By Jack Horzempa
The four basic ingredients of beer are malt (e.g., barley malt), hops, yeast and water. The malt needs to be processed, first via milling (crushing the malt) and then a mashing process to convert the starches in the malt to sugars that the yeast can consume during fermentation. There are a number of other grains which can be used to produce beer beside barley malt, some of which are malted and others that are not. Some examples of other malted grains are wheat, rye, and oats. Examples of non-malted grains are corn, rice, and unmalted barley.
A grain mill is a piece of equipment used to crush the grains (e.g., malt) to open the malt husks, exposing the grist within the husk to ensure an efficient mashing process. Ideally you want the crush to create a balance of split husks and the broken up contents of the kernel; these contents are sometimes called grits. Having the contents exposed to water during the mash allows as much of the starches to be converted to sugars via enzymatic processes.
If the wort (i.e., the sugar water) is separated by lautering there is a need for some intact husk material to create a filter bed for proper liquid separation to occur. For homebrewers who mash using the Brew in a Bag (BIAB) process the need for intact husk material is not as great since the grain bag operates as the filter bed.
Below is a photo of crushed malt illustrating the combination of split husks and grits of the kernel:
I started homebrewing in the 1990’s and my Local Homebrew Store (LHBS) had a grain mill they placed in a back room which was free to use for their customers. They would let you select your grains at whatever amounts you wanted (e.g., fractions of a pound), weigh them on a scale which would be noted and then combine those grains for milling. I would buy my grains and mill them on a per batch basis. The grain mill was hand cranked (more on that later) and the milled grain would collect within a bucket. You would then pour the crushed grains into a plastic bag. This system worked for me over a decade+ but as the old saying goes all good things must come to an end. My LHBS closed so goodbye to this method of milling grains.
I started purchasing my homebrew supplies online and the online vendors would provide the option to mill the grains for their customers. This is what I did for quite some time. The less than ideal aspect here is that as the end customer I could not control the level of crush (e.g., coarse crush vs. fine crush) and other considerations. It took me a while but I finally decided to purchase my own grain mill. A decision I never regrated and something I wished I had done earlier in my homebrewing.
When purchasing crushed grains from online homebrew supply vendors these grains often have a coarse crush. The rationale here is that the online vendor has no idea how each customer lauters their mash so by conducting a coarse crush this mitigates the potential of a customer experiencing what is referred to as a stuck sparge – the larger husk material creates a filter bed that readily permits the liquid to pass through. The downside of this coarse crush is that lesser amounts of the kernel’s grits are exposed to the water during mashing and conversion efficiency is lowered. This is a classic example of a trade-off. I personally have the ability to easily lauter my mash so a coarse crush is not a good idea for my homebrewery. It very much makes sense for me to mill my own grains to optimize a better crush.
In the BIAB method homebrewers place their milled grains in a large mesh bag (often made of nylon). Since the mesh of these bags effectively are a filter, these brewers can utilize a fine crush. This will have the benefit of increasing the conversion efficiency which is a great benefit especially for those BIAB brewers who do not sparge their grains after mashing.
If a homebrewer uses a given base malt regularly it makes economic sense to purchase that product in bulk (e.g., 50/55 lb. bags). If stored properly (cool, dark and airtight containers) a bag of malt will last a long time. As a point of example, I am a fan of Weyermann Pilsner Malt so I choose to purchase that product in 55 lb. bags which I utilize in my brewing over an extended period of time (1+ years) on a batch appropriate basis. I will measure out the amount I need for a given batch (e.g., 10 lbs.) and mill that malt the day I brew that batch.
How long a malt will be ‘good’ for after milling seems to be a debate. In the past on the Briess website they listed: “…preground malts are best when used within 6 months from date of manufacture.” I have also read on the Brulosophy website there they conducted an exBEERiment using 6 month old milled malt vs freshly milled malt to brew a beer style and taste testers could not reliably taste the difference. Maybe milled grains can be ‘good’ for up to 6 months if stored properly.
I think it is safe to say that once malt is milled it is not improving with age. The analogy I would suggest is that when I utilize my black pepper grinder I do not pre-grind the peppercorns for use later, but instead grind the peppercorns right over my food since to my mind fresh is better. Since I own a grain mill I feel the same way about my homebrewing grains – I choose to mill them the day of brewing since fresh is better in my opinion.
There are a number of features of grain mills which should be considered when deciding which grain mill is suitable for each homebrewer:
In the majority of instances, the grains are crushed via metal rollers. There are some lower cost grain mills that utilize plates to effect the crush (e.g., Corona Hand Mill) but these products are best suited for small quantities of grain and will not be further discussed.
The two basic designs are two rollers and three rollers. Needless to say a three roller design will be more costly vs two rollers.
