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A malt mill is fundamental to the brewing process. Malted barley holds all our extract and enzyme needs, but they are locked away in whole malt. We need to crush or mill the grain to gain access.

It’s not a case of any mill will do. The malt must be carefully ground to ensure maximum extract while keeping the husk intact to avoid wort filtration issues. Not all mills are equal, and an agricultural mill is not the same as a purpose-built malt mill, so you must choose wisely, or you won’t get the grind you need to maximize the brewhouse potential fully.

Malt mills can be a simple 2-roller mill or a mega complex 6-roller. The extra rollers allow you to maximize the extract while keeping the husks intact, maintaining filtration performance. You would use these kinds of mills for malt with a low friability. The measure of friability is the ease with which the malt can be crushed, and the friability value on the CoA (Certificate of Analysis) will tell you how well modified the malt is.

The malts need to have homogenous grain size for efficient malting and subsequent milling. During the malting process, the grains will modify at different rates, resulting in varying levels of modification. In the mill, smaller grains may fall through the gaps without being ground.

Luckily, UK malt is lower in nitrogen and generally well-modified, making it nice and friable so that simple malt mills can produce excellent results.

Sam Fraise from Attic Brewery tips out malt from a Crisp branded bag ready to be milled for brewing.

Sometimes, you have no option on the kind of mill you have, and you need to run with it. So, what is the process of adjusting the mill to make the brewhouse sing?

It’s a simple process, but you need some background information first. You need a starting point, so gather the following:

  • Current extract from each brew
  • Filtration times
  • Wort clarity expectations
  • Fermentation performance
  • Grist fractions
  • Current mill gaps

You need a starting point to ensure that the changes you make are worthwhile, and you also need a reset point to return to should things go wrong. 

Extracts and fermentation times are easily recorded on the brew sheets, and fermentation performance on the profiles. Clarity can be subjective, so experience will play a big part, but keep an eye on the cold break and the residue left in the kettle or whirlpool. This is the best indication. Grist fractions can be easily and quickly checked using a grist box, and the mill settings can be checked using a feeler gauge. When you check the mill gaps, pay attention to the whole length to make sure there are no differences. Rollers can be misaligned, and they do wear, this can influence the milling performance.

Once you have all this information, begin to adjust the mill gaps. You don’t need a massive adjustment, start by pulling them in by 0.05-0.1mm and check the grist analysis and the mill gaps along the full length of the rollers. Mill the whole grist and then brew the beer paying close attention to everything above.

Continue to adjust the mill until you go a little too far and start seeing some issues, if you return it to the last setting, you can consider the mill optimized.

It’s important to check the grist fractions, but not pay too much attention to them while you are in the process of optimizing. Don’t worry about what you read in books, every brew kit is different, and you will be using different process parameters. I spent way too much time trying to get the perfect lauter tun grist fractions on a mill that was just not capable of achieving them.

Once you have a setting you are happy with, the grist fraction becomes important. This is the setting you revert to when you have a crop year change, and the size of the barley may be bigger or smaller. The mill gaps are just for reference, in this case, match the grist fractions.

Milling Crisp Malt for brewing

What are the risks of an incorrect mill setting?

Too FineToo Coarse
Wort filtration issues – extended timesLoss in extract
Poor wort clarity leads to issues downstream
Excessive trub from increased solids leads to raging fermentations
Potential mill damage

A fine grind can cause some broader issues, so it’s essential to find the point where you get maximum extract with minimum issues. Interestingly, some brewers have moved to a fine grist with the addition of rice hulls to improve filtration performance. With the high malt costs, the increased extract can more than pay for the use of rice hulls. 

So, you use pre-crushed malt from the maltster and are looking to install your own malt mill. What do you need to consider? 

The main reason for installing a mill is described above: you can optimize the crush to be bespoke for your brewhouse. This will save malt and money. You will also save on the crushing fee. There are some potential negative impacts. There’s a health and safety impact; you are introducing an explosion risk that needs to be managed. You also need to think about the mill capacity and hourly milling rate. Some mills are slow and can take up much of the brewer’s time to load the mill. This extra labor cost can take away any savings from the increased extract. 

Why is Crisp Crushed Malt so consistent? 

The Crisp Malt standard crush is perfect for the single infusion mash tun. We maintain this by combining operational experience with state-of-the-art milling and packaging facilities. All our operators are highly trained and follow strict procedures, checking the grist analysis on every batch of crushed malt. The crushed malt is sent to the lab, and the ‘as is’ extract is tested against the extract in the lab mill. This allows us to make instant changes to maintain the crush consistency. 

From the silo, the malt is screened to remove any unwanted material and passed through a de-stoner and magnet. We don’t want any sparks! The mill is a 4-roll Buhler with servo control, allowing us to set the roller gap width easily. The records we keep will enable us to change the settings for the different malts we mill quickly. Different varieties have different grain sizes, with Maris Otter malt being smaller than more modern varieties and Chevallier malt being larger. In comparison, oats are very small! 

Should I install a mill or upgrade my mill? 

Only you can answer that question. Consider the potential increase in extract along with saving the crushing fee against any of the negative effects, including the space it takes. The cost of the mill is not that large, but the installation costs could be significant. With modern malt sacks, there is no argument about how fresh the malt stays; they allow the malt to breathe so they don’t pick up moisture.  

It’s common for brewers to get better extract when using Crisp Crushed malt over milling it at the brewery. But the standard crush may not be perfect for your brewery, if not get in touch and have a chat, we may be able to do something to help. 

Watch our All About Milling webinar, where Mike Benson discusses all the technical aspects of milling our brewing malts.

For a more technical approach, refer to our Crisp Guide to Milling Malt, which is aimed at brewers, quality managers, and brewery managers who want to understand the art and science of milling malt.

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