1 16 oz box baking soda
1 cup cornstarch
1 1/4 cups COLD water
In a large microwaveable mixing bowl, combine soda and cornstarch. In a separate 2 cup measuring cup combine water and food coloring. Stir to distribute coloring evenly. Pour colored water into soda mixture. Stir until smooth.
Microwave on high for 4 minutes. Or until mixture is stiff but can still be stirred. Stop after each minute and stir, then microwave another minute, stir, etc till stiff. Cover with a damp towel and let cool. Knead it until smooth. Store in airtight containers or plastic baggies.