Cleaning is an essential part of distilling. Keeping a clean distillery isn’t just important to smooth operations, but it’s also important in ensuring proper flavor development in fermentation and distillation, which ultimately carry over into the bottle that goes out to a customer.
Brewers who think distilling demands a lower level of cleanliness than brewing may find themselves in for a surprise. While many (but not all) distilleries require a relatively low level of sanitation in fermentation for flavor purposes, keeping the distillery space and equipment clean remains critical.
The Basics
On a surface level, that means sweeping and mopping in areas such as barrel storage and bottling.
Areas of production, such as mashing, fermentation, and distillation, should be designed and organized with washdown in mind: Can the space be sprayed down and cleaned up conveniently? Will a spill be cumbersome to clean up, or might it leave impossible-to-reach pockets that eventually begin to stink and create a possible source of microbial contamination?
Safety concerns also come into play, particularly with regard to grain handling. Any grain dust that escapes a milling operation needs to be managed diligently; even a thin layer of grain dust on interior distillery surfaces—if it’s thick enough that you can write in it with a fingertip—is a flammable hazard.
In a properly functioning distillery—one that has grain-dust mitigation systems in place, proper fermentation control, and correctly managed distillation—the team is ideally spending more time on cleaning stills, fermentors, or storage tanks than on cleaning floors of spills and rafters of grain dust. Knowing the right chemicals to tap for these jobs—more on those below—can make the difference between an easy task and a painful slog.
Depending on the distillery’s approach to fermentation, the team may clean and sanitize fermentors after every use for a clean, brewery-style fermentation; or they might leave it relatively dirty—perhaps only rinsed of solids between uses. The idea behind that minimalist approach is to accommodate the growth of a “house” yeast and bacterial culture that lends character to the distillery’s fermentation profile.
Even in a facility with a brewery-level approach to cleanliness, the distillers might use a mash tun or cooker repeatedly between cleanings, although it should still be cleaned periodically. Distillation equipment must be cleaned regularly, especially before running finishing distillations.
A still can be used for multiple rounds of stripping between cleanings, depending on the level of caked-on residue that accumulates. Compared to a fermented wash, an on-grain mash leaves more residual solids caked onto the walls or heating element. A high level of scorched or caked-on solids can reduce the efficiency of heat transfer, potentially slowing down distillation.
When running a finishing distillation, that residue can also transfer undesirable flavors to the distillate.
CIP and Specific Products
Most modern distillery equipment—from mash tuns and cookers to fermentors to stills, storage tanks, and even hot- or cold-liquor tanks—are built with or able to be fitted with clean-in-place (CIP) equipment.
CIP equipment generally includes a spray ball inside the tank near the top, through which chemical treatments can be pumped to spray the interior of the vessel with the chemical solution.
A typical CIP cycle starts with a thorough rinse to remove any residual solids, followed by collecting a predetermined volume of water in the vessel. The distiller then adds cleaning chemicals to the water to build the cleaning solution. It’s very important to add the cleaning chemicals to the water, rather than add water to the cleaner. Some powdered chemicals create an exothermic reaction when dissolved; mixing such a chemical with a small amount of water can flash boil, creating a dangerous situation for the distiller.
Once the cleaning solution is ready, the distiller can circulate it in a loop, pulling it out of a port on the bottom of the vessel into a pump, then pumping it up through the CIP ball to spray and break down any soil in the tank. There are also automated CIP systems available that can measure the soil load in the cleaning solution and dump or re-dose the solution with additional cleaner as it’s depleted.
There are a handful of go-to cleaners and sanitizers on the market. For day-to-day cleaning, alkaline chemical agents are the gold standard. These range from the relatively friendly, non-caustic oxidizing alkaline cleaners such as PBW, Bru-R-EZ, and similar formulations available from different suppliers, up to the dangerous and brutally effective caustic soda (sodium hydroxide).
It’s also important to use acid cleaners periodically. Phosphoric or oxalic acid are effective in mitigating beer stone, a calcium buildup that occurs when grain proteins and calcium oxalate react. Facilities that have hard water may require periodic acid treatments to remove scale.
Passivation on stainless steel, via an acid cycle that’s allowed to air-dry and react with the steel, is valuable in removing free iron and maintaining a vessel’s chromium oxide layer that keeps stainless steel stainless.
Running an SIP (sanitize-in-place) cycle on a vessel is similar to a CIP cycle. Just as there are a variety of alkaline cleaners for different needs, a handful of sanitizer options are also available, primarily acidic or iodine-based.
Cleaning regimens and the use of chemical cleaners will vary depending on temperature and concentration, the specific chemicals used, the distiller’s standard procedures, manufacturer’s recommendations, soil load, equipment restrictions, and other factors.
Citric or other acid is also essential for maintaining clean copper inside a still. After CIP-ing the still, the distiller should rinse and then run a mild citric acid solution on any parts of the still that contain copper. This process can be conducted monthly, quarterly, or otherwise, based on the usage of the still. Over time, the copper surface of the still binds with sulfur and other compounds during distillation, and occasionally it’s necessary to strip off the microscopic, outermost layer of copper, leaving behind fresh copper to react with the distillate.
Besides for interior cleaning, you can use citric and other acids to manually clean the exterior copper on a still. This is a cosmetic choice based on the distillery’s aesthetic: Some distillers prefer a bright, new-copper finish on their still, while others embrace the well-used feel of patina.
Elbow Grease, and Other Tips
Chemical applications are often adequate for standard cleaning tasks, but every distiller, at some point, needs to roll up the sleeves and do some scrubbing.
In those cases, it’s important to select implements that won’t mar a tank’s surface; overly aggressive scouring pads can create scratches in the stainless steel, creating microscopic spaces where bacteria and residues can gain a foothold. The tank may wind up clean in the short term, but it will be more prone to contamination in the future. For more about practices to observe and avoid when scrubbing stainless, see “How to Protect (or Ruin) Your Distillery’s Stainless Steel,” spiritsanddistilling.com.
Along with manual applications such as brushes and scour pads, a pressure washer can be a valuable tool. It may be the initial step in cleaning, or the final step—knocking off soil that’s been softened by a chemical CIP—or both, when dealing with thick, caked-on residue. It may be helpful to alternate between a using a chemical to soften and loosen the soil, then a power washer to remove the topmost layer, switching back and forth as needed.
Process parts in the distillery—items such as clamps and gaskets, valves, racking canes, and other items that may not get cleaned in a standard CIP—should be soaked in a mild, non-caustic cleaner and scrubbed after use.
Cleaning is an essential task in any distillery. Good cleaning practices precede a successful distillation; building, blending, or proofing product in a tank; and other processes.
It lays the groundwork for repeatability, proper flavor development, and efficient distillery operations, so it should never be overlooked.