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The wort is mashed and sparged as normal (and alternatively brought to a short boil), and is then lowered to somewhere between 109-115°F (42.8-46°C). This temperature favors ''Lactobacillus'', while discouraging Enterobacteriaceae. Optionally, the mash pH can be lowered to 4.4 with lactic acid or acidulated malt to further discourage Enterobacteriaceae activity. Once the desired temperature (and optionally pH) is reached, the wort is then transferred to a second vessel such as a glass carboy. A pure culture of ''Lactobacillus'' can be pitched, or a handful of fresh malted unmilled grain is added. The vessel should be filled to the very top, minimizing the oxygen levels inside the vessel. The vessel should be stored in a heated environment that maintains a temperature between 109-115°F (42.8-46°C) for 1 to 3 days depending on how much acidity the brewer wants (the faster the souring process the better; Jeff Young from Blue Owl achieves the desired acidity in about 18 hours usually) <ref name="young_grains"></ref><ref name="james_spencer">[http://beerandwinejournal.com/sour-wort-berliner/ Spencer, James. December 15, 2014. Beer and Wine Journal.] </ref>.
Once the 1 to 4 day time period has been reached, the wort is transferred to the boil kettle and boiled as normal. Boiling will kill all of the microorganisms in the wort, and will provide the option for adding hops and other kettle additions. Just as with kettle souring, the wort doesn't have to be boiled, but can be instead heat pasteurized at 140°F 180°F (60°C82°C) for 15 minutes <ref name="pasteurization" /> if a yeast contamination produced a significant amount of alcohol. Once boiled or pasteurized, the wort can be chilled and handled in the same way as the above methods for wort souring.
[http://beerandwinejournal.com/sour-wort-berliner/ James Spencer provides an article] that fully explains his process, as well as a step by step video guide and tasting on Beer and Wine Journal <ref name="james_spencer" />.