So you’ve made some fruit scones or peach cupcakes and you notice that the end product is streaked blue and green. Sound familiar? In almost every case, it’s not you, it’s your baking powder. Baking powder with aluminum in it reacts to acidic ingredients, causing this discoloration and what many people find to be a “tinny” or metallic taste. Fortunately, this is as easy to rectify as ditching your baking powder for an aluminum-free brand, such as Rumford (the brand also makes Clabber Girl baking powder, which, oddly, does contain aluminum) or Bob’s Red Mill.