Measure Water Carefully

• The first stage in making praline is boiling sugar and water to create the syrup that will harden into candy. When you cook the mixture, the water evaporates -- the less water that remains, the harder the praline will be. If you've added just a little too much water, your praline may not harden. Use a glass cup designed for liquids, and measure accurately by setting the cup on a flat surface and bending down to ensure that the water is exactly on the intended line.

Use a Candy Thermometer

• You could use the cold-water test to ensure that your praline reaches the hard-crack, brittle stage by dropping a spoonful of the syrup into cold water, where it should separate into hard, breakable threads. But a candy thermometer that registers 100 to 400 degrees Fahrenheit gives you a more precise reading and ensures that the praline will harden. For hard praline, cook the syrup to between 300 and 310 F.

Refrigerate to Defeat Humidity

• Humidity affects whether praline hardens completely because the moisture in the air gets into the candy mixture, keeping it soft. It may seem counterintuitive, but the air in your refrigerator is low in humidity -- fruit and vegetable drawers are the exception, because produce needs a higher level of moisture to stay fresh. Once your praline has finished cooking, place it in the refrigerator to harden.

Go Easy With Stirring

• Once the praline comes to a boil, let it cook without stirring, which affects the temperature of the mix and interferes with water evaporation. When you do stir in the nuts, do so slowly -- too much agitation breaks the sugar crystals apart. The exception to the "go slow" rule happens after you add baking soda to the mix. At that point, spread the mixture out quickly into the cooling pan before it begins to harden.