Flat definer brush

A flat definer is a liner brush that does not really draw. Its head is a tiny, very dense block of short fibres, cut square across and pinched flat in its ferrule, and it is used by pressing: set against the lash line and pushed or wiggled into the roots, it fills the gaps between the lashes with colour. The result looks like thicker lashes rather than a line, which is why it is also the brush for tightlining, colour pressed into the upper waterline from below.

Its neighbours are both liners. An angled liner is cut on a slant and prints a line with its edge; a fine liner draws with a point. The flat definer’s square edge can draw a crisp line too, turned on its side, but its real work is at the roots, where a pointed or angled brush tends to leave a line floating above the lashes. Rae Morris sells hers on exactly that promise: push the product into the lash line, with no need to drag the brush.

Density and length come first. The denser and shorter the head, the more colour it pushes into the roots and the less it spreads. A very short head, like Hakuhodo’s J521, whose hair its maker gives as 2.3 millimetres long, is sold for extremely thin lines; a firm flat head like MAC’s 212S lays colour along the lash line in a single stroke and doubles as a brow brush. The edge should be straight and firm: press it on the back of your hand, and it should leave a crisp stamp rather than a smear.

Fibre follows the formula. Synthetic fibre suits gel and cream liner, and anything used near the waterline, because it does not absorb product and washes clean; most flat definers are synthetic, several sold as vegan. Hair grips powder and presses it softly: Hakuhodo makes its J521 of horse hair. A slightly longer, more flexible head spreads colour a little as it presses, which suits a softer look; a very short, stiff one leaves the crispest edge and is the better tightliner.

For tightlining, choose a head no wider than the gap you are filling, since a brush that is too wide lands on the lid as well. Anastasia Beverly Hills sizes its A1 for the job, with thinly packed fibres, and Trish McEvoy gives its Brush 11 a razor-thin edge to reach the base of the lashes.

For definition along the upper lashes, dip the flat edge into gel or a dark powder shadow, tap off the excess, and press it into the lash roots from above, working from the outer corner inward in small wiggles rather than strokes. Build intensity with a second press where the lashes are sparse. Used dry with powder, the brush gives a soft line; dampened first, a sharper one.

To tightline, tilt your head back slightly, look down into a hand mirror and lift the upper lid gently at the outer corner. Press the loaded edge upward into the waterline beneath the lashes in short touches; there is no need to cover the whole rim. Use a product its maker says is suitable for the waterline, and stop if your eyes water or sting.

Below the eye, use less. Press only the outer half of the lower lash line, in a softer colour than above, because a dark line pressed right round the eye closes it up. For a gentler finish anywhere, press a matte shadow a shade lighter than the liner over the pressed line: it softens the edge without losing the definition at the roots.

Hygiene matters more with this brush than with any other, because it touches the rim of the eye. Wash it after each use with gel or cream, never share it, and replace it when the edge will no longer hold its shape.

The oldest tool for colour at the roots of the lashes is not a brush but a rod. The Metropolitan Museum of Art holds a kohl tube of faience and gold from Egypt’s Eighteenth Dynasty, about 1550–1300 BCE, catalogued with its applicator, a hematite stick 4.5 centimetres long.^[1] Edward Lane, writing about the Egypt of 1833–35, found the same kind of tool in common use: kohl “applied with a small probe, of wood, ivory, or silver, tapering towards the end, but blunt”, moistened, dipped in the powder “and drawn along the edges of the eyelids”. The probe, he noted, “is called ‘mirwed’”.^[2]

The historian James Bennett describes how such a rod works on the waterline: passed through the base of the lashes with the eyes closed, it leaves powder on the wet inner rim of the lid, “creating a smooth, even line”. The French house Dorin gave its customers the same instruction for El Mesdjem, a kohl it sold in the late nineteenth century: lay the coated wand between the lids, close the eye on it and slide it out.^[3]

The flat definer does that work from outside the eye, with a shape borrowed from the painter’s box: square-ended and short-bristled, what the Getty’s art vocabulary calls a bright.^[4] It presses colour into the same roots that the rod once coated from within.