In a medium skillet, put 1/4 cup of sugar and 2.5 tablespoons of cornstarch. Mix with a spatula. Slowly add six ounces of pineapple juice and 3/4 cup raspberry juice. Stir constantly with the spatula. Heat on medium-high heat but once it begins to heat up, reduce heat to medium. Continue to stir until all is combined and clear glaze begins to form. Continue stirring until the entire mixture turns to glaze.