Is self-raising flour the same as plain plus baking powder?

 Do you want precision in your baking, or to avoid faff when you want your dough to rise? Here’s where baking really becomes chemistry …

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Weighing up your choices: if you use plain flour, at least you know how much raising agent you’re putting in if you need to use it. Photograph: Lucy Lambriex/Getty Images

Why do some recipes specify self-raising flour and others plain flour and baking powder? Can I replace one with the other?
Lily, Manchester

“I’ve often wondered why people select self-raising flour,” says John Lister, founder of British miller Shipton Mill. His conclusion? A combination of convenience, tradition and classic recipes (hello, sponge cake) that call for it. “It’s a uniquely British thing,” agrees Edd Kimber, author of One Tin Bakes Easy. “We’re not the only country that uses the stuff, but we are the only country that seems to have such a unique relationship with it, which leads to questions such as Lily’s.”

Let’s back up, though, and get a quick refresher on what self-raising flour actually is. All-round baking guru Dan Lepard explains: “It’s a mixture of plain flour with bicarbonate of soda [sodium hydrogen carbonate], plus an acid powder [usually monocalcium phosphate in supermarket mixes].” And this is not an ingredient to stock up on, says Sarah Lemanski, founder of Nova Bakehouse in Leeds: “The raising agent in self-raising flour can deactivate over time, so its reliability and consistency can be a bit up and down.”

And, as we’ve noted here before, baking is alchemy. “It’s good to know how much baking powder you’re putting into a recipe, and with self-raising flour you just don’t know,” says Guardian columnist Benjamina Ebuehi, whose new book, A Good Day To Bake, is released next month. “Some recipes get you to add baking powder for extra lift, anyway, so in my opinion it just starts getting faffy.” For this reason, Ebuehi doesn’t have much truck with the self-raising stuff at all: “I’m team plain flour with baking powder; it saves space – I don’t like having two flours at home – and you can use plain flour in everything.” Plus, adds Lemanski, who also prefers plain flour plus a raising agent, you then have ample opportunity to play around with different types of flour: “You would never see self-raising rye flour [in the shops], for example.”

Of course, Lily could sub in plain flour (and a raising agent) for self-raising in her bakes, but, as Kimber points out, things can get a little tricky, because “no one really agrees on what the ratio of flour to baking powder is”. Lepard suggests either combining 250g plain flour, 10g cream of tartar and 5g bicarbonate of soda, then sifting “two to three times to mix evenly”, or simply 250g plain flour plus 15g baking powder (or about three teaspoons). Lemanski, meanwhile, adds a smidge less (“5% of the weight of flour should be baking powder”); Nigella Lawson on Nigella.com goes for 150g plain flour plus two teaspoons of baking powder; Ebuehi 150g plain flour plus one and a half teaspoons; while Kimber admits he “changes it all the time”, because what you make and what ingredients you use will play a part, too.

“Sometimes, a recipe already contains an acidic ingredient, such as buttermilk or soured cream, so it needs only bicarb to rise,” Lepard explains. “Whereas a banana cake, where the fruit makes it very alkaline, often needs extra acidity, so additional baking powder can be helpful.” Essentially, like all of us from time to time, bakes might need an extra lift, so be prepared to experiment.

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