If possible, put on rubber gloves to protect hands from the negative effects of chemicals and water. For example, if you're processing furniture stain, use special gloves, designed for that purpose. If no suitable gloves can be found, use a good cream for hands and nails before beginning to work. It will help you prevent the nails' stratifying, becoming brittle and fragile.You may have already noticed that the cracks and brittleness are formed on the same partes of the nail, while some nails more frequently "suffer" than the other. I have, for example, usually defects on the right side of big finger nails. If you find such sites at your nails, pay special attention during a manicure, eliminating the slightest texture and covering the vulnerable places a protective wax layer of ointment. For even better protection, use a small amount of vaseline or other nutritious ointment to cover the bottom of the toe nails. This is especially important if your nails were outside edge of the fingers. The nails' tips is the oldest one, dry areas, wich trend to break and stratify, so they require additional protection.