Mash and Sparge Temperature and Milling

Milling and the crush of your grain

Why do we mill the grain? You want to remove the husk and break the kernel up enough to extract all the sugar by breaking up (the endosperm) into just pieces.  Breaking up the grain not pulverize it. The finer you grind or crush the grain, the better the efficiency and extraction of sugars. The finer you crush the grain, the more “flour” you will get. Then mixing the flour and water will result in making a sticky dough and eventually “glue” that you won’t be able to lauter through.

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The grain husks act as a filter to keep the whole mash and lauter flowing and moving.  You want the husks to be left as a whole because finely shredded husks will result in an astringent off flavors and risk of tannins.

So getting a good crush is key. Produce little flour, break the kernels up, and don’t shred the husks.


  • Always mill outside to keep the dust down – Away from fermenting beer
  • Mill right before you brew to minimize oxidation
  • Use rice hulls when you are unsure of your crush, especially using wheat and rye
  • Purchase the best homebrew grain mill you can afford
  • A hopper always you to mill more grain at once, if not you’re whole grain bill
  • Set your mill roller gap to proper desired gap.
    Which from 0.5mm (0.019”) to 1mm (0.039”) with 0.75mm (0.030”) being an average.
  • Check your crush and adjust the gap as needed…Don’t wait until you’ve finished and it’s too late

Mash and Sparge Temperatures

A single step infusion mash is the most common mash technique used which is the conversions step. The main reason for mashing is the conversion step. Typically done at between 146F[63C] and 156F[69C], this conversion breaks down the complex sugars in the grains into shorter chains of sugar that the yeast can eat on during fermentation.

The temperature of your conversion step determines what percentage of the complex sugars are broken down into simpler sugars. This is from the enzymes active in the mash that break down complex sugars into simpler ones.

The two main enzymes active during the mash are the alpha and beta amylase. Alpha amylase are most active in the 154-167 F range. Which creates longer sugar chains that are less fermentable, resulting in more body in your beer. Beta amylase are most active between 130-150 F which cut off single maltose sugar units that are more fermentable. This results in a more complete fermentation, higher attenuation, a cleaner beer and a thinner body.

A multi step mash is the used to be the standard in brewing. The reason behind multi-step mashes was to develop enzymes to help in the conversion of starches. Before malting and kilning was improved most malts were described as “undermodified”. They had relatively low enzyme content as a result, and required additional steps to help enhance the enzymes.

Typically rests during the multi step mashing.

  • Phytase (86-126 F) – Lowers the pH of the mash.
  • Debranching (95-112 F) – Helps with solubility of starches
  • Beta Glucanese (95-113 F) – Breaks down the gummy heavy starches, which can help improve stability and extraction, particularly for mashes high in proteins and adjuncts such as wheat.
  • Pepidase (113-131 F) – Produces free amino nitrogen, which can aid in fermentation.
  • Beta Amylase (131-150 F) – Produces maltose, the main sugar fermented in beer.
  • Alpha Amylase (154-162 F) – Produces a variety of sugars, including maltose and also some unfermentable sugars. Mashing at the higher end of this range produces more unfermentables and therefore more body in the finished beer.

Sparging is the rinsing of the grain bed to extract as much of the sugars from the grain as possible without extracting tannins from the grain husks. Typically, 1.5 times as much water is used for sparging as for mashing. Your sparge water should be heated so that your grain bed remains at 168–170 during lautering whether you’re doing a fly-sparge or batch sparge.

To reach or maintain the 168 to 170 F sparge quicker you can add the additional step of a mash out before the start of the sparge. Performing a mash out step, while not required, will aid in the lautering because the sugary solution is less viscous at higher temperatures. And will also likely increase your extract efficiency. But keeping in mind not to exceed 170F is the most important.

Then you have BIAB. Which uses a full volume mash and does not require a sparge. With a thorough crush BIAB efficiency can be quite high, especially for lower gravity worts. Some BIAB brewers sparge by dunking their grain bag in another vessel, or by sprinkling sparge water on and through the bag as it is suspended over the kettle. Or perform a mash out and temperature increase to aid with draining of the grain bag once removed from the wort.

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