I get it, Diana, but even buying in bulk you'd end up paying 4 times the price of the can conveniently stocked next to the flour and sugar at your local grocery. Maybe only 2 or 3 times as much as Rumford which also solves the aluminum and GMO fears expressed on this page. No judgment intended, just pointing out a few facts.

Just countering your grocery store prices, Chef! Even if you waste most of it, you're still ahead of those.

That should raise -- what -- 500 biscuits or thereabouts?

You can get 1.2 lbs. of cream of tartar on amazon.com for $8.99 and 1 lb. of arrowroot for $3.39.

Baking powder runs about 20 cents per ounce at my local market. They want $4 per ounce for Cream of Tartar and Arrowroot. Just saying...

No additional starch needed - the arrowroot takes care of that. It substitutes 1:1 just fine.

But as Chef Ono points out, if you're going to store it after making it, you'll need cornstarch or potato starch to keep the two ingredients from reacting.

If you have any qualms about using the baking powder that contains aluminum and cannot find a brand that doesn't (or if you just run short and don't have time to go to the store), just make your own:
2 Tablespoons baking soda
4 Tablespoons cream of tartar
4 Tablespoons arrowroot
-Mix it all together and store it in the empty baking powder can you just finished! Makes just over 1/2 cup.
I have used this for years and don't miss putting baking powder on my shopping list!

If you're going to make your own -- why I don't know because it's readily available, aluminum-free and non-GMO if that sort of thing gets your panties in a bunch -- be aware the starch is there to prevent the acid and base from reacting during storage and to add bulk to aid in measuring. Without the starch, you won't be able to substitute 1:1 in a recipe written for commercial powders and you'll need to make it à la minute.

Ophelia, the discussion Alx directed us to says 2 parts cream of tartar to 1 part baking soda, which is the opposite of what you mentioned. How can we resolve, because I'd love to make my own baking powder?

I realize this was a while ago but I just wanted to say that baking powder is made from baking soda. Perhaps you would be interested to see how baking soda is made! http://www.ehow.com/how_6752224_make-bicarbonate-soda.html. This is the reason I've been looking for the same answer. I think you may be interested in answers I found here http://cooking.stackexchange.com/questions/14928/alternative-leavening-agents-other-than-baking-powder-and-their-ratios-of-subst

Hain Featherweight Baking Powder contains potato starch instead of cornstarch. It is also gluten and sodium free if that is a concern.

Agreed -- it is the metallic taste that is most objectionable, although most commercial baking powder also includes a starch to minimize clumping. Usually that starch is corn starch. Unless it is organic (has anyone seen an organic baking powder? -- if so, please share the brand), chances are excellent the corn starch came from genetically engineered corn, and many people are concerned about GE foods. Ophelia's idea of making your own is a GREAT alternative. You probably only want to make what you'll immediately use (rather than a big batch to store) as it won't include the starch to prevent the clumping...

Okay, now I'm confused. Why would you want to avoid aluminum?

Sorry, I missed the aluminum question. That's easily avoided by buying a brand like Rumford that is a long-standing classic, reliable and widely available.

The only rumor I've heard concerns the aluminum content of some baking powders. There's a hazy connection between aluminum and Alzheimer's but no evidence has ever been found to suggest aluminum causes dementia -- that all comes from people who don't understand the difference between connection and cause. Meanwhile, aluminum is the third most common element on Earth.

What have you heard is "not the best"? The only caution I'm aware of is for use of baking soda when cooking dried beans, that it may reduce the content of some of the B vitamins.