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Crush Analysis

I bought a new grain mill the other day. Obviously, I had an itching desire to run a little grain through it as soon as I got it assembled. While I was at it, I figured this would be a good time to compare a couple different gap settings and the resulting crush.

So I fired up the mill to make 4 samples: 0.035 gap, 0.025 gap, and a repeat of those two, but with grain conditioned with 2% water by weight. Read this to find out why you should be conditioning your grain.

The samples were then run through a standard ASTM sieve analysis. The screens used were 3/8″, #4, #8, #12, #18, #20, #30 and #40. The mill is a standard homebrewer 2-roll mill driven by an electric drill.

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Screens and scale

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Tap machine

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#8 - large husks

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#12 - shredded husk and large chunks

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#18 - large grits

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#20

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#30

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Flour (-40)

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Results. Numbers given are % of total recovered, rounded to nearest 0.1

Much has been said about the crush, but here’s some hard evidence of the benefits of malt conditioning. The amount of in-tact husk material, beneficial for lautering, is radically different. Otherwise, there wasn’t a whole lot of variation.

I’d like to repeat the test, performing sieve analyses on multiple samples for each setting, and replacing the 3/8″ and #4 sieves with #60 and #80, to see how much of the fine material that passed through the #40 was fine grits, as opposed to dust.


1 Comment

  • Johnny Mop says:

    Very cool.. but how does a home brewer come into possession of a rotap? Last time I saw one of those… whew I cant remember its been so long.

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