The latest volume in The Little Series of Homestead How-Tos is a comprehensive guide to understanding what baking powder is and how it works, and how to substitute for both the baking soda and acid components.
As you may know, your kitchen likely contains a lot of options for substituting the acid component, including vinegar, apple cider vinegar, lemon juice, sour cream, yogurt, whey, molasses, and honey.
Your options for substituting the carbonate component with homemade ingredients are more limited, but Leigh still tells you how to make and use them.
Of the 54 recipes the book includes, 33 use baking soda, one uses sodium carbonate, 10 use pearlash, saleratus (potassium bicarbonate), ash water, or wood ash, and three use hartshorn (ammonium carbonate). The other seven get their leavening from eggs or 'emptings,' the yeasty residue that settles at the bottom of brewing vessels, but that, unlike most yeast-based leaveners can apparently be used in quick breads like a chemical leavener. So, in some cases, it's also possible to get by without a carbonate at all. It's worth noting that with a little trial and error, you can also substitute some of the wood-ash based leaveners for baking soda, as Leigh did in a series of posts on her blog, 5 Acres and a Dream.
One of my favorite parts of the book is the table of recommended ratios for the various household acids and baking soda. i.e., how much lemon juice do you mix with a teaspoon of baking soda? How much molasses do you mix with a teaspoon of baking soda to get the same leavening effect? That's a pretty handy resource and makes substituting ingredients much easier.
The only thing I would have liked to see more of is photographs of the baked goods! There's a delicious picture of biscuits on the cover, but inside the book, there are only links for a few of the recipes that appeared on Leigh's blog, 5 Acres and a Dream. On the other hand, fewer pictures to drool over means a lower probability of a shorted-out keyboard, so maybe it was a good strategy after all.
I should mention that I received a free copy of the book, not with any expectations of a review, but, well, for simply being interested enough in the chemistry to contribute some thoughts on Leigh's blog. That said, I would have gladly ponied up the $2.99 price tag of this book. It's clear that Leigh put in many, many hours of research on this book, and three bucks is more than fair for that effort.
[Parts of this review also appeared on my blog, The Homestead Laboratory, which I copied here rather than writing a separate review.]
(reviewed 13 days after purchase)