Dipping a toe into the deep well that is water’s role in the process of distillation, including mashing, reduction, and cooling.
When writing about alcohol, we tend to focus on just that, but it’s far from the only substance present in the glass. It might seem odd at first to look at something as ubiquitous as water and discuss it outside of the context of a scientific paper, but water is involved in each step of the distilling process, from mashing to cooling to reduction, and it can often be a source of unresolved consternation for distillers. It has an immense effect on the flavor and clarity of a spirit, and some believe water to be a distinct source of terroir.
The kind of water that you use for mashing is significant, but distilling fine spirits is about more than having good water. Using bad water, however, is an easy way to derail the productive steps you’ve otherwise made. So what does good water mean?
Where It Comes From
As we all learned in elementary school lessons on the water cycle, water starts as pure H₂O in a gaseous or vapor form up in the clouds. As H₂O condenses to form droplets of water, it reaches out to absorb other gases from the air, like carbon dioxide, as well as dust particles and any tiny mineral crystals it can find. These substances aid in the condensation of water droplets but they also contaminate the water (Palmer & Kaminski, 2013). After precipitation, rain and snow collect on the ground to become surface water. The longer the water remains in contact with the earth’s surface, the more dissolved or suspended substances will be found in it, substances like plant or animal-based organic matter, or other compounds such as herbicides and pesticides. Sodium chloride, calcium sulfate, and other minerals will also find their way into the water (Palmer & Kaminski, 2013).
But surface water doesn’t stay there; eventually it seeps into the ground, and during this process most of the organic matter is filtered out and the water becomes exposed to even more minerals. Groundwater can reside in aquifers for hundreds or even thousands of years, during which time further minerals dissolve into it. Areas with carbonate soil and rock formations often lead to the surface water’s ability to achieve higher hardness and alkalinity concentrations. It is eventually brought above ground by springs, wells, and seepage into rivers.
There are three primary sources of fresh water: precipitation, surface water, and groundwater. Distillers and brewers often highlight their water source in the marketing material for their product, or even name their distillery after it, and there are pluses and minuses inherent to each source. Recent rainfall or snowpack precipitation tends to have a lower pH than surface water and very little organic matter. Surface water from rivers or lakes is more likely to be contaminated with organics, such as debris or plankton, and it will have “a moderate concentration of dissolved minerals and alkalinity” (Palmer & Kaminski, 2013).
Water used for mashing or brewing has to be clean, and it should be of low alkalinity (preferably of CaCO3 at 50 ppm or less, but no more than 100 ppm) so that a distiller can target the pH of the enzymes and create a healthy fermentation. Some water that is safe to drink is still not clean enough for brewing because it can contain chlorine, chloramines, dissolved gases, or organic compounds that can affect the flavor of your wash. It’s advised that you taste your water before and after each step of distillation to ensure it is still suitable.
The alkalinity of suitably potable water can be adjusted by acidification — lactic, sulfuric, or phosphoric acid are common methods. If your water source can be adjusted, aim for a calcium ion level between 40-70 ppm, which will provide the proper amount of nutrients for the yeast during fermentation. Distillers might use local untreated surface, well, or tap water, believing that the mineral content is of little significance, but sufficient levels of minerals are needed by yeast for a healthy and efficient fermentation.
Water pH is important for a distiller to know, but knowing what the pH of your water is without understanding the composition of the water will not aid you in predicting the pH response of the mash. Minerals in water have a significant effect on the process of mashing because they include a buffer system, meaning that there is a substance in the solution of the mash that resists changes in pH. Change in pH will be resisted more if the buffer is stronger. (Most enzymes activate best at a pH between 4.8 and 6.) Alkalinity acts as a buffer in potable water via the carbonic, bicarbonate, and carbonate equilibrium. Phosphate, another buffer, comes from the mash, and it is the interaction between these two systems and calcium and magnesium that determines the steps you will need to take to change the pH of your mash.
Ultimately, it’s your mash pH that you want to pay attention to, but it’s important to know the pH of your water to find out how it’ll affect the mash. The mash pH is at once the result of a reaction between the water and malts and a factor in that reaction. If pH is the result of chemical equilibrium, your mash pH is something that you can control to improve the performance of the mash, i.e. ensure optimum enzyme activity and favorable conditions, while simultaneously being the result of that chemical reaction. Thus, the point during the process of brewing that is key for pH control is during mashing because great influence can be applied at this stage on the buffer systems, mentioned above, which will affect the wort and final product (Palmer & Kaminski, 2013).
