Lambic is generally brewed from a grist containing approximately 60–70% barley malt and 30–40% unmalted wheat.
The wort is cooled overnight in a shallow, flat metal pan (generally copper or stainless steel) called a coolship where it is left exposed to the open air so more than 120 different types of microorganisms may inoculate the wort.
This cooling process requires night-time temperatures between -8C (18F) and 8C (46F).
While this cooling method of open air exposure is a critical feature of the style, the key yeasts and bacteria that perform the fermentation reside within the breweries' timber fermenting vessels.
Over eighty microorganisms have been identified in lambic beer, the most significant being Saccharomyces cerevisiae, Saccharomyces pastorianus and Brettanomyces bruxellensis.
The process is generally only possible between October and May as in the summer months there are too many unfavourable organisms in the air that could spoil the beer.
In Brussels dialect, lambic produced after this traditional brewing season is referred to as bezomerd, meaning that it has had "too much summer".
Climate change is further shortening this limited brewing window: in the early 1900s, lambic brewers enjoyed roughly 165 days a year in the ideal temperature range, whereas by 2018 that number has shrunk to 140.

Since at least the 11th century, and probably earlier, hops have been used in beer for their natural preservative qualities as well as for the pleasant bitterness, flavour, and aroma they impart.
Since the method of inoculation and long fermentation time of lambic beers increases the risk of spoilage, lambic brewers use large amounts of hops for their antibacterial properties.
Lambic in the early 19th century was a highly hopped beer, using 8–9 g/l of the locally grown Aalst or Poperinge varieties.
Modern lambic brewers, however, try to avoid making the beer extremely hop forward and utilise aged, dry hops which have lost much of their bitterness, aroma and flavour.
Consequently, lambics often have a strong, cheese-like, "old hop" aroma, in contrast to the resiny, herbal, earthy hop bitterness found in other styles.
The favourite hop used for lambic in the nineteenth century was a variety called Coigneau which was cultivated in the Aalst-Asse area in Belgium.

After the fermentation process starts, the lambic is siphoned into barrels, mostly old port wine or sherry barrels (of chestnut or oak) from Portugal or Spain.
Some brewers prefer used wine barrels.
The lambic is left to ferment and mature for one or several years.
It forms a velo de flor of yeast that gives some protection from oxidation, in a similar way to vin jaune and sherry; the barrels are not topped up.
Lambic is generally brewed from a grist containing approximately 60–70% barley malt and 30–40% unmalted wheat. The wort is cooled overnight in a shallow, flat metal pan (generally copper or stainless steel) called a coolship where it is left exposed to the open air so more than 120 different types of microorganisms may inoculate the wort. This cooling process requires night-time temperatures between -8C (18F) and 8C (46F). While this cooling method of open air exposure is a critical feature of the style, the key yeasts and bacteria that perform the fermentation reside within the breweries' timber fermenting vessels. Over eighty microorganisms have been identified in lambic beer, the most significant being Saccharomyces cerevisiae, Saccharomyces pastorianus and Brettanomyces bruxellensis. The process is generally only possible between October and May as in the summer months there are too many unfavourable organisms in the air that could spoil the beer. In Brussels dialect, lambic produced after this traditional brewing season is referred to as bezomerd, meaning that it has had "too much summer". Climate change is further shortening this limited brewing window: in the early 1900s, lambic brewers enjoyed roughly 165 days a year in the ideal temperature range, whereas by 2018 that number has shrunk to 140.
Since at least the 11th century, and probably earlier, hops have been used in beer for their natural preservative qualities as well as for the pleasant bitterness, flavour, and aroma they impart. Since the method of inoculation and long fermentation time of lambic beers increases the risk of spoilage, lambic brewers use large amounts of hops for their antibacterial properties. Lambic in the early 19th century was a highly hopped beer, using 8–9 g/l of the locally grown Aalst or Poperinge varieties. Modern lambic brewers, however, try to avoid making the beer extremely hop forward and utilise aged, dry hops which have lost much of their bitterness, aroma and flavour. Consequently, lambics often have a strong, cheese-like, "old hop" aroma, in contrast to the resiny, herbal, earthy hop bitterness found in other styles. The favourite hop used for lambic in the nineteenth century was a variety called Coigneau which was cultivated in the Aalst-Asse area in Belgium.
After the fermentation process starts, the lambic is siphoned into barrels, mostly old port wine or sherry barrels (of chestnut or oak) from Portugal or Spain. Some brewers prefer used wine barrels. The lambic is left to ferment and mature for one or several years. It forms a velo de flor of yeast that gives some protection from oxidation, in a similar way to vin jaune and sherry; the barrels are not topped up.
Lambic