Cosmetic Ingredients · Functional Additives · Rheology Control

Fumed Silica for Cosmetics & Personal Care

SEMISIL grades deliver precision rheology control, silky texture, anti-caking performance, and SPF stabilization across leave-on and rinse-off formulations. Hydrophilic and hydrophobic surface chemistries available, fully EU INCI compliant.

Silicon Dioxide (INCI) Rheology Modifier Anti-Caking Agent SPF Enhancement EU 1223/2009 Compliant Hydrophilic & Hydrophobic

Overview Functional Benefits Product Portfolio Formulation Guide FAQ

Overview: Why Fumed Silica in Personal Care

Fumed silica (pyrogenic silica) is manufactured by high-temperature flame hydrolysis of chlorosilanes, producing a three-dimensionally branched network of primary particles in the 5–30 nm range. The resulting material has an extraordinarily high specific surface area (100–400 m²/g), negligible particle density, and a surface chemistry that can be tuned from strongly hydrophilic to fully hydrophobic — making it uniquely suited to the demands of cosmetic formulation.

In personal care, fumed silica functions at very low use levels (0.2–3.0 wt%) as a thixotropic gelling agent in aqueous and anhydrous systems, as a dry-feel and silky-slip additive in pressed powders and skin-care creams, and as a UV-scatterer stabilizer in mineral sunscreens. Its amorphous (non-crystalline) structure is approved under EU Cosmetics Regulation 1223/2009 Annex III and listed in the INCI Dictionary as Silicon Dioxide; hydrophobic surface-treated variants carrying a PDMS or DDS modification are additionally listed under CI 77811.

INCI Identifiers: Hydrophilic fumed silica → Silicon Dioxide (CAS 7631-86-9). Hydrophobic PDMS-treated → Silica Dimethyl Silylate / CI 77811. Hydrophobic DDS-treated → Silica Dimethyl Silylate / CI 77811. All three SEMISIL grades are compliant with EU Regulation 1223/2009 and ISO 22716 GMP guidelines.

Unlike synthetic polymers and natural gums, fumed silica is chemically inert, free of preservatives, and stable across the pH range 4–10, making it compatible with acidic AHA serums, neutral moisturizers, and alkaline depilatory creams alike. It does not support microbial growth and does not contribute odor, color, or taste to a formulation — essential attributes for transparent gels, colorless serums, and flavored lip products.

Surface Area Range

100–380 m²/g depending on grade, enabling high adsorption capacity and structure-forming efficiency at 0.5–2.0% loading.

Primary Particle Size

7–16 nm amorphous silica particles — below the threshold for visible light scattering, yielding transparent to translucent gels.

pH Stability

Functional across pH 4–10; no viscosity collapse in acidic vitamin C serums or alkaline soap bases. Silanol groups remain intact.

Functional Benefits in Cosmetic Formulations

Rheology Modification in Emulsions and Gels

Fumed silica builds a reversible hydrogen-bond network between surface silanol groups, creating a thixotropic, shear-thinning rheology profile ideal for pump dispensers and squeeze tubes. At rest, a 1.5% SEMISIL 200 dispersion in a water-in-oil emulsion delivers gel-like firmness (static yield stress > 15 Pa) that collapses instantly under applicator shear and recovers within 30–120 seconds — preventing product run-off on skin while maintaining a smooth, non-tacky after-feel.

In anhydrous formulations such as facial oils, cleansing balms, and stick deodorants, hydrophobic grades (SEMISIL R202, R272) provide equivalent thickening without the water sensitivity of fumed silica silanol networks, and without the crystalline wax drag associated with C20–C40 waxes.

Anti-Caking and Flow Control in Pressed Powders

Compressed eyeshadow, face powder, and body shimmer suffer from ingredient separation, clumping during humid storage, and poor pigment-binder cohesion. At 0.3–1.0 wt%, fumed silica adsorbs free fatty acids and moisture released from binder waxes, maintains discrete pigment and filler particle separation, and provides the micro-roughness needed for porous press binder adherence. The silica network also acts as a lubricant slip plane, contributing to the characteristic smooth “cushion” texture valued in prestige powder formulations.

Silky Texture and Dry-Slip in Skin Care

Surface-treated hydrophobic grades reduce the wet, greasy drag of silicone and ester emollients in day creams, primers, and BB creams. At 0.5–1.5%, SEMISIL R202 disperses into the oil phase as a dry, fluffy powder, forming a structural network that absorbs excess sebum and emollient while leaving a powdery, velvet tactile — without the white cast associated with talc or mica at equivalent loading.

