Over on Instructables, Belsey shows how to make your own Alka Seltzer for a fraction of the cost.
As I was making bath bombs to give for Christmas I felt a little heartburn. I reached for the Alka Seltzer... Wow... $8.99 for 36 tablets! One dose is made of 2 tablets, so that comes to 50 cents per dose. Then I looked at the active ingredients. Citric acid and sodium bicarbonate. Exactly what I was using for the bath bombs! Sour salt and baking soda! I made a rapid calculation: one dose comes to 2 grams of citric acid, and 3.88 grams of baking soda. If I figure that citric acid costs $4/lb and baking soda is $1/lb, the exact same dose of alka selzer's active ingredients would cost me about 2.5 cents to make myself.... Twenty times less than the store bought version! OK to be fair, I didn't figure the cost of filler, and the store bought alka selzer also contained aspirin, but I neither needed nor wanted the aspirin. Even if you end up spending more on the citric acid and less for the Alka Seltzer than I did, you'll still come out ahead.
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. His new book is Maker Dad: Lunch Box Guitars, Antigravity Jars, and 22 Other Incredibly Cool Father-Daughter DIY Projects