Which type of ales are created using spontaneous fermentation methods?

Spontaneous fermentation is a unique brewing process characterized by the use of wild yeast and bacteria present in the environment rather than cultured yeast strains. This method is most commonly associated with sour ales, which are known for their tart and sometimes funky flavors resulting from the natural fermentation process.

In the case of sour ales, the fermentation typically occurs in open vessels where the unboiled wort is exposed to the air. This allows ambient microorganisms, particularly wild yeasts like Brettanomyces and various lactic acid bacteria, to inoculate the brew, leading to the development of complex sour characteristics over time. This is in contrast to other types of ales, which generally rely on controlled fermentation with specific yeast strains that produce cleaner and more predictable flavor profiles.

While stouts, pale ales, and wheat ales may feature some sour elements or have sour variants, they are typically produced through conventional fermentation methods and do not rely on the spontaneous fermentation process to develop their primary flavor characteristics. Thus, sour ales stand out as the type of ales primarily created using spontaneous fermentation methods.