SPF Stabilization and UV Scatterer Dispersion

Titanium dioxide and zinc oxide used as mineral UV filters are notoriously prone to flocculation and sedimentation in sunscreen emulsions. Fumed silica at 0.5–2.0% acts as a physical spacer and dispersant aid, reducing agglomerate size of TiO₂/ZnO particles, improving rheological suspension stability, and raising SPF reproducibility between production batches. Hydrophobic SEMISIL R272 is especially effective in anhydrous SPF sticks and oil-based tinted sunscreens.

Transparency in Aqueous Gels and Serums

Because primary particle diameter (7–16 nm) is far below the wavelength of visible light, properly dispersed SEMISIL 200 in a carbomer or hyaluronic acid serum contributes negligible haziness. This allows formulators to achieve thixotropic, film-forming gel structure without compromising the clear, premium visual cue expected in serum packaging.

Adsorption of Active Ingredients

High surface area enables loading of skin-active compounds (retinol, niacinamide, peptides) onto silica surfaces, facilitating controlled-release behavior and improving oxidative stability of light-sensitive actives.

Stabilization of W/O Emulsions

Hydrophobic grades partition to the water–oil interface, acting as Pickering stabilizers that resist coalescence without additional emulsifier, enabling formulation of natural/COSMOS-certified emulsions with minimal surfactant.

Lip Product Structure

In wax-free liquid lipsticks and glosses, fumed silica provides body and suspension stability for mica pearls and pigments, preventing separation on storage without hard wax syneresis at elevated temperature.

Deodorant & Antiperspirant Boosting

At 0.5–1.0%, fumed silica improves stick hardness uniformity and adsorbs malodor volatiles, reducing fragrance load requirements and improving long-wear odor control without compromising skin-feel.

Product Portfolio: SEMISIL Cosmetic Grades

Three SEMISIL grades cover the full range of cosmetic application needs — hydrophilic for aqueous systems, PDMS-treated hydrophobic for silicone-compatible systems, and DDS-treated hydrophobic for mineral oil and ester systems. All grades are manufactured under ISO 9001 quality management and batch-certified against EU Cosmetics Regulation 1223/2009 ingredient purity requirements.

Grade	Surface Treatment	INCI Name	BET Surface Area	Avg. Primary Particle	Moisture Content	Primary Cosmetic Uses
SEMISIL 200	None (hydrophilic)	Silicon Dioxide	200 ± 25 m²/g	12 nm	≤ 1.5% (2h, 105°C)	Aqueous gel thickening, transparent serum structure, W/O emulsion stabilization, anti-caking in talc-free powder
SEMISIL R202	Polydimethylsiloxane (PDMS)	Silica Dimethyl Silylate / CI 77811	100 ± 20 m²/g	12 nm	≤ 0.5% (2h, 105°C)	Silicone-phase thickening, primer & foundation dry-feel, SPF suspension, Pickering emulsifier, anhydrous stick structure
SEMISIL R272	Dichlorodimethylsilane (DDS)	Silica Dimethyl Silylate / CI 77811	110 ± 20 m²/g	16 nm	≤ 0.3% (2h, 105°C)	Mineral oil / ester thickening, anhydrous sunscreen sticks, wax-free lipstick structure, natural/COSMOS formulations, powder compaction

Packaging & Handling: All SEMISIL cosmetic grades are supplied in multi-wall kraft paper bags with polyethylene inner liner (10 kg, 20 kg) or bulk supersacks (300 kg). Material Safety Data Sheets, Certificate of Analysis, and EU REACH/SCCS dossier extracts are available upon NDA execution. Samples (100 g) available for qualified formulators — see CTA below.

Surface Chemistry Detail

SEMISIL 200 carries a fully hydroxylated surface with silanol density of approximately 2.5 –OH/nm². It disperses spontaneously in water and polar solvents, requiring only moderate shear (rotor-stator, 1500–3000 rpm, 5–10 min) to achieve primary aggregate breakdown. Thickening efficiency is maximized by pre-dispersion in a low-viscosity aqueous phase before addition of electrolytes or polyols, which compete for hydrogen-bond sites.

SEMISIL R202 replaces surface silanols with trimethylsiloxy groups via PDMS treatment, yielding a water-contact angle > 100°. It disperses in silicone oils (dimethicone, cyclopentasiloxane), fatty alcohols, esters, and mineral oils but is incompatible with neat water phases. Mixtures of cyclomethicone and SEMISIL R202 (1:5 ratio) can be pre-processed into a paste master batch for ease of incorporation into emulsion bases.

SEMISIL R272 uses dichlorodimethylsilane to achieve the highest degree of surface hydrophobicity (water-contact angle > 120°), making it preferred for systems where any residual hydrophilicity would cause moisture uptake — anhydrous SPF sticks, solid perfume, and compressed powder compacts intended for humid-climate markets.

