NOTE: I have always stored this in a glass jar, but I heard from some people that if any moisture gets into the jar it can cause the baking soda and citric acid to react with each other and potentially explode your jar, which is why many sources recommend not storing mixtures with baking soda and citric acid in glass. I've used glass jars for this and never had this issue- you'll obviously want to keep it dry. Just be aware! If you prefer, a cellophane bag with a ribbon or twist tie would be a good option, you can also get shaker jar lids on amazon which is a great solution since the small holes allow the mixture to breath and also makes it easy to sprinkle in the sink!