Joyce's Blue Ribbon Brittle

In a medium saucepan, combine sugar, light corn syrup and water. Bring to a boil. Reduce heat to medium and cook to the light caramel stage, about 320°F on a candy thermometer, stirring occasionally. Using a pastry brush moistened with water, wash any crystallized sugar from sides of pan back into mixture . Remove sugar mixture from the heat; add butter and baking soda, stirring to mix well. (Mixture will foam.) Add peanuts, stir until mixed and pour onto a well greased baking sheet. Allow to cool and harden. Break into pieces of desired size.