Formulation Guide

Fumed silica is a low-density, high-surface-area powder that requires specific handling and incorporation protocols to achieve full performance. Improper addition sequence or insufficient dispersion is the primary cause of visible aggregates, grainy texture, and suboptimal viscosity build in finished formulations.

Dispersion Protocol: Aqueous Systems (SEMISIL 200)

Pre-blend SEMISIL 200 with a small portion (2–5×) of a low-viscosity aqueous phase (deionized water, glycerin dilution, or propanediol) at room temperature under high-shear (rotor-stator at 3000 rpm, 5–8 min) to form a 5–15% pre-dispersion.
Slowly add the pre-dispersion to the main aqueous phase under moderate agitation (anchor stirrer, 200–400 rpm). Avoid direct powder addition to hot water — thermal convection disrupts aggregate breakdown.
If electrolytes (NaCl, magnesium sulfate) are required, add after SEMISIL 200 is fully dispersed. Electrolytes screen silanol surface charges and reduce thickening efficiency by 15–30% at concentrations above 0.5 M.
Allow 30 min rest before viscosity measurement — the hydrogen-bond network requires equilibration time after shear history.

Dispersion Protocol: Anhydrous / Oil-Phase Systems (SEMISIL R202, R272)

Melt wax components and heat oil phase to 70–75°C. Add SEMISIL grade at temperature before wax solidification begins — elevated temperature reduces oil viscosity, improving aggregate wetting.
High-shear mixing (rotor-stator, 2000–4000 rpm) for 5–10 minutes followed by a 3-roll mill pass at 30–50 µm gap closure is recommended for pressed powder applications requiring maximum aggregate disruption and pigment–silica co-dispersion.
For silicone-continuous systems (SEMISIL R202), pre-wet with a small quantity of low-viscosity dimethicone (2 cSt) before adding heavier silicone fractions — silica wets out faster in low-viscosity medium.

Recommended Use Levels by Application

Application	Recommended Grade	Use Level (wt%)	Primary Function	Key Processing Note
Aqueous face serum	SEMISIL 200	0.3–0.8%	Thixotropic gel structure, transparency	Pre-disperse in water; add before carbomer neutralization
O/W moisturizing lotion	SEMISIL 200	0.5–1.5%	Viscosity stabilization, anti-syneresis	Add to water phase; allow equilibration before emulsification
W/O rich cream	SEMISIL R202	0.8–2.0%	Oil-phase thickening, Pickering stabilization	Disperse in oil phase at 70°C with high shear before emulsification
Silicone-based primer	SEMISIL R202	1.0–2.5%	Dry-feel, pore-blurring, sebum adsorption	Pre-slurry in cyclomethicone (1:5); add to main batch cold
Pressed powder / eyeshadow	SEMISIL R272	0.3–1.0%	Anti-caking, flow, soft-focus texture	Dry-blend with pigments before binder/oil addition; 3-roll mill recommended
Mineral sunscreen SPF30+	SEMISIL R272	0.5–2.0%	TiO₂/ZnO dispersion aid, suspension stability	Add to oil phase; pre-mill with UV filters before emulsification
Anhydrous lipstick / lip balm	SEMISIL R272	0.5–1.5%	Wax structure, pigment suspension, heat stability	Add at melt; apply high shear before casting; avoid re-melt cycles
Stick deodorant / antiperspirant	SEMISIL R202	0.5–1.2%	Hardness modulation, odor adsorption	Add to wax phase during melt; stir continuously until casting temperature

Inhalation Precaution: Fumed silica is an amorphous powder with bulk density as low as 40–60 g/L. Dry weighing and transfer operations must be conducted with local exhaust ventilation and appropriate respiratory protection (minimum FFP2 mask). Once incorporated into the formulation (dispersion, paste, or finished product), no inhalation risk applies. Refer to product SDS Section 8 for full occupational exposure guidance per OSHA PEL / EU OEL.

Compatibility Notes

SEMISIL 200 thickening efficiency is reduced by cationic polymers (polyquaternium series, BTMS) at concentrations above 0.3%, by high concentrations of ethanol (> 20%), and by chelating agents such as EDTA at elevated pH. In such systems, consider SEMISIL R272 in the oil phase or use a co-gelling polymer combination. High-pressure homogenization above 500 bar irreversibly destroys the silica aggregate network and should be avoided after silica addition.

Frequently Asked Questions

Is fumed silica safe for use in leave-on cosmetics such as facial moisturizers and sunscreens?

