To my surprise amazement astonishment I have just discovered that the small container of baking powder that costs about five dollars in the grocery store consists of corn starch, baking soda and something called monocalcium phosphate (which Wikipedia tells me is a chemical compound used for fertilizers and as a leavenng agent.)
To my surprise amazement astonishment horror , as I was checking the fact of these ingredients on the baking powder container in my cupboard, I noticed that it advised only keeping it a year or until best-before date.
Mine is more than four years old! My baking has been rising. How high was it rising three years ago?! How high will it rise when I get fresh baking powder?!
I also discovered (googled) that you can make your own baking powder – 1 tsp cream of tartar, 1/2 tsp baking soda, 1/2 tsp cornstarch.
Maybe I had better contain my skepticism/elation until I discover how much cream of tartar costs.