What silicone elastomers are
Silicone elastomers are crosslinked polydimethylsiloxane networks — three-dimensional polymer structures formed when linear PDMS chains are chemically linked at multiple points rather than remaining as free-flowing chains. The degree of crosslinking and the length of the chains between crosslink points determine the mechanical properties of the network: highly crosslinked systems form rigid gels, while lightly crosslinked systems form soft, deformable solids.
In cosmetic applications, silicone elastomers are used in two primary forms: as gels (the elastomer network swollen with a carrier fluid, typically a cyclic or linear silicone) or as powders (dried and milled elastomer particles). Both forms deliver similar functional properties — soft-focus optical effects, cushion and slip on application, and dry-down to a non-greasy finish — but they are incorporated differently and interact differently with emulsion systems.
The optical science of soft-focus
The soft-focus effect — the slight blurring and diffusion of light that makes skin appear smoother in person and in photographs — is a physical phenomenon caused by how elastomer particles or gel droplets scatter incident light. Spherical elastomer particles in the 1–10 micron size range scatter light in multiple directions simultaneously (Mie scattering), which reduces the specular (mirror-like) reflection from skin surface features like fine lines and pores and increases diffuse reflection.
The refractive index of the elastomer also plays a role: when the refractive index of the elastomer particle is close to that of skin (approximately 1.45), the scattering at the particle–skin interface is less pronounced, and the visual effect is a natural-looking softening rather than a powdery or whitened finish. This is why formulation scientists specify elastomers carefully for different complexion types and skin tones — the optical performance varies with loading level and particle size distribution.
Sensory mechanics: cushion, slip, dry-down
Beyond optics, silicone elastomers define the tactile experience of premium foundation formulations. On contact with skin, the gel phase provides immediate cushion — a slight resistance that consumers describe as bouncy or cloud-like — distinct from the immediate spread of conventional silicone fluids. During the spread phase, the elastomer particles or gel droplets remain dispersed in the carrier, delivering continuous lubrication as the formula is worked across the skin surface.
As the volatile carrier evaporates (or as the water phase is absorbed by skin in an emulsion foundation), the elastomer remains deposited on the surface, contributing to the dry finish. In well-formulated foundations, this transition from wet application through spread to dry-down happens smoothly without draggy or patchy behaviour — a sign that the elastomer loading is appropriate for the silicone phase composition and that the emulsification system is stable.
NISH EL450 and EL455: two grades, two applications
NISH EL450 is a carrier-swollen silicone elastomer gel — the crosslinked polymer network pre-swollen in a silicone carrier fluid. It is used directly as a formulation ingredient and is particularly suited to anhydrous systems (oil-based foundations, lip products, and stick formats) where the carrier fluid forms part of the continuous phase. Typical use levels in foundation are 5–15% for full soft-focus effect; lower levels (2–5%) contribute cushion and slip without significant optical modification.
NISH EL455 is a silicone elastomer powder — the dried and milled form of a similar crosslinked network. Powders are preferred in water-continuous emulsions and in formulations where precise particle distribution is required for opacity or tone control. The powder form can be dry-blended with pigments before dispersion, and it generally contributes less to formula viscosity compared to the gel grade at equivalent loading.
Foundation formulation example
A typical full-coverage foundation using NISHKA elastomers might include: NISH EL450 (elastomer gel) at 8%, providing the primary soft-focus and cushion character; NISH PT103 (propyl trisiloxane) at 10% as the volatile carrier; NISH DML100 (dimethicone 100 cSt) at 5% for spreadability; silicone emulsifier at 3–5% for the oil-in-water continuous phase; and pigments at 10–25% depending on coverage target. At this construction, the foundation delivers smooth application, a soft-matte dry-down, and 8–10 hours wear.
Synergies with other silicones
Silicone elastomers work best in a balanced system. NISH PT103 or a cyclopentasiloxane variant provides the initial fluidity needed for elastomer gel incorporation and spread. NISH DML100 (dimethicone 100 cSt) extends the spread phase and prevents the elastomer from drying down too rapidly in application. Phenyl silicones (NISH PTM 4710) can be added to enhance the gloss phase or modify the refractive index profile if a dewy rather than matte finish is targeted.
Common formulation mistakes to avoid
Overloading: adding too much elastomer gel (above 15–18%) usually increases formula viscosity beyond pump-dispensable range without proportional improvement in soft-focus performance — more elastomer does not deliver more blur. High-shear dispersion: silicone elastomer gels should be incorporated under moderate shear only; high-shear homogenisation can break down the crosslinked network and permanently reduce its functional properties. Incompatible emulsifiers: conventional non-ionic emulsifiers designed for mineral oil systems may not provide the interfacial stability required when the oil phase is predominantly silicone — use a silicone-compatible emulsifier (polyglyceryl or PEG-12 dimethicone types) for reliable emulsion stability.
