The Brewmaster Mixes Up Our Secret Ingredients WD-40's secret ingredients are mixed up in a giant vat by Ken, our "brewmaster." Ken's job is to manage the mixing process. He tests each batch to be sure the product trusted by users for over 45 years is made to the same absolute standard of quality. Once mixed, the WD-40 concentrate (we call it the "secret sauce") is then held in silos like these until shipped to one of the many aerosol packing facilities in the United States, and all over the world. So, what's in the concentrate??? Only a handful of people in the entire world know the answer to that. In fact, even the number of people who know is secret!