What’s the Difference Between Flours for Baking?

*Updated July 2025 to include new FAQs, clearer flour comparisons, and baking substitution tips.*

Flour is one of the most essential ingredients in baking – but knowing which flour to use for cakes can make or break your bake. Should you reach for plain flour or self-raising? And what even is cake flour?

Here’s a quick, helpful guide to the different types of flour used in cake baking – including tips on when to use each one, how to swap flours in recipes, and the difference between corn flour and cornstarch.

Plain Flour vs Self-Raising Flour

Plain flour (also known as all-purpose flour) is milled from wheat grain and typically has the bran and wheat germ removed, resulting in a smooth, versatile flour. It's often used for:

• Cakes

• Pastries

• Biscuits

• Sauces

However, plain flour doesn’t contain any raising agents, so it needs to be combined with baking powder or bicarbonate of soda when used in cakes.

In contrast, self-raising flour includes a raising agent already mixed in – typically baking powder – and sometimes a touch of salt. This helps cakes rise consistently without needing to measure out extras.

At Sponge, we use high-quality self-raising flour in all our cakes to ensure a perfect rise and texture in every sponge. 

Can You Substitute Plain Flour for Self-Raising Flour?

It’s best not to switch between plain and self-raising flour unless you know how to adjust the recipe. Why?

Because the ratio of raising agent matters – and self-raising flour has a precise amount blended in:

• Roughly ½ tsp of baking powder per 100g of plain flour.

Swapping one for the other without adjusting the rest of the recipe could result in a cake that’s flat, dense, or overly risen.

Why We Use Self-Raising Flour in Sponge Cakes

Consistency is key when baking in batches. We rely on self-raising flour with added sodium bicarbonate to make sure every cake bakes with the same rise and texture.

It’s part of our commitment to:

• Perfectly risen cakes every time

• Reliable recipes that work for every occasion

• Using British ingredients and supporting British producers

What About Gluten-Free Flour?

To bake our delicious gluten-free sponge cakes, we use a specially blended gluten-free self-raising flour made from:

• Rice

• Potato

• Tapioca

• Maize

• Buckwheat

This mix gives the same beautiful rise and texture as our regular sponges – just without the gluten.

Our vegan cakes use the same self-raising flour too – but with soya milk and other plant-based swaps.

Corn Flour vs All-Purpose Flour – What’s the Difference?

Though both can be used in baking, they behave very differently.

Cornstarch vs Corn Flour

These two sound similar but serve different purposes:

• Cornstarch: a white, chalky starch extracted from corn endosperm. Used to thicken sauces, custards, and gravies.

• Corn flour: milled from the whole corn kernel. Slightly yellow, it contains fibre, protein, and starch, making it suitable for gluten-free bakes.

If you’re using corn flour in cake baking instead of an all-purpose flour, you may need to add extra liquid (like milk or water) to prevent a dry sponge.

Flour Shelf Life: Why It Matters

Self-raising flour contains raising agents that lose potency over time. So, it’s important to:

• Check expiry dates before baking

• Avoid using old self-raising flour in cakes, as your sponge may not rise properly

Plain flour typically has a longer shelf life because it doesn’t contain rising agents.

At Sponge, we go through self-raising flour so quickly that freshness is never an issue – every batch bakes to our high standards.

FAQs: Choosing the Right Flour for Baking

What’s the best flour for sponge cake?
Self-raising flour is ideal for a light, airy sponge with consistent rise – that’s why we use it in all our cakes.

Can I make cake flour at home?
Yes – blend plain flour with a bit of cornflour to lower the protein content. (Roughly 1 tbsp cornflour per 100g flour.)

Is corn flour gluten-free?
Yes – but it behaves differently in baking. Be sure to test and tweak recipes if using it as a substitute.

Is it safe to use out-of-date flour?
It’s best not to. Especially with self-raising flour, expired raising agents can mean your cake won’t rise properly.

Final Crumb of Advice

The best flour for cake baking depends on what you’re making – but if you’re after consistency, lightness, and a perfect rise every time, self-raising flour is our go-to.

Ready to taste the difference? Order one of our sponge cakes made with love (and the perfect flour), send a cake card to someone you love, or jazz up your picnic or beach day with our new, limited edition beach hut baby sponges.