It are not the kettles that make the beer, it are the malt baker and the brewer.
Bert creates an individual recipe for each single beer. The homemade malt is the basis for a secret composition of ingredients, called a “BOM package”. On the basis of that secret recipe Bert himself brews in the kettles that he hires as a gypsy brewer. He follows up the whole brewing process himself, from A to Z.