Snuffy \"Hub Cap\" McKinney wrote, on Mon, 12 Jan 2015 13:48:29 -0800:

Just bought some yesterday...
www.argostarch.com Walmart 15oz $1.67

The cornstarch is optional, and only really
needed for storage.

If I make the baking powder on the fly,
there should be no need for cornstarch.

What I REALLY need is the powdered acid,
whether it's calcium phosphate or potassium
hydrogen tartrate (KC4H5O6) from wine casks.

There is none of this at Safeway, Trader
Joes, or Whole Foods.

Are you saying that Walgreens has the
powdered acid?