When the Heising family purchased a batch still and installed it in a distinctive structure they dubbed “The Bunker,” which is built into a hillside on an island in Washington’s Puget Sound, it was the beginning of Whidbey Island Distillery. But when it turned out that the success of their business hinged on the creation of a different type of still, which is typically used in large-scale industrial processes, they decided that they’d better figure out how to build it themselves. And not only did they succeed in building it, they used it to produce a blackberry liqueur that’s currently the highest rated spirit in North America according to the Beverage Testing Institute.

Jim Heising, who started Whidbey Island Distillery with parents Bev and Steve, describes some of the initial challenges their business faced. “Distilling might be fun as a hobby, but months straight, of long hours of watching the still turned the fun into grueling work.” Heising explains how issues that wouldn’t be a problem for a hobbyist became serious hurdles for their business, like regulating the output of the spirits they made from wine with their batch still. “Our source of wine was always changing; every run behaved differently and needed to be closely monitored and controlled.” And in order to sustain their business, Whidbey Island Distillery had to make sure that their customers would be able to count on a reliable product. “Creating a consistent flavor profile was like trying to make money by predicting the stock market. Distilling, re-distilling, and blending required keeping and logging numerous containers. This created a paperwork nightmare,” says Heising.

It didn’t take long for Heising to realize that he needed to rethink their production process. “I simply could not produce enough alcohol that I was happy with. I had to find an alternative. I considered buying a larger still, but I determined that even if I bought the biggest and best vodka still I could afford, it wouldn’t make our product significantly more affordable, and I would still be a slave to it.”

According to Heising, there are two types of stills that are generally used in distilleries; batch stills, and continuous stills. “Most small distilleries use batch stills because continuous stills typically cost millions of dollars to build, run, and maintain— think oil refineries.” But for Whidbey Island Distillery to create a product with which they were satisfied, and that worked with their business model, Heising decided that he would simply have to build a small continuous still himself. And because he didn’t actually know how to build a small continuous still, Heising resolved to put his maker boots on and learn as he went. “Because distilling is illegal without the proper licenses, it’s not exactly easy to find people to collaborate with— especially when you’re building something completely new. So you might argue that distilling is the perfect embodiment of the bootstrap maker culture.”

Whidbey Island Distillery’s two continuous stills at work in “The Bunker.”

As every good moonshiner knows, the process of distilling ethanol (the stuff that gets us drunk!) consists of three basic outputs: the heads, the hearts, and the tails. The output is divided into these categories because the overall output can contain potentially dangerous levels of compounds other than ethanol, including methanol, which can cause blindness.

The concentration of various compounds changes throughout the distillation process because they evaporate at different temperatures. In a typical batch still process, the heads, which is the first output collected, will have the highest concentrations of dangerous or undesirable compounds. The hearts is the second output and has the highest concentration of ethanol. The tails is last, it often has lower concentrations of ethanol and some other impurities. This means that the hearts is sometimes the only output that’s kept, but Heising explains that things can get complicated depending on the desired result. “The challenge to any distillation process is that there is not a clear line that delineates any of these different compounds— there is *always* a small amount of every compound in every drop that comes out of any still. The trick and art of any distillation method is to make sure that the majority of the molecules you pull out are the ones you want. And ‘the ones you want’ is defined entirely by your taste and discretion as a distiller.”

Batch stills have to be carefully monitored to ensure that the heads, the hearts, and the tails are separated out at the right stages in the process. “You might think of batch distilling like waking up every morning to bake individual loaves of bread in your kitchen. It’s a serial process where you can’t get to point C without going through A and B first,” says Heising. “A continuous still on the other hand is a parallel distillation process that can run consistently for an indefinite amount of time— you can still formulate your unique bread recipe, but when you walk away, it will keep making that same great bread until you stop feeding it ingredients.” This eliminates the need for a continuous still to be attended to throughout the process. “The [continuous] still is capable of running continuously and unattended for months on end which results in a huge savings in labor costs as well as major gains in consistency,” says Heising.

So, how is a continuous still able go through the entire distillation process simultaneously? “The still works by maintaining a precise temperature gradient from near the boiling point of water at the bottom, to around 140F at the top. At three specific points in the column, there are what we call “draws”— where we condense the alcohol vapor back to liquid and alternate between collecting it and sending it back into the column for additional refining (called reflux). These draws are at specific points where the temperature in the column is near the boiling point of the specific chemical we want to remove from the still. We can also control these temperature points in the still with various other proprietary mechanisms,” explains Heising.

Not only does the continuous still Heising built produce the desired results, it produces them on a scale that could only be possible with a customized still. “Our still is unique because it is a continuous still that doesn’t cost millions of dollars to build and maintain. You might say we took the process of an entire factory and shrunk it down to something that would fit in your closet.”

In a 2014 talk that Heising gave at Cascadia JS, a community-driven conference on cutting edge JavaScript, he described how writing code played a critical role in the development of his continuous still, using a board level Linux computer with a custom built circuit board to control over 10 digital sensors, power controllers, pumps. It even has a barometer, which suggests just how complicated the whole process is. “We’ve got a barometer on this thing because the boiling point of liquids changes with atmospheric pressure, so we actually have to take that into account,” says Heising. Without the code Heising wrote to control and constantly monitor the still, it would need a lot of supervision, but instead it’s able to run on its own. “It takes care of basically all of the housekeeping in an industrial process,” says Heising. And, even though the still is designed to run on its own for long periods of time, it’s also connected to the internet so that it can be monitored and controlled remotely.

Whidbey Island Distillery now uses two continuous stills; one for liqueurs (Still2), and one for rye whiskey (Still3). “We wanted to make a proper rye whiskey (not a light whiskey), but that meant we needed to distill it at 160 proof or under. But if a distillate is 160 proof, or under, it has to contain a lot of water. There are simply not enough other alcohols or congeners in a fermented wash to lower the proof to 160 without having water in it. So we had to modify the physical configuration of Still3 to distill some water along with the alcohol. Still3 gave us experience in tuning the distillation parameters to select the flavor profile that we liked best.”

After having successfully built a number of stills, Heising started Bunker Stills, his own brand of continuous stills. And Heising says his stills have changed over time as he has modified his designs and used various electronics to monitor their function. “The latest generation of the still is powered by an off-the-shelf Raspberry Pi 3. The original stills were first powered by an Arduino and replaced by a Linux computer called the pcDuino. Another example of using more modern off-the-shelf technology is our use of DS18B20 1wire digital temperature sensors. RTD probes are typically the standard in industrial automation, but they require a separate connector and ADC for each probe. We wanted to be able to quickly and easily instrument any part of the still with a temperature probe at any time and didn’t want to have to add a new connector and ADC each time. So the 1wire protocol was perfect for us— we could add virtually as many probes as we wanted and use the same 3 wires for all of them.”

Creating the highest rated spirit in North America is an impressive achievement in itself, but making it by building a computer-controlled still from scratch is truly extraordinary. Although, Heising admits his success was not due to his skill and experience alone, it was his ambition that really made the difference. “Perhaps the most important thing we learned along the way is that you need to be determined to make it work despite what the books and experts tell you.”