Questions & Answers (1)!


We had a successful Drinktec 2022 in Munich. Hundreds of brewers and distillers visited our booth, asked questions, and expressed their interest in our disruptive technology. But what did they ask? What were the questions on their mind, as they saw the iStills? In a series of posts called “Questions & Answers” we will summarize the questions that were asked most as well as our answers.

Question 1

Why are your boilers square instead of round?


Depending on the type of spirit you produce, agitation is needed, so that the boiler contents are well-mixed. In a round boiler the boiler contents will start to move with the agitator system. As the speed differential between the agitator and the boiler contents drops, so does the actual mixing energy that is applied. Therefore, mixing in a round boiler is not very effective and the goal of optimal dispersal of grains or herbs or grapes is not achieved.

As a result, still manufacturers, that do add agitators to round boilers, often have to resort to over-mixing the boiler contents. The now very fast turning agitator throws boiler contents into the gas bed above the liquid bath. This disruption of the gas bed, from which the riser or column harvests its gasses, leads to fluctuations in vapor speeds in that riser or column, hampering flavor consistency and cuts management. Boiler and agitator longevity will be comprised too, as both are over-worked in order to create a higher degree of mixing.

Also, as the boiler contents start to move with the agitator – in a round boiler – a vortex is created. The vortex sucks gasses downwards, competing with the riser or column. This interferes with the riser or column doing its work properly. As with over-agitating the boiler contents, a vortex hampers production speed as well as flavor consistency and cuts management. What essentially happens, in both cases, is that micro burst of over- and under-pressure influence the vapor speeds inside the distillation system, resulting in unwanted smearing of heads and tails flavors into hearts.

The vortex has a secondary negative effect. As the vortex reaches downwards, more boiler contents are pushed upwards, via the sides of the boiler, limiting the fill-grade of that boiler. Especially in combination with over-mixing, this can result in a big difference in gross vs. net boiler capacity. In a round boiler with a gross content of 650 liters, the maximum net filling will be 350 to 400 liters only. The choice for a round boiler severely limits your production capacity, as you have to do more yet smaller runs.

How a square boiler with flush corners helps? Well, first of all the boiler contents cannot start to spin with the agitator. The moment the wash start to move with the agitator, the corners – that are further away – generate a counter rotational movement, keeping the boiler contents in place and thus maximizing the speed differential between agitator and wash. As a result all the energy put in by the agitator translates into actual mixing and perfect particle distribution.

Since no vortex is created – in a flush-square boiler, that is – and no over-mixing needs to take place, the gas bed above the boiler contents is very stable. The riser and column can do their work under optimal conditions, which results in higher production rates, better quality spirits, and recipes that are reproducible from one run to another.

Finally, our 630 liter gross capacity iStill 500 has a net fill rate of 500 liters. That’s about 30% more than an equally sized round boiler. The benefit? You get more still for your buck. You can process bigger batches. Your yield – and therefore your income – is significantly increased.


What reactions did we get, when answering the question of why we have flush-square boilers? The reactions ranged from “that makes total sense” to people being flabbergasted.

At your service!

The iStill Team

Square boilers matter …

Comparing Energy Efficiency: Traditional vs. iStill!


Today, we are diving deeper into the topic of efficiency. As many parts of the world see a rise in energy costs, it is a topic that needs to be addressed. Yes, we all know that iStills are the benchmark, when it comes to efficiency, as they are compact, controlled, and insulated. Traditional stills have outdated designs, that hark back centuries, and are not insulated. But how much is the difference really? Can we quantify it? Put numbers on it? Yes we can and yes we will. Here ya go:

Setting the stage

In one corner, we have the traditional distillery set-up: a 550 gallon masher and stripping still and a 140 gallon finishing still. Both are jacketed and steam-powered. The steam-engine runs on propane.

In the other corner sits the iStill 2000. It is electrically powered and can finish a 2,000 liter batch in one go. No need for double distillation, no need for two stills, no need for a steam-engine.

What will they fight over? New make whiskey. Or whisky. Or Bourbon. The goal is to mash, strip, and finish a total of 4,000 liters or 1,100 gallons of wash into 62.5% new make spirit, that’s ready to hit the barrel. Who will be more efficient and by how much? The traditional set-up or the iStill? And, as a bonus, we’ll also translate energy usage into energy costs.

