Some cooks prefer to use a candy thermometer and some prefer to use the old-fashioned cold-water way to test the doneness of candy. Below there are directions for both.
Thread Stage - begins at 230 degrees F. - Makes a long thread when dropped in cold water.
Soft Ball - 234 degrees F. - Forms a soft ball that doesn't hold its shape. Cream candies, fudge, fondants are done at the softball stage.
Firm Ball - 246 degrees F. - This ball will only flatten with pressure. Divinity and Caramels.
Hard Ball - 250 degrees F. - This ball will hold its shape when pressed. Taffy.
Soft Crack - 270 degrees F. - Separates into bendable threads. Toffee and Butterscotch.
Hard Crack - 300 degrees F. - Becomes brittle. Peanut Brittle.
Caramelize - 310 degrees F.