Base coats for nails not only prevent the damage some varnishes cause - they also create a smooth canvas on which to apply the polish. We've tested four so you don't have to.
Kose's Esprique hardener and base coat (HK$70 for 8ml) is very rich but dries quickly to leave a thin, smooth surface. It's described as being "nude" in tone, but is more or less transparent. The base contains sweet almond oil to nourish weak or brittle nails.
Kanebo's Lunasol Base Coat N (HK$140 for 10ml) is an enhanced version of the Japanese brand's first base coat and includes a blue pigment which gives a glossy, subtle, pearl-like finish. When two layers are applied, it can be used on its own. It's also designed to strengthen nails.
O.P.I's Natural Nail Base Coat (HK$68 for 15ml) has been around for ages. It's known to create a strong foundation for varnish, protect nails from staining and make polish last longer. The only downsides are that it can make removing varnish difficult and your nails don't look particularly healthy afterwards.
Spa Ritual's Truebond Strong Hold Basecoat (HK$185 for 15ml), suitable for vegans, is said to be "formulated with advanced polymer technology", whatever that means, to bind polish to nails for longer. Nails are matte after use, but they don't feel all that smooth. The base is free of chemicals such as toluene and formaldehyde and doesn't have the sharp smell the others have - although its own fragrance isn't exactly pleasant.