Kentucky bourbon is a great lens with which to consider the question of water’s effect on spirits. The geology of Kentucky’s Inner Bluegrass region is defined by underlying Lexington limestone, which dates back to the Paleozoic era. The majority of this region is drained by the Kentucky River and tributaries that flow off it. Any mention of Kentucky bourbon is usually followed up with something about the limestone water responsible for its excellent flavor. Limestone water, or “hard water” as it’s known to most outside the distilling industry, flows through the limestone or chalk that is part of the Inner Bluegrass region. As it does so, minerals like magnesium and calcium are deposited into the water from the surrounding limestone, and it helps to remove innate iron in the groundwater naturally. The nutrients — calcium and magnesium — are crucial for the yeast to thrive during fermentation.
“[Distilleries in Kentucky] don’t tell you that they use purified water to dilute down the spirit at the end of the day,” said Gary Spedding, Ph.D and managing owner at Brewing & Distilling Analytical Services. Limestone water is great for mashing, but purified water is the standard for reduction or dilution of a spirit before bottling. There is really no wiggle room here; water must be purified, either by reverse osmosis (RO) or deionization, and all minerals and organic materials must be removed to avoid any unwanted turbidity (precipitates or haze) in the final bottle or any unintended effects on taste. At this point, the introduction of calcium would cause calcium oxalate precipitation in the bottle. “A fellow from Brown Forman was the one that told me that as little as two ppm of calcium in the final product can cause precipitation,” continued Spedding. Magnesium ions are also among the usual suspects in haze precipitation, and any leftover iron will cause your whiskey to turn black and bitter.
Spedding wrote about colloidal stability, which can be an issue for either clear or aged spirits, in a piece for Artisan Spirit Magazine. “A colloid is a homogeneous, non-crystalline substance consisting of large molecules or ultramicroscopic finely divided particles (1 to 1000 millimicrons [10-9 meter or nanometers] in size) of one substance dispersed within a continuous medium in a manner that prevents them from being filtered easily or settled rapidly” (Spedding, 2017). Haze is the result of these colloids being scattered lightly throughout the spirit, where they are suspended in the solution. Clear spirits are stored in stainless steel containers that must be free of any other minerals as they can lead to clouding.
“The other thing that you have to watch for with precipitation in bourbon is a compound called β-sitosterol, and that is the main reason that they do chill-proofing,” said Spedding, referring to the chill filtration employed by many of the big bourbon and scotch brands around the world. “It’s another fatty acid complex, so we don’t know whether that might interact with metals and come out of solution, but β-sitosterol is one that comes out of the wood, from the wood chemistry, so you’re not usually going to see that in a naked spirit, it’s only [in] a mature spirit. So you’ve got that issue and then you’ve got the potential mineraline issues to deal with.” While minerals and β-sitosterol are some of the traditional sources of floc and precipitates, there are also new issues to contend with. As more producers enter the distilling industry, so have more glass suppliers, and some bottles that have come into the American market have done so with unintended consequences. “It turns out they’re getting bottles from China, and what they will normally do is they will spray — and it’s supposed to be a food grade oil, like olive oil [but] not necessarily olive oil — they’re supposed to spray that on the outside of the bottles to prevent scuffing during transport and even bottling, but sometimes we think that spray is getting inside the bottle,” said Spedding. This has led to unusual precipitates, some of which are able to go back into solution.
Though not nefarious on its own, these floating particles can be visually displeasing and a deterrent to potential customers. This phenomenon of unidentified floc is concentrated on the craft side of the industry; part of the reason for which is the water source. Many craft distillers highlight their water source in the marketing for their product, which can be a great way to connect to the local community but can become problematic if said water source is creating floc in the spirit. If a distillery is unwilling to rethink their source of water, Spedding mentioned other solutions. “Stick a label on saying this product is likely to cause a light sediment over time. It’s innocuous, just ignore it.”
While not as functionally important as the water selected for reduction, the water that a distiller uses for cooling should be considered with great care as it can affect the physical aspects of the distillery. Some suggest using low solids water as it prevents mineral build up in lines or vessels such as steam jackets. Public works water that is suitably treated is usually fine for this purpose, though obviously it should not come in contact with the spirit at any time. Distilled water should never be used for cooling down; pure water is hungry for ions and can remove electrons from the cooling system metals chemically, leading to extreme damage.
Water is a key element to consider when making any spirit. If you aren’t fortunate enough to have a scientist on your team, consider consulting with one before you become married to the idea of using a certain water source.
Palmer, J. & Kaminski, C. (2013). Water: A Comprehensive Guide for Brewers. Boulder, CO: Brewers Publications.