The brewing process of lambic is quite different from that of our Patience beers. When brewing top-fermenting beers, the brewer wants to deliver the same product over and over again. It is therefore important to work as sterile as possible and let only one, specifically selected yeast determine the flavor.

With spontaneous fermentation beers, nature plays a massively important role. The complex and diverse mix of yeasts and bacteria present in the brewing room and environment will make it a complex and sour beer. Each brew will taste different. Not everyone is allowed to call their spontaneously fermented beer Oude Gueuze, Oude Kriek or Oude Lambiek. There are strict rules attached to this. Those who respect these are allowed to put the European GTS label on their bottles. Some important rules:

Among the ingredients, min 30% unmalted wheat should be used and vintage hops.

Further fermentation and ageing must take place in wooden barrels.


Fertilisation of the lambic wort should be done in an open cooling vessel – coolship


The lambic wort must be brewed in the lambic region to qualify under the Geographical Traditional Speciality.

Want to find out more about Oude Gueuze and Oude Kriek? Then click here

Perhaps you have ever heard talk of brewers and ‘blenders’? Find out more about this unique phenomenon in the lambic world here.


Instead of cooling the boiling wort quickly and sterile, it is pumped onto a large, shallow, open tank (the coolship). The wort is allowed to cool quietly here overnight.

During cooling, the wort is fertilized with a variety of wild bacteria
(e.g. lactic acid bacteria) and yeasts (e.g. Brettanomyces Bruxellensis/Lambicus). The Pajottenland, Brussels and the Senne Vallry are home to a specific mix of micro-organisms that give our lambic beers their unique aroma profile.


Once the wort has cooled overnight on the open cooling vessel and fertilised, the beer is drawn onto oak barrels and foeders and the yeasts and bacteria present can get to work.

The initial fermentation typically starts up within the week in full force, with, as a reassuring sign, the typical foam bubbling up from the wooden barrels and foeders via the open tap hole at the top.

After the fierce initial fermentation, other micro-organisms take turns in ageing the lambic. During the following months and years, for example, lactic acid is formed by lactic acid bacteria and wild yeasts provide the typical wild aromas of lambic. These latter organisms also ferment the very last sugars in the lambic. So we get a very dry, fresh-sour, wild and complex beer.


The weather is different on every brew day, but also every barrel and foeder exerts its own influences on the evolution of lambic. The art of lambic blending is to put together each blend, each beer, as balanced as possible from all these different lambics and have all the flavours nicely intertwined. It has been a tradition to buy many different lambics and experiment with own blends.

With lambic beers, a distinction is therefore made between lambic brewers and lambic stekers/blenders. The word steken means blending:

  • Brewers produce their lambic wort themselves and let it mature on wooden barrels into lambic.
  • The blender buys lambic wort or matured lambic from 1 or more brewers and let it ferment and mature on his barrels. So they can usually choose from lambic from different producers to blend.

It is important to note that brewers are also stekers but stekers are not necessarily brewers.


In an Oude Gueuze, old and young lambic are blended. According to GTS rules, at least 3 years old lambic must be present in the blend. The young lambic still contains many live yeasts that convert the sugars still present into CO2. Result: a sparkling Oude Gueuze

For an Oude Kriek, whole cherries with kernel are first macerated for 6-9 months in a blend of young and old lambic, after which the cherry lambic is separated from the fruit.

This cherry lambic is reblended with young lambic and drawn in the bottle. After a refermentation in the bottle, we get a sparkling Oude Kriek.

Eylenbosch Oude Gueuze

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