In addition to the 2 vs. 3 roller consideration is the material used to construct the roller. Choices of materials include hardened steel, cold rolled steel, and stainless steel. The benefit of stainless steel is that is resists corrosion which could be important if the grain mill will be frequently exposed to a corrosive environment (e.g., a high humidity environment).
An important feature of the roller design is to be able to adjust the gap to be able to adjust from fine to coarse crush. A question which may be asked is what is the best gap setting to choose? This will depend upon a number of factors with one being what method of mashing will be performed. BIAB homebrewers would likely select a small gap to achieve a fine crush. Homebrewer who have a mashing/lautering system that is prone to having a stuck sparge may choose to have a wider gap to mitigate the occurrence of a stuck sparge. My grain mill came with a factory setting of 0.039 inches (1 mm) and that gap setting works in my homebrewery.
One more aspect worth mentioning is that some grains require differing gap settings. Heretofore I have only crushed barley malt (base malt, crystal malt, roasted malt) so the factory setting works. If I were ever to brew with wheat malt I would need to adjust my gap to a smaller setting to accommodate the fact that wheat malt is smaller than barley malt.
Unless you are a DIY (Do It Yourself) person like my friend Billy Joe you will want to purchase a grain mill that includes a hopper to contain the grains for milling. Hoppers can come in various sizes from 7 lbs. all the way up to 39 lbs. (and sometimes even bigger). The larger the hopper the higher the cost but you obtain the convenience to put all of the grain in all at once. I have a grain mill with a 7 lb. hopper and I just add grain in two stages which is not inconvenient for me. Hoppers are typically made out of thin sheet metal.
I related how I used a grain mill which was powered by hand with a handle at my LHBS back in the day. I personally do not mind a little manual labor so using a handle was what I wanted in a grain mill. Many homebrewers prefer to not go the manual labor route and there are options here. You can hook up a drill to power the grain mill (remove the handle if it has one) or alternately you can DIY a setup using a motor/pully system. There are even some expensive grain mills that have a motor incorporated into the design. Lots of different ways you can crush it here.
A number of grain mills include a base made of wood to permit the grain mill to sit upon a bucket. I use an old bottling bucket for my setup. For the DIY types there may not be a need for a base in that you could create a table top design and just have a hole in that table to permit the milled grain to fall into whatever container you desire (e.g., bucket, plastic storage container, etc.).
How to crush it!
Some of the grain mills will specify how quickly grains can be crushed in units of lbs./minute. How quickly you can crush grains is dependent upon how the grain mill is powered. Since I choose to hand crank I do not crush my grains at a rapid rate. I have seen specs for grain mills in the range of 6-7 lbs./minute but some of the hefty models will specify much higher rates like 12-13 lbs./minutes (and even higher). It is prudent to keep in mind that you want to obtain your desired crush of some husk material along with the grits and a slower speed favors less flour production and improved husk integrity. I have read that a suggested speed when using a drill or motor is something like 175 – 200 rpm. No matter how you figure it is a matter of minutes for completing the crushing process and going too fast may result in a less than ideal crush.
I made mention earlier that my LHBS had a separate/dedicated room for where we could grind our grains. I frankly did not think about this aspect until I purchased my own grain mill and better realized the dusty nature of milling grains. I choose to mill my grains outside in my carport. I did once on a particularly cold day decide to mill in my basement but I had to use my shop vac to pick up all the resulting dust on the basement floor. I would have been better off just bundling up and milling outside. What is 2-3 minutes of cold weather in the big scheme of things.
I have read that some folks choose to wear masks like those used during the sanding of wood to protect themselves during the milling process. I personally do not do this but if you choose to mill indoors with less moving air maybe this would be a good idea.
Maintenance of your grain mill
After each use I clean my grain mill outside using an inexpensive paint brush. As has beer discussed a fair bit of dust is created and simply brushing the grain mill will remove that dust.
If you are willing/motivated to disassemble you grain mill for a more thorough cleaning it would be prudent to periodically lubricate the roller bushings with a few drops of food-grade mineral oil.
It is also a good idea to periodically check your gap setting to ensure that it has not changed with wear/use. I have feeler gauge from my time maintaining cars that had gaps which needed to be checked/adjusted (e.g., rotor/distributor cap gap setting). I suspect that most folks do not own feeler gauges and I have read that some people will use a (old) credit card to set their gaps. A credit card’s thickness is smaller than what I want for my grain mill (i.e., 0.039 inches) but for some people who prefer a finer crush this would be a good way to measure/maintain their gap settings.
What is the best grain mill?
I regularly participate in homebrewing forums and the question of “best grain mill” is a popular thread question. One participant on a homebrewing forum would post “Everybody will say that the grain mill they own is the best grain mill” and there is likely a lot of truth to that sentiment.
The prudent thing to do is to establish a budget (what are you willing to pay for a grain mill) and carefully consider which of the previously discussed features you deem necessary. Hopefully after deciding on your required features there is a product that is consistent with your budget.
I will offer up two pieces of advice here:
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