Bitters are made much like coffee is by percolating hot water over the ground up barks, herbs and grains in the basket. The actual formula is a closely guarded secret, but resultant bitters do wonders for many of today's cocktails. Making of the bitters is a relatively simple process that takes up only a small corner of the "House of Angostura".
The House of Angostura is by appointment of Queen Elizabeth II the manufacturer of Angostura Aromatic Bitters. There is a special "Diamond Jubilee" edition of the bitters that was made in very limited quantities for her 50th annaversary as the Queen of England.