The two main types of mills in the craft distilling industry are hammer mills and roller mills. There are some burr mills and cage mills floating around, but if you’re shopping for one of them, you probably already know why. Roller mills are popular in the brewing industry because they do a good job of separating the husk from the malt and tend to leave a larger grist size that works well for the lauter tun (most common in the industry). Because roller mills are so common and a lot of people come to the distilling industry from the brewing industry, they are pretty common on this side of the industry as well. Typically, brewers are using two-roller mills. But is a two-roller mill right for you? If you are looking to mainly do malt and malt-like products (mainly wheat since rye is a lot smaller) or if you are doing off-grain fermentation, then the two-roller roller mill will do the job nicely for you. There are also 4- and 6-roller roller mills. These are capable of giving a finer grind than a 2-roller roller mill, or are at least doing it much quicker since you can decrease the spacing between the rollers as you go (rather than expecting a single set of rollers to do all of the work). Generally, roller mills are more expensive than hammer mills, mill slower, and require more maintenance. But they have life spans that are 4 times longer than a hammer mill and can separate out the in-fermentable husk.

Hammer mills are mainly used in the grain business and are used for making flours. Hammer mills can mill a lot of grain quickly and can make a much finer grist than is possible in a roller mill. The benefit of a finer grist is that it takes less time for the water, heat, and enzymes to act on the grain particle, which means mashing times decrease and yields increase. But finer grist will also pack tighter, increasing lautering times and even blocking off the screens. Hammer mills are also required to work with potatoes and corn, so if you’re looking to branch out with your mill, you will be better off with a hammer mill. The fine grist from a hammer mill works best with on-grain fermentations or when using a mash filter.

A mash tun is where you will be performing the conversion of starch to sugar, so it’s not needed for sugar-based spirits. Though, with most of them, a little bit of heat (less than 135°F) can help with the sugar absorbing into the water. People that have a mash tun available have been know to use it to heat the water and mix in the sugar, agave, honey, molasses, or whatever else they desire.

There are a couple of things to look for when you are converting starch to sugar: the first is what your heating mechanism is. Direct electric heat is really only useful for small kettles and generally not recommended once you get over 100 gallons. Direct steam injection, on the other hand, is the most energy efficiency mechanism. But, you will need steam that is not treated with chemicals that could hurt your mash or fermentation. And you need to account for the volume of water from the steam in calculating your water volumes. Another heating mechanism is indirect steam. It’s less efficient but allows for the use of cheaper steam. Cheaper steam is important because most plants can’t afford multiple steam systems and you will likely be using that more expensive steam in other places as well. Depending on the indirect method you use—coils or steam jacket—there will also be issues with cleaning and agitation.

Speaking of agitation, there are a couple of different methods you can deploy. The simplest method of agitation is a good ol’ paddle. This typically requires an open-top mash tun that is fairly small so you can reach across the mash tun and touch the bottom. Once you get to 500 gallons or more, you’ll need mechanical agitation in order to access all of the tun and keep things moving. Once you add agitation, a common option is a high shear mixer that will not only break up dough balls that form but can also break up any grain particles that they encounter, helping to decrease grist size in the tun. Of course, a high shear mixer doesn’t help a lot in a lauter tun or if you’re trying to keep your particle size up. The other type of agitation that is useful in lauter tuns specifically are grain rakes and a bottom scraper (to help clean the screen if there is a plug). These tools are mainly only options on lauter tuns, though some combo tuns will still have them when the screen is removed.

We’ve talked about lauter tuns a lot and now is a good time to explain exactly what it is. In its simplest form, it is a screen in the mash tun approximately 6-12 inches above the bottom that keeps a liquid layer below the screen. The idea is that a grain bed will build up on the screen after the majority of starch has been converted to sugar and once the mashing is done. The wort filters through this grain bed, absorbing any sugars that remain attached to the grain particle. Additional water is added and filtered through this bed until all of the sugar is removed from the grain. Some of this water is sent to the fermenter and the amounts with lesser sugars will be reused as the water to start the next mashing. If you are lautering, you will not be able to ferment or distill on the grain.

Fermenters are probably the most overlooked piece of equipment in a distillery because most of the time, when they are working properly, you just ignore them in the corner. They simply do their thing and all you do is fill and empty them when you need to. This unfortunately leads to a large number of distilleries that are fermenting in plastic totes or 55-gallon drums. Although, to be fair, if that’s what you’re intending to do with your spirit, it can work.

The simplest thing a fermenter needs to do is contain the liquid of your wash, wort, or mash while letting the CO2 come out of solution. The easiest way to do this is with open top fermentation and with a vessel that is about 20% larger than your fermentation. This will keep your foam in the fermenter and easily allow the CO2 to get out. Some people object to open fermentation due to the risk of critters and microbes getting into your fermentation and contaminating it, so they add a bug screen or a solid top. If the solid top is added, then typically an airlock is used (a hose into a bucket or a home brew bubbler are the most common) to allow the CO2 to escape. For smaller fermentation, fermentation types that are not temperature sensitive, or rooms that are kept slightly below the desired fermentation temperature, this is typically enough of a fermenter.

Temperature control is typically the first complexity that people like to add to their fermenter. The reason for this is twofold: one is that various yeast strains act differently at different temperatures and the other is consistency. If you want to put extra banana flavor in your rum, you can run your fermentation a little hotter, or if you want to make a rye vodka, then a colder fermentation can help mitigate some of the rye spiciness. When it comes to consistency, if your distillery is 90℉ in the summer and 60℉ in the winter, your fermentations will behave differently depending on the time of the year—both in taking different amounts of time and putting out different flavors. This can be turned into a marketing benefit or you can make different spirits in the winter than in the summer. But for those of you who want to make the same spirit year-round, temperature control on your fermenters is the easiest way.

