FAQ

Hexagonal boron nitride is a multifunctional platy powder: it delivers lubricity, press strength, lustre and thermal conductivity at the same time, which is hard to replicate with a single alternative. The platelet structure gives a low friction coefficient, so it feels silky rather than greasy. The platelets interlock during pressing and provide compact strength. Its refractive index and platy habit produce a soft satin lustre rather than the sparkle of mica. Thermal conductivity adds a slight cooling sensation on skin and helps the bulk dissipate heat. Typical levels: 3-8% in pressed and loose powders, 5-10% in lipstick, 2-5% in liquid foundation. Above about 10% the lustre becomes pronounced, so use it sparingly in matte formulas.

The difference is shape and porosity, and that directly determines oil absorption, skin feel and optical behaviour. Regular silica consists of irregular particles and agglomerates; spherical silica is truly spherical, and porous grades carry interconnected internal channels. The spherical shape gives a ball-bearing effect: particles roll over each other instead of interlocking, so the feel is smoother and spreading is easier. Porosity delivers high oil absorption, mopping up sebum and reducing shine, while the pores scatter light for a soft-focus effect. The trade-off is that porous grades absorb formula oil as well. In low-oil systems, over-dosing can dry out the bulk or even break the emulsion. Keep levels at 2-5%, with somewhat higher levels acceptable in oil-rich formulas.

Bismuth oxychloride was once the workhorse for pearlescent effects, with strong lustre and good coverage, but it carries two unavoidable weaknesses: photostability and regulatory pressure. On photostability, bismuth oxychloride darkens and greys under UV and strong light, so products containing it often show shade drift over shelf life, especially in pale shades. On regulation, the EU lists it as a restricted substance with concentration limits for face and lip use, which adds compliance work for export formulas. The usual replacement is synthetic fluorphlogopite or mica-based pearlescent pigments, which are slightly softer in lustre but far more stable. If the strong bismuth lustre must be kept, restrict it to packaging areas that are not light-exposed and validate photostability thoroughly.

Not on an equal-weight basis. Their functional profiles differ: mica is platy and provides lustre and adhesion, while talc is platy but softer, providing slip and oil absorption with weaker coverage. Replacing talc with mica reduces slip and increases lustre, often making the formula look sparkly. Replacing mica with talc flattens the finish noticeably. If substitution is driven by cost or supply, start at roughly 1:0.7 and fine-tune against measured skin feel and lustre. Also note that talc carries higher regulatory sensitivity because of the asbestos risk. Cosmetic-grade talc must be confirmed asbestos-free, which is one reason many export formulas proactively reduce talc levels.

The core difference is platelet integrity and aspect ratio. Wet delamination cleaves along the platelet planes in a liquid medium, causing little damage and yielding a high aspect ratio. Dry milling relies on mechanical shear, which is efficient but fractures platelets and creates fines and debris. In use, wet-delaminated boron nitride, talc and mica have thinner, more intact platelets, giving clearer lustre, better adhesion and more efficient coverage and soft focus at the same dose. Dry-milled grades scatter light more diffusely and feel rougher. The cost gap comes from yield and process complexity. For premium pressed powders and lipsticks where lustre and adhesion matter, wet-delaminated grades usually deliver better value; for oil-absorbing loose powders, dry-milled material is adequate.

Choose based on the continuous phase: water-in-oil, oil-in-water, or anhydrous. Surface treatment exists to make the powder compatible with that phase. Triethoxycaprylylsilane suits water-in-oil and anhydrous systems; treated powder becomes lipophilic and hydrophobic with good dispersion and a clean feel, which is why it dominates colour cosmetics. Polydimethylsiloxane treatment leans toward slip and water resistance, useful for transfer-resistant formulas. Stearic acid is inexpensive and lipophilic but has limited heat and shear resistance, so it can desorb during high-temperature processing or high-shear dispersion. In practice, check the continuous phase first and the process temperature second. If processing exceeds 80 C, stearic acid treatments are effectively off the table.