What is glass in? How to use in English

The phrase "glass in" is a popular term used in the beer industry, specifically to denote a state where beer has been conditioned or aged in glass bottles for a certain amount of time. This process is also commonly known as bottle conditioning, which refers to the introduction of live yeast into the beer, allowing it to continue fermenting in the bottle. The origin of the term "glass in" can be traced back to the traditional English brewing practice of storing beer in wooden barrels for maturation. During the 1970s, a new method emerged, whereby brewers started transferring beer from wooden barrels to glass bottles for secondary fermentation. This immediately led to the coinage of the term "glass in," owing to the glass bottles used for maturation. The process of bottle conditioning became increasingly popular due to its ability to impart unique flavors and aromas to beer, often adding a sweetness and fruity notes that would have been stripped out otherwise during the primary fermentation phase. Craft brewers around the world now routinely use "glass in" techniques to create unique beers with distinct flavor profiles. In summary, "glass in" is a useful industry term that highlights the secondary fermentation process of beer using glass bottles for maturation.