Most of the yeast used in the distilling industry will rise to the top of the fermenter when they are most active, which then tends to make the top of the fermenter hotter than the bottom. In order to keep the temperature consistent throughout the fermenter, the cooling jacket is broken up into multiple zones with multiple sensors. As that zone gets out of range, it is cooled independently; basically, the top of the fermenter will be cooled more than the bottom. Sometimes an additional zone will be placed in the cone (if you have one), and this zone is kept particularly cold so that yeast that settles down to the bottom at the end of their activity cycle will shut down and not produce off flavors.

Speaking of cones at the bottom of fermenters, that is one of the most common questions: “Do I need a conical bottom or a flat bottom?” And, as with everything else, the answer depends on what you are going to be making. The purpose of the conical bottom is to give solids (dead yeast, molasses solids, or grain solids) a place to settle out so you can minimize the liquid volume they occupy and rack the fermented wash off the top and then clean out the junk. If you are not going to be fermenting solids, except for dead yeast, they really don’t service a purpose because the dead yeast won’t hurt your still or distillation process. Also, if you’re not going to separate the solids from the liquids in your fermenter (either because you’re going to distill on the grain or you’re using a mash separator after your fermenter), then they have no real purpose. Beer is generally done once it comes out of the fermenter so they try to separate out the yeast at that point, but the still works well to separate solids from liquid (actually vapor). So, as long as your solids won’t put off weird flavors when they heat up, you’re ok. Where we see conical bottoms most commonly used is people from the beer world who are doing what they know; people fermenting on the fruit and racking off, also people fermenting on the grain and racking off. It is common for the last two types to clog the conical bottom and have trouble getting the solids out through that two inch opening. In most cases for distilling, a flat bottom (actually slightly sloped) is what you are looking for.

There are a couple of ways to look at stills by how they operate. First off is the question between continuous and batch operation. In continuous operation, the wash or beer is fed into the still continuously while pot ale, hearts and heads come off the other side (there are a couple of different ways for the out products to come off but that’s the most common). Batch operation is the most common in the craft distilling industry because we typically aren’t operating 24 hours a day or even the 16 hours a day where the continuous still becomes more efficient. In batch operations, the still is charged with wash or low wines, or a neutral charge, and then distilled until it is finished. Heads come off the still first, followed by hearts and then tails (again there are some other splits used but this one is pretty common). Once the charge is finished, the still is emptied and then refilled before the next batch begins.

The other way to look at still operation is how it creates reflux—which is what creates the separation between ethanol and water (as well as all of the other chemicals in there). In the simplest case, the wash is heated until the most volatile components are volatilized and then these components are condensed back into liquid in a single step. This operation isn’t really done in modern stills and is practically only seen in those old alchemy set ups with an alembic still. Even in pot stills, there is reflux performed in the head of the still as the vapors expand, cooling down, and the least volatile components turning back into liquid and running down into the pot where they interact with the rising hot vapor. Also, heat is lost through the copper in the head, which contributes to the reflux. Lastly, the height of the head can cause reflux and is one reason for the height of the swan necks in Scotch stills.

While pot stills create ‘natural’ reflux by removing heat from the volatile vapors, other stills cause active reflux. The most common of these professionally is in plated stills, where either a perforated plate or a plate with bubble caps allows for the rising vapor to pass through a liquid leg. In that liquid, heat is exchanged between the vapor and the liquid, causing the vapor to collapse to a liquid and the most volatile components in the liquid leg to volatilize. Basically, this action forces the single distillation above to happen again and again on each plate. There are a couple of other mechanism going on in a plated still but that is the major one. An alternative design to a plated still is a packed column. These are traditionally used either in really large stills (think cracking towers for making gasoline) or the tiniest home rigs. There are some professionals that have upsized their home rigs and some of the less expensive professional stills use them too. By packing the column, you give the rising vapors places to condense and run back down the column to interact with the vapor. Rather than have set plates where this occurs, the interaction occurs throughout the column. There are ways to calculate how many theoretical plates that a packed still has to ensure that you get the separation that you are looking for.

The other type of active reflux involves cooling the top of the still. Historically, this was done with external plates where ice or cold water could be placed. In modern stills, it is done by circulating cold water through a coil or jacket at the top of the still. The nice thing about this design is that the amount of forced reflux can be changed over the course of the distillation and, in some designs, all of the heat can be removed from the vapor, effectively stopping distillation from happening. By controlling your reflux, you can dial a still up to create vodka or have no reflux to make it a pot still. You also have to match the heat input to the cold input in order to use these systems effectively, so they do take a little more experience to run effectively.

When selecting your still, the most important thing to think about is what spirit you want to make. If you are creating a lot of funk in your fermenter using high fermentation temperatures and lots of dunder, then you don’t want that all to be stripped from your spirit by your still, so choosing a design with a high amount of reflux isn’t desirable. On the other hand, sometimes a still with enough reflux that you can jump from your 10% beer to a 60% barrel on a single pass will bring along more flavor than a double-distilled spirit.

There are many different distilling system and generally our advice is to select one that you know makes the kind of spirit you like. If your primary goal is to make American single malt in an Islay style, then we would point you towards a scotch still and make sure you know that your bourbon is going to carry a bit more funk than would be common on a 4 plate American whiskey still. We’ll also remind you that your bourbon being different isn’t a bad thing.

Once you have your finished spirit, you’ll need to prepare it for the market. While assembly lines are still commonly used, exploring ways to automate the bottling process will increase your efficiency. 

There are many good manufacturers, but CRU bottling systems may be a good place to start your search.