Illuminating primer

An illuminating primer is a primer that carries pearl. Its light comes from pearlescent pigments, thin flakes of mica, natural or synthetic, coated with titanium dioxide and sometimes with iron oxides, suspended in a light lotion, gel or fluid. Worn under foundation, the flakes send a little light back through the layer on top, so the skin reads as luminous rather than shimmering; the finer the flake, the softer the effect. Some are tinted as well, pink, champagne, gold or bronze. The base around the pearl is often hydrating, which is one reason illuminating primers suit dry skin better than oily.

Its neighbours are close. A highlighter goes on top of foundation, on the high points of the face, and is meant to be seen; an illuminating primer goes underneath, or into the foundation, and is meant to be sensed rather than noticed. A hydrating primer can look dewy, but its glow is moisture, not pearl. And the liquid glow drops and complexion boosters sold for mixing into foundation are the same idea, often in the same kind of bottle; what makes a product a primer here is that its maker sells it for wearing under make-up.

The pearl has a colour, and that is the first thing to match. Pink and cool champagne tones flatter fair and cool skin; gold, peach and warm champagne suit medium and olive skin; bronze and deep gold keep deep skin from looking grey or ashy, which a pale pearl can do. Several illuminating primers come in two or three tones for exactly that reason. Look at a swatch on the jaw in daylight: the right one warms the skin without looking like a separate layer.

The second choice is size. A fine, satin sheen reads as healthy skin, even close up; a larger pearl or a visible shimmer reads as make-up, and it catches on every pore and line. If your skin is textured, or oily enough to shine on its own, choose the finest you can find and keep it off the T-zone.

Worn all over under foundation, an illuminating primer gives a soft, even radiance. Smooth it on thinly with the fingertips and let it set for a minute before the base goes on. Patted only onto the high points, the tops of the cheekbones, the brow bone and the centre of the forehead and chin, it puts light where light would naturally fall and leaves the rest of the face as it was. Mixed a drop at a time into foundation, it sheers the foundation and lifts its finish, which is the simplest way to make a matte formula look fresher.

On a bare day it can be worn alone, over moisturiser and under a touch of concealer. However you use it, set with powder only where you need to. A full face of powder over an illuminating primer puts out the light it was worn for.

The foundation on top decides how much of the light comes through. Under a sheer foundation or a skin tint, an illuminating primer shows plainly, and a little goes a long way. Under a medium-coverage formula it gives a soft sheen through the base; under a full-coverage or heavily matte one much of it is hidden, which is why people who wear more coverage usually get more from patting the primer onto the high points than from wearing it all over. A matte foundation over an illuminating primer suits skin that is oily in the centre and dry at the edges: matte where it counts, with light underneath elsewhere.

A dewy foundation over an illuminating primer is the brightest combination of all, and on oily skin it can tip into shine within hours. If it does, keep the primer to the cheekbones, and use a mattifying primer or a light powder through the T-zone. Under a foundation with shimmer of its own, one source of light is usually enough.

A pearly base is older than the illuminating primer. The best vanishing creams, the creams women smoothed on under their powder in the early twentieth century, were valued for a pearly, satin-like sheen, which chemists associated with quality and worked to reproduce. In 1924 the chemist W. A. Poucher explained how adding oleic acid changed the effect: “One per cent yields a pearliness. Two per cent gives a satiny appearance.”^[1] The sheen was eventually traced to platelet-shaped crystals formed as the cream was made, which reflected and refracted the light.^[1]

Pearl pigment reached skin creams after the Second World War. A fashion for pearl lustre followed the pastel make-up of the post-war years, and artificial pearl, until then used only in nail polish, went into make-up, skin creams and hair products. How much a product needed depended on what else was in it: lipsticks, full of opaque colour, needed more, and transparent creams, which wanted only a subtle lustre, less.^[2] The primers below belong to the second family, clear or faintly tinted bases that carry only as much pearl as a subtle lustre needs.

An illuminating primer puts that pearl where the vanishing cream once was, under the rest of the make-up, so that its light arrives softened by the layer on top. That is the whole difference between it and a highlighter: not what it is made of, but where it is worn.