Lambic in short.
Lambic is the mother of all our beers. Lambic is great to drink, but usually the 'flat' beer serves as the base for geuze and other derived beers such as kriek and other fruit lambics.
Lambic is the result of a long brewing process with malted barley, raw wheat and old hops. But what makes the specific beer style even more recognizable than the ingredients is the completely spontaneous fermentation and the slow ageing in oak barrels. Time plays a major role in every step of the process.
It already starts with brewing. The sub-processes of mashing, filtering and boiling, including the turbid mash method, takes longer than any other beer styles. At the end of the long brewing day, the wort is placed on a coolship, exposed to the air, to cool and rest overnight.
But “resting” is relative. The wild yeasts and microorganisms, which naturally float in the ambient air, are now starting to act in on the wort. That inoculation or “conception” is crucial for fermenting the beer - no yeast is added. That is also the reason why the brewing season in the lambic world only runs during the months with cold nights (< 8°C), typically from November to early-May.
In the morning, the wort goes into oak barrels, where it will evolve into a proper lambic. Young lambic has been in barrels for at least one year, half-old lambic about two years and old lambic at least three years.
The young lambic still contains residual sugars from the brewing and is still quite active due to the wild yeasts. That gives it the potential to continue fermenting, which will also happen if we bottle it (blend) it with older lambics. They, in turn, provide complex aromas and flavors due to the'slow' Brettanomyces yeasts and the long exposure to wood.
During bottle ageing, the blend evolves into a sparkling Geuze, but from then on, it becomes a different story. Lambic itself remains a flat beer, as the carbon dioxide formed during the alcoholic fermentation can always escape through the staves of the barrel.