Yes. Amorphous fumed silica (Silicon Dioxide, CAS 7631-86-9) has been evaluated by the Scientific Committee on Consumer Safety (SCCS) and the CIR Expert Panel and found safe for use in cosmetic leave-on and rinse-off products within established concentration limits. It is approved under EU Cosmetics Regulation 1223/2009 and is on the positive list for colorants as CI 77811 in its surface-treated form. Importantly, fumed silica is amorphous — it does not contain crystalline silica (quartz, cristobalite) and therefore does not carry the respiratory hazard classification of crystalline silica under GHS/CLP. Finished cosmetic formulations present no inhalation risk.

What is the difference between SEMISIL R202 (PDMS-treated) and SEMISIL R272 (DDS-treated), and how do I choose between them?

Both grades are hydrophobic fumed silica but differ in surface chemistry and resulting polarity/compatibility profile. SEMISIL R202 is treated with polydimethylsiloxane (PDMS), which leaves a relatively longer, more flexible silicone chain on the surface — this makes it particularly compatible with silicone oils (dimethicone, cyclopentasiloxane, phenyl trimethicone) and gives a softer, more cushion-like feel in silicone-heavy formulations such as primers and light emulsions. SEMISIL R272 uses dichlorodimethylsilane (DDS), producing a denser methyl-silyl surface with higher hydrophobicity (water contact angle > 120°) and better compatibility with mineral oils, synthetic esters, and natural lipids. R272 is the preferred choice for anhydrous sticks, natural/COSMOS-certified formulations where silicone oils are excluded, and pressed powder applications where maximum moisture barrier during compaction is required.

At what use level does fumed silica become visible as white specks or produce unwanted opacity in a clear gel formula?

Properly dispersed fumed silica does not produce visible white specks — specks indicate undispersed aggregates, which are a process failure rather than an inherent property. SEMISIL 200, when dispersed with adequate rotor-stator shear in a clear aqueous gel, imparts a slight blue-tinted opalescence (Tyndall effect) at concentrations above approximately 1.5% but remains substantially transparent at 0.3–0.8%, which is the typical range for serum and gel applications. The primary particle diameter of 12 nm (SEMISIL 200) is well below the 400 nm wavelength threshold for strong visible-light scattering — transparency is maintained as long as aggregates are broken down to below 200 nm hydrodynamic diameter. To verify dispersion quality, dynamic light scattering (DLS) of a diluted sample should show a primary peak below 150 nm. If larger particles are detected, extend rotor-stator dispersion time or reduce glycerin concentration in the pre-dispersion phase, as polyols above 40% can slow aggregate wetting.

Can SEMISIL grades be used in COSMOS/ECOCERT-certified natural cosmetics?

Silicon Dioxide produced by flame hydrolysis (fumed silica) is listed on the COSMOS-approved substance list as a mineral ingredient of non-biological origin, permitted without restriction in all COSMOS product categories (leave-on, rinse-off, oral care). For hydrophobic grades (SEMISIL R202, R272), the surface treatment agent must also be permitted under the applicable certification body rules. Under COSMOS v3.0, silicone-based treatments (PDMS) are not included in the approved ingredient list, so SEMISIL R202 may not qualify for COSMOS certification. SEMISIL R272, treated with dichlorodimethylsilane which leaves a methyl-silyl (non-polymeric silicone) surface, falls into a regulatory interpretation zone — formulators should seek confirmation from their certification body prior to use. For fully COSMOS-certified anhydrous formulations, SEMISIL 200 dispersed in approved oils remains the safest choice for hydrophobic-effect approximation.

How does fumed silica compare to synthetic hectorite (Laponite) and carbomer as a cosmetic thickener?

These three thickeners operate by distinct mechanisms and occupy complementary formulation spaces. Carbomer (carbopol) provides high-efficiency thickening at 0.1–0.5% in aqueous systems but requires pH neutralization to pH 6–7 and loses viscosity sharply below pH 4.5 — precluding use in low-pH AHA/vitamin C formulations. Synthetic hectorite (Laponite) forms house-of-cards clay platelets in water, yielding firm, structured gels with excellent suspension properties for pigments and particles, but is sensitive to electrolytes above 0.1 M and has limited oil-phase utility. Fumed silica (SEMISIL 200) functions across pH 2–10, tolerates moderate electrolyte concentrations, and is the only option available in both hydrophilic and hydrophobic variants — making it uniquely applicable to oil phases and anhydrous sticks. In practice, fumed silica is frequently used in combination with carbomer or hectorite in hybrid systems: the silica provides initial structure and thixotropy while the polymer imparts long-term stability and cling. Typical hybrid ratio: SEMISIL 200 at 0.4% + carbomer at 0.2% delivers viscosity profiles that neither material achieves alone.