Is my non-nano TiO2 filter really not nano? And how can I know this and measure it with certainty?
As the cosmetics industry moves closer to the date of 2023 in the United States where only GRASE-approved mineral filters will be accepted in sun care products, many customers are trapped between regulations and charters. This need to know more about mineral filter formulations by January 2023 explains the frequency with which a particular question arises: how can we know for sure whether the filters that will be used in the formulations are nanometric or not ? (between 1 nm and 100 nm for primary crystals)
In short, “nano or not nano, that is the question of the moment.”
Formulators wonder how to know if the pigment crystals used are below 100 nm or not.
A valid and real visual solution is to magnify up to 200,000 times with a good and modern TEM (Transmission Electron Microscope) microscope. This will give you a transmission image of the actual size of the crystals and agglomerates in your formulas. As the surface charges of these crystals are very high, they are always agglomerated. Often, this solution is performed by an external laboratory and therefore has a cost for each batch you make of your formulas.
A TEM microscope allows you to see images where the electron passes through the crystal, unlike the SEM (Scanning Electron Microscope) microscope where the electron bounces off the crystal. With the TEM, you see the crystals in black and the SEM in white.
At The Innovation Company® we offer a simpler and probably more useful and interesting solution, based on the Critical Wavelength of the dispersion or the actual final formula, using your minerals.
Indeed, the Critical Wavelength gives a good idea of the real protection at 90% of the nanometric wavelength. In most regulations around the world, a minimal Critical Wavelength of 370 nm is required to achieve an SPF value. If the value is below this, you will not get an SPF, and therefore the authorization to market your formula, because it will not validate all the criteria. Of course, this can only be done with a UV spectrophotometer with a high absorption power (preferably level 3).
If we take a closer look, around 20% of the products currently on the market do not even meet this simple criterion, being above MCW (Minimal Critical Wavelength of 370 nm).
For example, a TiO2 primary crystal of 14/16 nm typically gives a reading of approximately 364/366 nm MCW. By proceeding this way, you already know that they are nanocrystals. You know the CW of this type of crystal and you know the size of your mineral filter.
These 14/16 nm primary crystals are below the MCW level required for validation and show SPF failure. The most widely used TiO2 in the C&T market, is a 14/16 nm primary crystal. Hence the large number of observed products that do not meet the criteria, unless they have added organic filters, which will no longer be approved in 2023.
If a Zinc Oxide crystal is too transparent, and therefore close to a primary crystal of 20 nm and less, it will not reach this MCW 370 nm passage level either.
Today, many suppliers have showed and shared PSD (particle size distribution) graphs of their mixtures, all showing a PSD size greater than 1 micron. These suppliers have been claiming for years that they use filters that are not nano filters! In reality, however, they are of course nano-crystal sized when you measure the Minimal Critical Wavelength….
The Cosmos and Ecocert organisations, as well as many Vegan Charters, and the latest Clean charters, have approved these PSD data. But the PSD method doesn’t really show MCW, you only measure agglomerates, not crystals.
These suppliers are therefore either incompetent or they are taking advantage of a marketing ploy to sell mineral UV filters at higher prices. And this is not good for either credibility or consumer ethics.
We know the critical wavelength of each crystal size in Zinc Oxide or Tio2.
This leads us to think that some suppliers make the graphics say what they want to see or not.
At The Innovation Company®, we’re not here to blame consumers (who think nano filters are dangerous and penetrate the skin barrier), nor are we here to blame suppliers (who are trying to make marketing happy, who want to sell to consumers with fears, not knowledge).
These inaccurate statements do not help consumers achieve the highest levels of safety when it comes to minerals, because organic filters with very low molecular weight actually diffuse into the skin in 10 seconds….
How will you know now, if you don’t have a spectrophotometer?
Simply send us your formula to measure Critical Wavelength and we’ll see where it is.
For your information, pigmentary crystals larger than 100 nm, if they are indeed larger (210 to 300 nm), will give you a Critical Wavelength of above 387 nm, and are extremely white on your skin.
So can you filter UV rays with non-nano crystals of TiO2 or Zinc Oxide and be effective? Simply no, not at all.
At most, you will have an SPF 4 with ZnO and an SPF 8 with TiO2, and a very white final formula!
At The Innovation Company®, we have been active in the mineral filtering business since 1992. In addition, we have a unique analytical laboratory to assist our customers from In Situ observations to In Vitro SPF testing according to ISO 24443:2.
You can therefore discover very simply with us or with your own spectrophotometers the crystal size of your GRASE mineral filters and measure the Critical Wavelength of your samples.
A customer once told me “If the skin is an open wound, then in this case nano filters can penetrate”.
The answer was of course “no”, because the wound has a zeta potential surface charge and protects from bacteria.
And of course, I confirmed that perfectly healthy skin was not a barrier to the organic filters, as these diffused into the capillary blood stream within seconds. Hence the problem with organic filters in the United States.