Catchy title eh?
A lot of UK recipes call for self-raising flour. Self-raising flour is nothing fancy – it’s just plain (all-purpose) flour with a chemical raising agent, baking powder, already in the mix.
Self-raising flour was invented by Bristol baker Henry Jones, who patented it in 1845. It played a role in phasing out the notoriously solid ship’s biscuits and replacing them with an alternative: chemically leavened “bread” baked fresh at sea or even on the battlefront. Apparently his work was championed by Florence Nightingale and I believe self-raising flour was used to bake “bread” in the Crimean War.
I’m not sure about “bread” made with SR flour – it’d be much more like soda bread or scone that real bread – but it’s useful stuff for cakes and the like. A lot of bakers, however, prefer to just use plain flour then add the raising agent separately. This makes sense, as the chemicals in raising agents can lose their potency making resulting cakes inconsistent. Or home bakers might just have run out.
If you don’t have an SR flour, it’s easy to convert plain and use that in its place. Though as with so many of these things, online information isn’t always in agreement. So I’m going to work it out for myself.
Varying sources say: add 1 teaspoon to 110g, or 2 teaspoons for 150g (1t to 75g), or 2 1/2 to 500g flour (that is, 1t to 200g), and, in that strange world without sane metric measures, another says 2 teaspoons to a cup.
Converting one US cup of flour into grams is open to disagreement too. Online sources give the flour weight as between 120g and 150g. I’ve got a cup measure – marked as 236.64ml, the customary US cup size* – and in a very scientific experiment involving filling it with flour, tapping it to settle it then smoothing off the top, I got 144g. Then I did it again and got 133g. This variable is due to how compacted the powder is, and is one of the reasons using weighing your ingredients is, frankly, more accurate. So anyway, let’s say 140g. So 2t to one cup is 2t to 140g (or 1t to 70g).
Then there’s the whole question of how many grams are in a teaspoon of a powder like baking powder. Again, sources differ online. But a teaspoon is 5cc/5ml (even in the US it’s basically the same, 4.92892159375ml**). Doing another quick, very scientific experiment, I filled my 5ml teaspoon measure with baking powder, smoothed it off, and weighed it. I did the same with baking soda. Both came in at just shy of 5g, so 5g is good enough for me.
Now, I work in decimal and percentage terms, having grown up with silly old ounces and whatnot but left them behind when I discovered the comparitive simplicity of metric measures. It’s so much easier when you’re converting and scaling recipes too.
The percentages you want of the above suggestions of teaspoons per grams would be based on the combined weight of the two ingredients, ie how many percent is 5g (1t) baking powder of the 115g of flour plus baking powder?
Here are all the abovementioned amounts in percentage calculations:
5g of 75g = 5 ÷ 75 x 100 = 6.7%
5g of 80g = 5 ÷ 80 x100 = 6.3g
5g of 115g = 5 ÷ 115 x 100 = 4.3%
5g of 205g = 5 ÷ 205 x 100 = 2.4%
Personally, I’m inclined to split the difference, and indeed some older notes of mine say 4%, and another person online breaking it down comes out with 4.5%. So averaging out the above figures, you get 4.9%. For the sake of ease, let’s say 5%.
So if a recipe calls for 250g of self-raising flour, and you only have plain, you need 5% of that 250g to be baking powder. That’s 12.5g of baking powder. So 12.5g BP added to 237.5g plain flour makes 250g stand-in self-raising flour. Even a digital scale, however, doesn’t usually do half grams, so let’s say 12g to 238g. And if you really want to short-cut it, just use 2 well-filled teaspoons to the 238g.
* A US legal cup is 240ml, an Australian/NZ etc cup is 250ml.
** Technically a US teaspoon relates to another strange archaic measure – it’s 1/3 US fluid dram.