Traditional efficiency

Based on a real world example by now iStill customer Aris Aristides, that ran a traditional set-up, making American whiskey in the USA, here are his numbers:

  • Mashing 2,000 liters in the 550 gallon masher costs 30 gallons of propane;
  • Two mashes therefore equal an energy use of 60 gallons;
  • Stripping 2,000 liters in the 550 gallon stripping still costs 30 gallons of propane;
  • Two stripping runs therefore equal an energy usage of 60 gallons;
  • The finishing run consumes another 30 gallons of propane;
  • Total propane used is 150 gallons;
  • 150 gallons of propane equals 600 liters of propane (yes, going metric here);
  • One liter of propane provides 7 kWh of energy;
  • So mashing, stripping, and finishing 4,000 liters into new make spirit costs 4,200 kWh.

Aris’ costs when running a traditional, copper set-up …

iStill efficiency

Based on two real world examples, from a French and a Dutch customer, that use the iStill 2000 to make new make spirit in one go, we come to the following energy efficiency numbers:

  • Mashing 2,000 liters in the iStill 2000 costs 150 kWh of electricity;
  • Two mashes, for 4,000 liter total, therefore equal an energy use of 300 kWh of electricity;
  • Distillation run time is 10 hours (including heat-up, based on the latest 54 kWh model);
  • Power usage of 46,5 kW per hour throughout the distillation run;
  • Total power usage, in order to distill a 2,000 liter wash into new make, is 465 kWh;
  • Total power to distill 4,000 liter of wash into new make spirit is 930 kWh;
  • So mashing and distilling 4,000 liters of wash into new make spirit costs 1,230 kWh in total.

The iStill 2000: the craft distiller’s favorite whiskey production machine …


Based on (currently less disrupted) American energy prices, the following can be noted:

  • One gallon of propane costs $ 3.-, so a traditional runs, that use 150 gallons, cost $ 450,-;
  • One kWh costs $ 0.14, so the iStill runs, that use 1,230 kWh, cost $ 172.-

The outcome of the battle?

The iStill 2000 uses 1,230 kWh to mash and distill 4,000 liter. The traditional, indirectly fired, steam-heated, copper set-up used by Aris in his previous, pre-iStill distillery uses the equivalent of 4,200 kWh.

Using an iStill instead of a traditional set-up saves the craft distiller a whopping 2,970 kWh. The iStill is 3.5 times more efficient than the traditional distillery!

Mashing and distilling 4,000 liters results in 440 liters or 2 barrels/barriques of new make spirit at 62.5%. On a traditional, copper set-up it costs $ 450.- to produce this amount. With the iStill the energy bill is just $ 172.-.


If you want to be an energy efficient craft distiller, buy an iStill. If you want to be a cost efficient craft distiller, buy an iStill. If you want to be an environmentally friendly distiller, buy an iStill. And since our customers win more awards than anyone else out there: just buy an iStill.

Why Brewers Buy iStills!


More and more craft brewers buy iStills. Why? Well, the short answer is simply this: because they want to add distilled beverages to their product portfolio.

That’s the short answer. But why do they choose iStill? We spoke to some of our craft brewing customers and here are the top answers they gave.

Process control

“As a brewer, whenever I brew a new style of beer and it is a success, I want to be able to reproduce that beer exactly. That’s why – in the brewery – we invested heavily in process control. Control leads to reproducible outcomes and the same quality beer. What attracted me in iStill is your focus on process control. It allows me to make spirits very much the same way I make beers: in a reproducible manner.”

Stainless steel

“Our brewhouse is stainless steel. It is low maintenance and lasts like forever. That makes it a good material to invest in. iStills were the first stills we saw that were also made from stainless steel. It made total sense for us to choose iStill.”


“When our team wanted to learn about distilling, well, it was as if we ran into a brick wall. Nobody could tell us anything, unless we hired expensive consultants. With iStill you don’t just buy a still. You also become a member of a community where distillers help each other out. Moreover, our experience with the iStill Team and the support they deliver, has been excellent! Very helpful and explanatory”


“In our brewery I took on distilling. What I liked was the education and courses iStill offers. Not only did I make friends for life, also I learned how to distill whiskey, rum, gin, and vodka to perfection. When the iStill arrived I was ready for it.”

Are you a craft brewer interested in distilling?

Reach out to us so we can discuss how we can be of assistance to you realizing your plans!

Releasing Some iStill Rum!

We drew a few bottles of rum from our barrels. Just to see how they are doing. They aged for 2 years and 2 months. Tasty? Very tasty! Already at their prime? No, not yet. We intended to distill this rum in such a way that 4 years of aging would make it perfect. It is pretty darn impressive already. And almost there. All we need to add to it … is a little more patience.

Making Honey Whisky Liqueur, Honey!

Made us some whisky liqueur, last week. Not that difficult. Take a half decent whisky – or if it iStill made: take that amazing whisky – and add honey to it. Heather honey, preferably. Try 250 to 300 grams per liter.

