John Sepich offers a substantial possible explanation to this question on p. 120 in his magnificent book Notes on Blood Meridian. Sepich, referencing Carol A. Hill, one contributor to the Firefox article Powder, Flint, and Balls, writing of Hill’s account, says that “the liquid matter in the leaching process is at one stage called ‘Mother Liquor’ or ‘beer’ (254), terms perhaps related to McCarthy’s mention of the judge and Delaware Indians appearing to be drunk (perhaps on fumes) after the leaching process, ‘but on what none could surmise’ (128).”
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For my part, as I think about this episode a little more, I’ve been working on this idea that the judge’s ritualistic preparation of the gunpowder is in many ways analgous to the process and ideation involved when Vedic priests would prepare the hallucinogenic drug Soma and ingest it in order to more easily connect with God or the divine. The preparation of soma, some accounts say, involved an extraction process as it did when the judge was making the gunpowder, which connects the judge to his self-professed divinity — war. I see a sacramental component in both the judge’s work and the Vedic priests.
John Greenleaf Whittier wrote an interesting poem about soma in which he uses the verses about Vedic ecstasy to argue against the loud, emotionalism in the evangelical, tent-revival style of religion popular at the time he wrote the poem in 1872. Similarly, Holden uses words to argue against this style when he takes down Rev. Green in his tent early in the book. Those are a few of the connections I’ve made between soma and the gunpowder in BM. Here’s ehe Whittier poem, Brewing of Soma: http://www.qhpress.org/quakerpages/qwhp/soma.htm