The first nail strengthener with a famous name came from a woman who kept breaking her nails. Sally Hansen was a real person, and according to Coty, which now owns the brand, she trademarked Hard As Nails in 1957, the first product to carry her name. She later said, as Marie Claire recounts, that she was one of those women who always used to be breaking nails, which is why she wanted something that stopped chipping and cracking.

Formulas have changed a lot since then, and plenty now leave out formaldehyde. OPI, for one, lists Nail Envy as free of formaldehyde and formaldehyde resin among the nine ingredients it leaves out.

A nail strengthener works in one of two ways. Hardeners add a stiff protective coat so nails bend and snap less. Conditioning treatments, oils and keratin serums keep nails flexible so they peel and split less. Most people with weak nails need a bit of both, because a nail that is hard but dry still breaks.

The first grid is strengtheners and hardeners. The second is bond serums, cuticle oils, a hand cream and care polishes. My tip: file in one direction with a fine glass or crystal file and keep nails short while you treat them, because length is what snaps first.

Sally Hansen Advanced Hard As Nails is the descendant of the 1957 original and the most reviewed strengthener in this grid. It hardens nails and softens the look of ridges, with safflower, soybean and linseed oils plus retinol. OPI Nail Envy has biotin, calcium and vitamins A, C and E, goes on in two coats and then one a day, and OPI claims nails are 95 percent stronger in a week. essie Hard to Resist has a purple tint that cancels yellowing and claims less brittle nails after three days.

CND RescueRXx is a daily keratin treatment with jojoba and almond oil for peeling and splitting, and it has the best rating in this grid. Olive & June Nail Strengthener doubles as a primer that extends a manicure by two to three days. Orly Nailtrition is a 14-day treatment with a sheer pink shimmer, made for nails damaged by gel or acrylics. Nail Tek Strengthen Formula 4 is for severely damaged nails, with wheat protein and vitamin B5.

Manucurist Active Smooth is a strengthening ridge filler with a skin-like finish, a nice first coat under color.

What I would skip: wearing a hardener for months without a break. Use it in cycles, the way the Orly and Nail Tek directions suggest, and alternate with oil so nails stay flexible.

Sally Hansen Vitamin E Nail & Cuticle Oil is the most reviewed product in this edit. It is a simple brush-on oil you massage in at night. essie On A Roll Apricot Cuticle Oil comes in a tube with a roller tip, with apricot, jojoba and vitamin E, and it has the best rating in this grid. CND Solar Oil blends almond, jojoba and rice bran oils and keeps natural nails and enhancements tough but flexible. L'Occitane Shea Nail and Cuticle Oil has 30 percent shea oil plus apricot and almond.

OPI Repair Mode is a bond-building serum you apply twice a day for six days, and OPI claims nails get four times stronger. Caudalie Hand and Nail Cream is the antioxidant hand cream to keep by the sink, with a silky finish that sinks in so you can use it after every wash.

For color that also cares, Manucurist Active Glow Blueberry is a treatment polish with a magenta glow tint and glassy shine, and Dior Nail Glow gives an instant French manicure effect with high shine, for when you want nails to look done while you are between strengthening cycles.

What I would skip: cutting your cuticles. Push them back gently after a shower and oil them every night instead, because the cuticle protects the nail as it grows.

I think a nail strengthener works best as part of a small routine. Wear a hardener or strengthening base in cycles, oil the cuticles every night, keep nails short while they recover, and put on hand cream after washing. A fingernail takes months to grow out fully, so give any treatment time before you judge it. Sally Hansen built a brand in 1957 because she kept breaking her nails, and a steady, boring routine is still the fix. Most of the work happens at night, with oil and patience.