What Is A Thumper Keg (And How Do They Work?)

Nothing beats a beautifully flavored and smooth final spirit. If you want to avoid multiple distillation runs while ensuring that you get high-proof alcohol without impurities, a thumper (or thumper keg) is a tool worth investing in. In this article, we’ll discuss what a thumper keg is, why you need one, and how it works. Ready? Let’s go!

What Is A Thumper Keg?

A thumper keg is a container used as a location for secondary distillation. The container is made from heat-resistant materials such as glass, copper, stainless steel, or wood. The thumper is connected to the still typically using copper pipes and placed between the still and the condenser. 

Alcohol vapor from the main still passes through a copper pipe and bubbles through the liquid in the bottom of the thumper. You’ll often hear thumping sounds when the still is operating when this occurs, hence the name. Thumper kegs give your final spirit a high alcohol content and enhance the flavor of the alcohol in it.

A Brief History Of The Thumper

Thumper kegs are believed to have been invented by European colonists. When they came to settle in North America -before the American revolution- they brought the thumpers along with them and assembled them into the stills. They used the thumper as a secondary distillery. 

During the Prohibition era, moonshiners found the thumper significant in controlling heat and producing a high alcohol content in the final product. From then on, home and commercial distillers adopted the use of thumpers when making spirits.

How Does A Thumper Work?

A thumper works by distilling the low wines from the still. When hot ethanol vapor moves from the still, it goes into the thumper and turns to liquid. Then it heats the low wines and allows a second distillation to happen.  Instead of heating the thumper as you would the still, it uses the heat waste carried in the low wines. The low wine in the thumper vaporizes and the vapor is carried through the copper pipes, into the condenser, and into a collecting jar.

Do You Need A Thumper?

Yes and no. Without a thumper, you’ll need to go through multiple distillery processes to achieve high alcohol levels. But, using a thumper has the following advantages:

  • You can better control the heat. Because there’s (typically) no heat source under the thumper, the liquid has a better chance of cooling off before heating up during the thumping process.
  • You go through the second distillation in one go. As mentioned earlier, a thumper acts as a secondary distiller. So you won’t have to use multiple stills to achieve high alcohol levels. 
  • You can use it as a gin basket. If you love adding flavor to your spirit, a thumper allows you to do that. You can add fruit and botanicals at the bottom of your thumper. The vapor will extract flavors coming out of the thumper into the condenser.

But, if you want to skip the thumping process, there are some alternatives you can consider. 

What’s The Alternative To A Thumper? 

While a thumper is effective at distilling spirits without the hassle of moving your spirit from one still to the next, a reflux column still can effectively distill your alcohol. Most reflux stills include copper meshes. The copper mesh removes any impurities from your mash. Also, with a reflux still, you can create up to 95% alcohol content. The only downside to using a reflux still is that it strips too much flavor from the distillate.

How To Add Flavor With A Thumper

Pouring fruit or herbs into your thumper is a fantastic way of adding flavor to your spirit. Before distilling, pour some mash or alcohol from your previous run. Adding alcohol increases the alcohol percentage in your final product. You can also use water, but water is added as a last resort because it can affect the alcohol percentage (you’ll get low alcohol content) of your drink. Once you’ve added the alcohol, you can use one of the following methods to add flavor:

Add fruit, herbs, or spices. 

Take any fruit, herbs, and spices of your choice, place them in a container, and cover them with low wines. Let this sit for a week or two. When ready to distill, add the mixture to the bottom of your keg. As the vapor moves from the keg, it will take the flavors with it.

Raw fruit

You can also take ripe, mashed fruit and add it to your keg. For this method, you’ll need to add more fruit, herbs, and spices to your thumper.

Pour juice

If you don’t have time to wait for the fruit to break down and infuse with low wines, you can add juice to your thumper instead. Take the fruit juice of your choice and add it to the thumper.

How To Use A Thumper Keg (Step-By-Step Instructions)

If you’re using your keg for the first time, you’ll need to clean your thumper keg to remove any bacteria that might contaminate your still. You can clean your thumper using a vinegar solution (also called a vinegar run). Follow these steps to make a vinegar run.

How to clean your thumper keg.

  1. Mix half vinegar with half distilled hot water and pour it into your boiler. Ensure your boiler is filled up to 20% capacity. 
  2. Distill the solution from your boiler into your thumper. 
  3. Wait for the temperature on the still to reach 172 degrees Fahrenheit (78 degrees Celcius), and keep the heat source on for 5 minutes.
  4. Turn off the heat source, and allow the equipment to cool down.
  5. Discard any vinegar solution. Now you’re ready to use your thumper keg.

How To Use The Thumper Keg

  1. Assemble your pot still to your keg and condenser.
  2. Pour the mash into your still.
  3. Add some alcohol to the bottom of your thumper. The alcohol can be mash or spirits from your previous run. If you wish to add flavor to your spirit, add your fruit, spices, and herbs at the bottom of your thumper.
  4. Heat up your still to about 172 degrees Fahrenheit (78 degrees Celcius).
  5. Ethanol vapors will pass through the copper pipes into the keg. As the vapor goes into the thumper, it will turn into liquid. 
  6. Allow the thumper to run and collect your distillate into glass jars.
  7. Once the thumping process is over, turn off your heat source. 

CAUTION: When you turn off the heat source you’re most likely to cause back pressure. This can potentially lead to an explosion and crush your still. So to mitigate this, unscrew the pipes where they join between the thumper keg and still as soon as you turn off the heat source. Use gloves to unscrew the tubes to avoid burning your hands. 

Frequently Asked Questions:

What size thumper do I need? 

You need ⅓ the size of your still. That’s about 20% to 40% the size of your still.

What liquid should I put at the bottom of my thumper?

You can add wash or the spirit from your previous run at the bottom of your thumper. Alcohol increases the alcohol percentage and enhances the flavor of your final drink. You can also add water, but you’ll end up with low-proof alcohol if you choose this option.

How much liquid do I use in my thumper?

You should use not more than ⅔ of liquid in your thumper. This allows enough pressure for the vapors to move from the thumper pipe to the condenser.

Conclusion

Thumper kegs are a practical tool for brewers of all levels. If you’re looking to improve your distillation process and the alcohol content of your drink, thumpers are worth having. Have fun with your keg and flavor your spirit whichever way you feel you’ll enjoy it best.

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