Mix Dry Ingredients: In a bowl, combine 1 cup flour, 1/2 cup salt, and 2 tablespoons of cream of tartar.
Prepare Colored Water: In a separate container, mix 1 cup of hot water with a few drops of your chosen food coloring (pink, purple, or red) and 1 tablespoon of oil. Add the vegetable glycerin here as well.
Combine and Cook: Gradually add the colored water to the dry ingredients, mixing as you go. Continue mixing, if your dough is still very dry slowly add the remaining 1/2 cup of hot water. You may not need all the water, so add it slowly until you reach the desired consistency.
Knead the Dough: Once the mixture is combined and cooled down a bit, knead the dough. You can do this by hand or use a stand mixer with a dough attachment for a smoother texture.
Adjust as Needed: If the dough is too sticky, add a little more flour. If it's too dry, add a bit more water. The perfect playdough should be smooth and not leave residue on your hands.