Knowing when a sourdough starter is ready to use can be very tricky for the inexperienced baker – or even if you’re building a new starter.
For this reason, people have figured out ways to determine when a starter is at peak activity and ready to use. The most common way in which people like to test this is with the float test.
Some people swear by this test whilst others don’t even bother and end up with great bread, but it’s down to personal preference on this one.
Your starter likely isn’t floating due to one of a few reasons. The type of flour you’re using, the hydration of your starter, and how you handle it all affect how well it floats. AP flour, 100% hydration and gentle handling should leave you with a starter that floats. Knocking air out of it will cause it to sink.
The float test is very simple and isn’t always an accurate representation of if your starter is at peak activity. All it tells you is that it holds enough gas to be able to float. Whilst this ability to hold gas might be linked to an active starter, it doesn’t necessarily mean that it’s ready to use yet.
I’m certain that there are very weak and slow starters that take a long time to rise that still build up enough gas to float on water, but it doesn’t mean that they’re well-developed or strong enough to give you that raise you love to see in sourdough.
A dough that contains a slow and weak starter will still likely rise, but it will be extremely slow and won’t leave you with the result you would want.
The float test isn’t an ideal way to determine your starter’s activity since it’s not something that’s completely accurate and there are a lot of mistakes that can mess it up.
Although this test is far better than just guessing when your starter is at peak activity, it’s not the best way of determining it. It’s always going to be best to understand how your starter works by looking for signs as to when it’s ready.
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What Effects How Well A Sourdough Starter Floats?
There are three main components that can determine whether a sourdough starter rises or not. Some may have a positive effect and some may have a negative effect, so it’s a good idea to have an understanding of why your starter is or isn’t floating and whether it’s anything to be concerned about.
Different Types Of Flour & Levels Of Gluten
The type of flour you use has quite a significant effect on the appearance of your starter and how much gluten it’s able to develop.
Flour that contains a medium-high protein content is more likely to float than that of something like a 100% wholemeal or rye starter purely because it’s able to hold onto more gas.
When using a low protein flour in your starter such as rye, it’s not able to build much gluten so it doesn’t hold on to gas particularly well. There will be visible holes and gas production in your starter, but it’s less likely to float than a 100% bread flour starter.
Any kind of starter or dough needs enough gluten structure to actually hold the gasses. In order for a starter to pass the float test, it shouldn’t have matured to a point in which the gluten has started to break down. At this point, gas will be lost and it has no ability to float.
Although gluten may have started to break down in the mature starter, it doesn’t mean that it’s not able to properly rise your dough. Yes, the gluten will have broken down because of the acid build-up, but the bacteria and wild yeast are likely to be quite healthy and active enough to make bread.
So, although the starter might not pass the float test due to gluten deterioration, it may still be perfectly fine for leavening your dough.
The Amount Of Gas That’s Held
As previously mentioned, you need gas in your starter in order for it to float.
For this reason, you need to be very careful with it and make sure to not knock any gas out of it during handling.
Starters can very easily be degassed during handling. Whether you have stirred it or just moved it too fast, it can lose its gas in an instant.
Even the strongest and most active of starters can fail the float test if they lose their trapped gas.
Again, this is another case of a sourdough starter failing the float test but being very able to still leaven dough.
The Hydration Level
The best hydration level for a sourdough starter to pass the float test is 100%. This means that for every 100g of flour that’s added, 100g of water must also be added – a 1:1 of flour:water.
Using a hydration level that’s too high will leave you with something that’s too gloopy and won’t be able to hold any gas. Putting this starter in the water will leave you with a disappointing result. It will just break down into the water.
Keep in mind that the type of flour you use can determine how wet and gloopy your starter is. An all-purpose flour starter is going to be much wetter than a wholewheat starter since it can absorb less water.
On the other hand, a stiffer starter, which contains less water, is likely to be able to hold more gas and float in water more easily. So, whether your sourdough starter floats or not is relative to the amount of water it contains.
How To Know When Your Starter Is Ready To Use
Knowing the exact time to use your sourdough starter is a bit tricky and it is one of these ‘it depends’ kind of things.
You might want to use a young starter for a less acidic taste or a mature starter for a more acidic taste. It depends on how you like your bread, what the recipe calls for etc.
In general, there is a point where your starter reaches peak activity and it’s ideal to use it at this point for the best rise. It’s important that you get an understanding of your starter and know when it’s ready to use so you don’t have to mess on with things like the float test.
There are a few signs that indicate when a sourdough starter has reached its peak and is ready to use. Assuming your starter is 100% hydration, these signs are:
- There Should Be Some Foam On Top
Before it’s completely ready to use, the surface of your starter should be smooth, slightly domed, and it may even have some bubbles on it.
By the time it’s ready, there will likely be at least some foamy bubbles on top. These bubbles might just be around the rim or they could cover the entire surface of the dough.
- It Will Have Slightly Dipped/Fallen
At peak activity, the microbes in the flour will have just finished eating all the available food in the flour and therefore need feeding again. At this point, there is a very slight fall in the starter and it should be used as soon as possible.
This just makes sure that the starter can get straight into ‘eating’ the new flour in the bread dough and rise it more quickly.
- It Should Have Risen Significantly
You’re wanting something that’s at least doubled in size, but a healthy and strong starter will likely rise even more. Some people have starters that triple in size or even more than that.
You’re basically wanting to make sure that your starter has enough activity to properly rise and therefore leaven your bread dough appropriately.
This is how a sourdough starter should look when it’s ready to use:
Note: A sourdough starter can take a few weeks to get strong enough to rise bread properly. Continue to feed your starter 1-2 times a day for 2-4 weeks for the best results.
If the dough has been stored in the fridge for a while, feed it twice a day for 2-3 days before using so it can build up its strength again.