How to test, wear and keep a perfume

Testing. Paper tells you the first ten minutes; skin tells you the truth. Spray one wrist, do not rub it against the other (rubbing crushes the top notes and heats the skin, so you smell the base too early), and go about your day. Judge at ten minutes, at an hour and at four hours: that is the top, the heart and the base, and you live with the base.

Where. Pulse points: wrists, neck, behind the ears, the inside of the elbows. Warm skin lifts the scent. For a longer trail, a spray on the hair or the collar; fabric holds perfume longer than skin but can stain silk, so test first.

How much. At 40 percent, two sprays for a strong scent, three for a light one. More is not stronger, only louder.

When it fades faster. Dry skin, hot weather and freshly washed skin all shorten a scent. Moisturise first; the oil holds the perfume. In summer, a spray on clothing before you leave the house does more than a third spray on skin.

Keeping it. Heat and light are the enemies. A bathroom shelf, a car, a windowsill: all will turn a perfume in months. Keep bottles in a drawer or a cupboard, cap on, and a bottle will last two years and more. The fridge is not necessary and not harmful.

Why it smells different on your friend. Skin chemistry, diet, skin temperature and how dry the skin is all change the balance of notes. A scent that turns sweet on one person turns woody on another. This is also why layering works differently for everyone.