SUN CARE
67
Reducing opacity, UV filters in mineral sunscreen
Jamie Eldridge, Daphne Benderly – Presperse
Formulating higher SPF formulations without the increased use of UV filters is desirable, particularly with mineral sunscreens. Higher UV filter load can lead to increased opacity on the skin which is unfavourable. If higher SPF values can be achieved with
less mineral filters, decreasing the opacity on the skin, the formulator will then be able to create a more desirable product for the consumer. Higher SPF formulas are becoming
increasingly popular with consumers. Consumers are also favouring natural ingredients over synthetics, leading to an increase in demand for mineral based sunscreen formulations. This can pose challenges to the formulator
by way of unpleasant whitening aesthetics and trouble achieving the desired SPF. The addition of a sunscreen booster (considered as a material that on its own does not yield an SPF value >2 in an emulsion but when combined with UV filters can show a synergistic effect) helps the formulator mitigate these challenges. This article covers a comprehensive SPF boosting study that was conducted on a mineral sunscreen base containing both titanium dioxide and zinc oxide, exploring the effects of booster use level and formulation processing procedures. This proof of concept study was expanded with a study in a base containing only zinc oxide as a UV filter.
Booster INCI Silica (1)
These studies included also the
measurement of sunscreen opacity, to supplement the measurement of in vitro SPF, to meet the consumer demand for sunscreen performance. In the zinc oxide system, we were able to achieve a high SPF with the use of an SPF booster, while reducing the UV filter loading and thus reducing opacity.
TABLE 1: POWDERS EVALUATED IN SPF BOOSTING STUDIES Booster Tradename Chiffon P3-R
Luxsil AL Free
Silica Balloon BA4 Spheron 20MB
Spheron P1500-030 Spheron LP-230 Spheron P-4000
Serisense SM9 Serisense SM13
Serisense SM15 OSSfEC Botanilica BA4
Calcium Sodium Borosilicate Silica (2) Silica (3)
Silica (and) Methicone Silica (4) Silica (5)
Microcrystalline Cellulose (1) Microcrystalline Cellulose (2)
Microcrystalline Cellulose (and) Cellulose Gum
Oryza Sativa (Rice) Starch (and) Oryza Sativa (Rice) Bran Wax
Silica (6)
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Oil Absorption 20 mL/100g
40 mL/100g 40 mL/100g 60 mL/100g 60mL/100g 230mL/100g 60 g/100g
110 g/100 g 100 g/100 g
55 g/100 g
65mL/100g 50mL/100g
Average Particle Size (mM)
5.0 11.0 3.5 6.0 9.5
13.9 25.7
9.0
13.0 15.0
9.0 4.0
Natural
Origin Index 1 1 1 1
0.98 1 1
1 1
0.993
1 1
Experimental details Boosting powders Twelve powders were selected for testing boosting efficacy in the proof of concept study (mixed mineral sunscreen base formulation). The powders evaluated are shown in Table 1, along with powder oil absorption, particle size and Natural Origin Index according to ISO 16128. Of these powders, there are six with INCI
Silica, the silicas differ in oil absorption and average particle size, and also in qualitative parameters such as feel and spreadability. Two of the powders are hydrophobically modified, again to give formulators options when choosing a boosting powder. All the powders have a high Natural Origin
Index (according to ISO 16128), in alignment with current consumer trends.
In vitro SPF testing In vitro SPF measurements were taken using a LabSphere UV-3000 on moulded PMMA plates in compliance with the FDA and Colipa standards.1
Film thickness on each plate was
2mg/cm2 per plate. Three test samples were plated per formulation and nine locations per plate were measured. The average was then taken for all measurements to determine product SPF.
March 2025 PERSONAL CARE
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