It has to do with spraying water on top of the mash bin as the more concentrated wort is removed below.<br><p><a class="external free" href="https://en.wikipedia.org/wiki/Lautering#Sparging">http://en.wikipedia.org/wiki/Lautering#Sparging</a><br>
Observing the brewing process at THAT Brewery, Pine AZ<br></p>
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