO for UVA coverage and TiO2 for UVB and the higher refractive efficiency; many serious formulas use both.

ZnO has a wider absorption band that extends further into UVA, which is why it appears in products making a broad-spectrum claim on an inorganic-only basis. TiO2 scatters more efficiently per unit mass and gives better SPF for the same loading, but its coverage falls off in the UVA region. Blending them lets you hit both ends without pushing either to a loading that ruins the texture.

In practice, an inorganic-only broad-spectrum formula is usually a blend. A single-filter formula is usually ZnO for UVA or TiO2 for SPF.

It is the single most consequential decision in an inorganic sunscreen, because nano status changes the notification route, the labelling and the safety dossier.

Most markets define nano by primary particle size below 100 nm. Above that threshold the material is treated as a conventional pigment; below it, additional requirements usually apply — a specific notification, a safety assessment on the nano form, and in some markets specific labelling. The definitions are not identical between markets, and a material that is non-nano in one may be nano in another.

Our sunscreen range is nano by design (15–160 nm), and our pigment TiO2 range is non-nano. Tell us the destination market at enquiry and we will identify which documents that market requires for the nano form.

Smaller particles give more transparency and better SPF per unit mass; larger ones give less whitening but require more loading, and above a certain size the UV performance starts to drop.

15 nm (N15E, 4015) is the transparency grade — the film is nearly invisible on skin, which is what makes a high-SPF mineral sunscreen cosmetically acceptable. 30 nm (23M, N30E, S30W, S25W) is the balance point most formulas use. 50 nm (N20E, 4513, 4528) and 80 nm (N80E AS) trade a little transparency for lower viscosity and easier dispersion. 160 nm (Kingruti 160 AS) is at the edge of the UV absorption range and is used where feel matters more than SPF efficiency.

One caveat: the optimum for UV attenuation is around half the wavelength being blocked, so the smallest particle is not automatically the most efficient performer. It is the most transparent, which is a different thing.

Pre-dispersion if you can — it solves the hardest problem in the formula, which is wetting a nano powder completely.

Nano powders have enormous surface area and agglomerate readily; getting them fully dispersed in your own process usually needs specialist equipment and a lot of time, and any agglomerate left is both a whitening defect and an SPF loss. A pre-dispersion arrives already dispersed at a known solids content, so you are adding a liquid rather than a powder.

Choose powder only if your process already handles nano dispersion well, or if the carrier of the available dispersions is incompatible with your system.

Match it to your emollient system and to the feel you want — the carrier becomes part of the formula.

C12-15 alkyl benzoate (4015, 4513, 4560, Z-6060) is the general-purpose choice: light, dry, widely compatible. Dimethicone (2355, Z-6050) suits silicone-heavy and W/Si systems. Dicaprylyl carbonate (4528) gives a slightly drier, more elegant feel. Water and glycerin (5030) is for aqueous systems and gels.

The solids content also varies by carrier — 40% for the finer 15 nm material, up to 65% for the 30 nm grades in a light ester. Check the delivered solids against your target loading before you fix the percentage in the formula.

As a rough starting point, 5–10% combined inorganic solids gets you into the moderate-SPF range, and 15–25% is where mineral-only high-SPF formulas live — but the number that matters is measured in your own base, not calculated.

SPF depends on the film thickness, the dispersion quality, the presence of other filters and the base itself. Two formulas with identical filter loading can differ by several SPF points because of dispersion alone. That is why the pre-dispersion route often outperforms a powder route at the same nominal loading.

Test in vivo for the claim, and use in vitro for development iterations. Do not specify an SPF from a loading table.

Yes — it is the main lever you have over the photocatalytic activity of the particle.

TiO2 and ZnO generate reactive species at the surface when they absorb UV, and those species attack the surrounding formula: fragrances fade, colours shift, emollients oxidise. An alumina or silica coating, or a silane treatment, passivates the surface and suppresses that activity. It also reduces the interaction between the mineral filter and organic filters in the same formula, which is where a lot of the instability in mixed systems comes from.

All our sunscreen grades carry a coating for this reason. If you are formulating with organic filters alongside, the coated grades are the safer choice.

Smaller particle size, better dispersion, and if necessary a lower loading with an organic filter carrying the rest of the SPF.

White cast has two causes. Undispersed agglomerates scatter visible light strongly and look like a chalky film; and larger particles scatter visible light by design. So the first fix is dispersion — a pre-dispersion at 15–30 nm usually removes most of the cast without changing the loading. The second is size: moving from 80 nm to 15 nm reduces the visible scatter substantially.

If the cast persists at the SPF you need, the honest answer is that a mineral-only high-SPF product will have some cast on deep skin tones, and the formulation route is to blend with an organic filter rather than to keep reducing the particle size, which costs you UV efficiency.

We provide the material documentation: COA, TDS, SDS, and the nano-specific statements a market may require. The finished-product testing — SPF, UVA-PF, critical wavelength, water resistance — is done on your formula, not on the raw material.

What we can support with is application data: dispersion guidance, recommended starting loadings, and the coating information you need for your safety assessment. For an in vitro SPF iteration we can tell you what has worked in comparable systems, but the number has to come from your own test.

If you need a specific market's nano notification supported, tell us the market and the product category at enquiry — the document set differs and it is better to assemble it before the launch date than after.

MOQ is 1 kg for a powder sample and 5 kg for a pre-dispersion sample; production quantities start at 25 kg. Lead time is 7–15 working days for stock grades, longer for a custom carrier.

Because nano materials attract more documentation, allow extra time before a first shipment into a new market. Samples ship with COA, TDS and SDS, and with the particle size data you will need for the nano assessment.

Store sealed at 15–30 °C. Pre-dispersions should be rolled before use, as the solids settle.