Amount of cream of tartar to prevent crystallizing of sugar?

To prevent crystallization of sugar when making candies or syrups, you can add about 1/8 teaspoon of cream of tartar for every cup of sugar used. This acid helps to invert some of the sugar, which reduces the likelihood of crystals forming. Stir it in well with the sugar and liquid before heating. Adjust the quantity as needed based on the specific recipe.