The name probably comes from Polish bakers: the first to use it.
Poolish is a, fairly, wet pre-ferment. It combines one part flour to one part water ratio by weight and some yeast.
You can actually say that it is a preferment with a 100% hydration level.
Poolish is very useful in pizza dough making. It increases dough extensibility and improves taste and texture in the final product.
Typically used for baguettes and open crumb loaf of bread.
As I said, it is a 100% hydration dough, and the yeast in it is around 0.2% (always calculated based on the flour’s weight).
However, the Poolish fermenting time can be between 3 to 18 hours: the longer the time, the less the amount of yeast.
Just as an indicator you can consider a yeast amount of 0.3 g for a maturation up to 8 hours; 0.2 g for a maturation up to 12 hours; 0.1% for a maturation up to 18 (and over) hours.
It usually rests at room temperature, but nowadays, I saw many recipes that suggest keeping it in the fridge. The lower temperature allows you to leave the Poolish fermenting even for longer than the max 18 hours I mentioned before.
A 1 Kg flour recipe for Poolish could be like this:
|Strong flour||1000 g|
|dry yeast||2 g|