If you make your own whisky, start with higher proof, because the goal would be to reach a liqueur with an alcoholic strength of 40 to 45%. I personally like it at the higher end, but it takes premium ingredients to get you there. When you start out with a very feisty whisky, the alcohol burn might overshadow the sweetness of the honey.

Additions? Well, some orange or even pear extract – made on the iStill Extractor of course – could make a nice addition. But let your creativity run and come up with some personal touches yourselves, please!

It is basically a mix, age, settle-and-rack-off kinda operation. You mix the honey into the whisky. You let it rest for about two months. You then rack-off the clear liquid that sits above a small layer off sediment that comes from the honey. Bottle and enjoy! I like mine served cold, even on the rocks …

Become a Certified Master Distiller Now!

The iStill University organizes a new Certified Master Distiller Training in September. When exactly? From Monday September 5th until Thursday September 8th. Where? In the Netherlands at iStill HQ!

The Certified Master Distiller Training continues where the Certified Craft Distiller Training stops. The first course is mostly theoretical and provides the groundwork of knowledge each and every craft distiller should have. The master distiller course in September is all about training. Training your taste buds. Training you on how to make whiskey, rum, brandy, gin, vodka, and liqueurs. You’ll basically be spending four days behind various stills, making various products, guided by our master distillers. Master distillers that have developed over 450 award winning recipes … and they are at your service!

We still have three places available, due to one customer having to delay their training. Want to learn more about distilling? Want to learn more about the Certified Master Distiller Course? Please reach out to

iStill Whisky Mashing: Grain to Water Proportions!


The iStill is not just a still, it is a complete distillery in itself. The iStills can mash, ferment, and distill. No more need for mashers, fermenters, and/or stripping runs? How’s that for flexibility and ease of use? Quite the game-changer, yes, we know, but that’s not the topic of today’s iStill Blog post. What is? Well, let’s dive deeper into grain to water proportions. How much grain can one dump into the iStill? We’ll use the iStill 2000 as a reference. If you want to translate that to your i500, just divide by four. Do you run an iStill 5000 instead? Multiply the examples underneath by 2.5.

What is your goal?

Mashing is the first step in making spirits. It’s where you break-up starches into fermentable sugars, so that – in the second step of making spirits – yeast can convert those sugars into alcohol.

The more grain you mash-in, the higher the sugar content of the fermentation will be, and the more yield you’ll get. The less grain you mash-in, the lower the sugar content will be. High sugar content washes are best for lighter spirit profiles. Lower sugar content washes result in lower yield but provide higher relative flavor content in the end-product. Lower sugar washes are best for heavier spirit profiles.

Rule of thumb

Here’s an easy to remember rule of thumb: use four liters of water for every kilo of grain. Or, going imperial, 2 pounds of grain per gallon of water. How this translates to the iStill 2000? Use 1600 liter of water and about 400 kilograms of grain. It will get you to about 8% after fermentation.

Beginner protocol

As a beginning distiller, or a distiller working with new (iStill) equipment, we always advise caution. A good start builds confidence. Overcharging or overfilling your still will create a mess, and takes away confidence.

On a first mash, we advise a grain dump of 375 kilos on 1600 liters of water. Use the agitator to the max, dump the grain slowly, and preferably use a hydrator to make sure the grain is wetted before it enters the kettle. Why the lower than 400 kilo grain dump? Because even with imperfect mixing, conversion, etc. you are still well within the threshold of the still’s filling and heating capacity.

What to expect from a 375 kilo grain dump on 1600 liters of water? An SG of 1.069. With a FG of 1.010, this results in a theoretical yield of 7.61%, when fermentation is done. Taking some losses due to CO2 vent-off released alcohol and yeast propagation at the earliest fermentation stage, expect a net yield of 7.1 to 7.2%. Did everything work out okay? Move up a bit and go towards maybe 400 kilo’s of grain on your next run.

Advanced protocol

As you grow experience and confidence, here’s a protocol that pushes it to the limits. 1600 liters of water and 440 kilos of grain. On this mash protocol, you need to use both the agitator to the max, and bring the iStill Mash Pump into play. How? Recirculate the mash via the drain and iStill Pump back into the boiler, while you mix and add more grain. This makes sure that – even at the higher grain dump levels – all grains are dissolved and wetted perfectly. Essential for maximized yield.

What to expect from a 440 kilo grain dump on 1600 liters of water? An SG of 1.081. With a FG of 1.010, the result is a theoretical yield of 9.158%. Considering that yeast propagation – in the early fermentation stages – and CO2 release result in some losses, expect a net yield of 8.5 to 8.6% for your whisky.

Here’s the complete calculation (thanks Richard!)