2 cups baking soda
1 cup cornstarch
1 1/4 cups cold water
Mix the baking soda and cornstarch in a saucepan
Add the water gradually and stir until smooth
Cook over medium heat, stirring constantly
Continue cooking until the mixture thickens like mashed potatoes
Remove from heat and let it cool slightly
Knead the mixture on a clean surface until smooth
Add a little cornstarch if it feels too sticky
Store in an airtight container or plastic wrap when not in use