Pot Still Puking (Why Is My Still Boiling Over?)

Image of diy distilling why is my still puking and how to fix boilover

As a new distiller, one of the most dampening feelings is winding up with a puking still. Even more so, when you’ve excitedly set up your still and have it running and had it run for the whole run. So, what exactly caused it to boil over?

A few common causes of a still boilover are increased heat, an overloaded boiler, and an unfermented wash. Heat causes a lot of turbulence resulting in air bubbles cascading, resulting in foam. If this foam does not get controlled, it boils over in your column or Lyne arm as a way to control excess liquid in the still.

Carry on reading this post to find out the causes of a puking still and how to avoid it.

Why Is My Still Puking?

Boiling over is not fun. It’s messy, and if it happens during a spirit run, it can be disheartening because it’s a waste of good wash. Here’s an explanation of what happens inside your still to cause puking. 

First, What Is Puking?

When a still charge foams up excessively, the wash in a pot or reflux still boils over from the column or lyne arm into the condenser and into your collecting jars. If your moonshine has a red, orange, or brown appearance with some foam to it, then it’s a case of puke.

Some products have a high starch content – molasses, potato, and all grain-based, so they tend to foam more than other bases.

Image of diy distilling image of pot still boiling over

What Causes A Still To Puke?

Some common reasons behind a puking still include.

  • Too high a temperature. This creates excess vapor flow. The increased flow of vapor forces liquid out of the column to relieve the vapor pressure. 
  • Limited headroom. Limited space for the foam to collapse back to the boiler prevents the vapor from developing and moving up the column.
  • Unfermented wash. An unfermented wash has CO2 available. When combined with the starchy ingredients in the wash, it creates air bubbles which ultimately form foam. When the gas comes in contact with heat, it starts off-gassing, therefore it erupts.
Image of diy distilling sightglass in distillation column showing that still is puking or boiling over

How To Tell If Your Still Has Puked 

When the distillate exiting the condenser turns out black (molasses-based) or when the distillate turns out red, brown, or yellow, then that’s an effective way to tell that you still has puked.

What To Do If Your Still Has Puked:

The best thing to do when your still puked, it’s best to turn off the heat and clean up the mess. If performing a stripping run, you can add this to the boiler for a spirit run. 

5 Tips To Stop Your Still Boiling Over (How To Avoid Puking)

Here’s our top 5 tips to avoid puking.

Note: some of these like turning the heat down you can do mid run. Others, Like adding agents to the boiler you’ll need to do before you fire up your still.

1. Fill the boiler less 

Filling the boiler less makes for increased headspace. This means any vapors that might turn to foam will have enough room to break down the air bubbles, liquefy and collapse to the bottom of the still.


  • Less chance of puking.
  • Controlled foam control.


  • Time-consuming, and will require you to perform multiple stripping runs. 

2. Lower the heat 

The higher the heat, the likelihood of foam formation. By decreasing the heat, it means the wash won’t have a chance to boil over.


  • Less chance of the wash boiling over.


  • The process of adjusting the heat can be time-consuming. It means instead of completing your stripping run in approximately 12 hours, it can take you more than that.

3. Use an anti-foaming agent 

Adding an anti-foaming agent reduces the surface tension of the wash. This is because most agents have a low surface area. That allows them to spread evenly across the wash, penetrate and pop the air bubble’s film-lamella.

Doing so prevents the chances of air bubbles joining and forming foam.

Most commercial antifoaming agents are silicone-based. Silicone is insoluble in water and has the desired surface area to knock down air bubbles. The properties found in this compound are preferred because it means distillers and brewers can use it in small doses, which offers value for money.

Read More: This article discusses the best anit-foaming agents for distilling.


  • Highly effective at reducing foam when distilling.
  • Most agents don’t have the potential of imparting flavor to your wash. 
  • A little goes a long way. A single drop can effectively pacify foam-forming ingredients in your entire wash.


  • If using powdered form agents, they might leave a bitter taste on your final spirit. This is because it binds to the yeast before it breaks down the film and protein

4. Add some linseed oil 

As the saying goes: oil doesn’t mix with water. This is because oil is insoluble in water, so what it does in the case of a wash, instead of binding to the compounds and liquid, it pops the air bubbles and prevents them from sticking together.


  • A natural and effective substitute for commercial anti-agents.


  • If used in high doses, the taste can carry over to your final drink. 

5. Pre-boil your wash 

The act of pre-boiling your wash releases the gas and allows it to precipitate. This also effectively breaks down protein.


  • It breaks down foam-forming starches and protein.


  • May kill some enzymes responsible for fermenting your wash.


Fortunately, having a puking still is a mishap that can be prevented. Boilover is mainly caused by the heat causing air bubbles that eventually cascade and foam. There are ways to reduce foam formation. You can pour just enough wash in your boiler to leave enough head space for the foam to collapse before it boils over. Alternatively, you can use an anti-foaming agent to tame the gas, starch, and protein found in your wash. Pre-boiling your wash is also another great option, provided you have some enzymes handy to make up for any denatured enzymes in your wort. 

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