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What Are They?
How do They Work?
by NorCal Brewing Solutions
There is nothing worse than spirits that are harsh, throat burning, off flavored, or have odors or impurities.
Common distilling wisdom dictates that to avoid the above you should perform multiple distilling runs.
But who’s got time for that?
If you don’t… add a thumper (also known as a thumper keg) – or even a series of thumper kegs – to your pot head distilling system!
What Is a Thumper Keg? (Short Answer)
A thumper keg is a sealed, liquid-holding container that is placed between the still and the condenser in a pot head distillation system.
It has one ethanol vapor entry port and one ethanol vapor exit port.
It essentially performs a secondary distillation during a single distillation run.
A thumper keg enhances alcohol content while simultaneously refining the flavor of the product – whether it be gin, whiskey, rum, or anything else.
How Does a Thumper Keg Work?
Hot ethanol vapor passes from the main still into the thumper through a DOWNCOMER – a tube whose end is submerged in “Thumper Liquid” at the bottom of the thumper.
It is preferrable to have the Thumper Liquid be related to the spirit being distilled.
For example, the Thumper Liquid can be:
· Mash from the current run
· Collection from a prior run
· Store-bought spirit of similar type
· The Thumper Liquid can contain fruit, spices, botanicals, or juice to enhance the flavor (more on this later!)
· Water can be used as a last resort. Using water will substantially dilute the alcohol content of the collected spirit.
The hot ethanol vapor bubbles through the Thumper Liquid, cools, and in turn becomes liquid itself, mixing with the Thumper Liquid already in the thumper.
As the vapor condenses in the semi-sealed environment it produces a THUMP – THUMP – THUMP sound, from which the name “Thumper” is derived.
The collected spirit has a high alcohol content and enhances the flavor of the spirit.
CAUTION: Due to a thumper’s proximity to the still it will get hot!
For this reason, the thumper keg container should be made from heat-resistant materials (stainless steel, copper, glass, etc.)
NorCal Brewing Solutions manufactures a line of thumpers designed for 1/6 barrel Sanke kegs and an economical line for glass canning jars (Kerr, Mason, and Ball).
Let’s Get Technical!
Okay… but how does this produce a SECONDARY DISTILLATION?
A thumper works by distilling low wines that come from the still.
When distillation first starts, the starting liquid in the thumper keg is cool.
As hot ethanol vapor passes from the still through the thumper the heat waste carried in the low wines heat the thumper up.
NOTE: Typically, no other heat source is used. This allows greater temperature control should the mash temperature get too hot.
Eventually, the low wine gets heated to a point where it vaporizes, a second distillation happens, and this newly distilled vapor passes out of the thumper and into the condenser (or… into ANOTHER thumper keg).
The final spirit exits the condenser and is collected.
In essence, a thumper keg allows a pot head still to gain some of the features provided in the column portion of a column still.
Can a Thumper Keg be Used with a Column Still?
The short answer is “no”. There simply isn’t enough energy left to run the “thump” by the time ethanol vapor leaves a column still.
A Thumper as a Gin Basket!
A thumper keg can be used to add flavor to spirits.
Simply add botanicals, herbs, spices, fruit, juice, or extracts to the Thumper Liquid and the ethanol vapor will extract the flavors from the Thumper Liquid as it passes through the thumper and exits into the condenser.
What Size of Thumper Do I Need?
A thumper should be approximately 1/3 the size of the still.
So… 1/6 barrel kegs are PERFECT as thumpers when used with a half barrel (15.5 gallon) Sanke keg still.
Half gallon canning jars are PERFECT as thumpers for 1.5-gallon stills.
And don’t forget…
Thumper Kegs can be used in series to double thumper capacity, triple it, and so on.
Two NorCal Brewing Solutions Half Gallon
Canning Jar Thumper Kegs used in Series
First Time Thumper Set-up (Step-by-Step Instructions)
The thumper keg must be cleaned to remove bacteria and other contaminants. An easy way to accomplish this is through a “Vinegar Run”:
NOTE: If using a series of thumpers, perform a Vinegar Run on each thumper individually (don’t assemble them in series).
1) Determine what 20% of the still’s capacity is. (1/6 barrel keg would be 20% of 5.17 gallons = 1.03 gallons). This is the “Vinegar Run Volume”.
2) Assemble the still, thumper, and condenser.
3) Mix half distilled water and half vinegar to make up the Vinegar Run Volume. Pour into the still boiler.
4) Start distillation by heating boiler.
5) Apply heat until distillation vapor temperature reaches 172 degrees Fahrenheit (78 C), hold this temperature for 5 minutes. This should allow the thumper to have collected vinegar.
6) Turn off heat source. Allow all equipment to cool down.
7) Discard all solution from still and from thumper.
8) Thumper is now ready for use.
Using a Thumper Set-up (Step-by-Step Instructions)
1) Assemble the still, thumper(s), and condenser.
2) Add mash to still boiler.
3) Add enough Thumper Liquid to the thumper to cover approximately half an inch of the bottom of the downcomer.
4) If using the thumper as a Gin Basket: Add flavorings to the Thumper Liquid.
a. Make sure thumper keg is no more than 2/3 filled with Thumper Liquid and any additives. More than 2/3 full could produce too much back pressure for the thumper to work properly.
5) Heat boiler of the still to approximately 172 degrees Fahrenheit (78 degrees Celsius).
6) As the still heats up, ethanol vapors pass through the still and into the thumper (through the downcomer), where the vapors will turn into liquid and mix with the Thumper Liquid.
7) Eventually the thumper will heat up enough where ethanol vapor will continue out the thumper’s exit port and through the condenser, where it will turn into the final collected spirit.
8) Once the thumping process is complete, turn off the heat source to the boiler.
WARNING: Understand and ALWAYS follow proper still shut-down procedures. Failure to shut down the distilling process correctly can cause back pressure, resulting in equipment damage and even an explosion!
Adding Flavor by Using a Thumper Keg
A thumper can replicate a Gin Basket by adding flavor(s) to distillate!
Simply add fruits, fruit juice, herbs, extracts, flowers, or spices to the Thumper Liquid.
NOTE: Using anything but alcohol in the Thumper Liquid will dilute the alcohol content of the collected spirit. If high alcohol content is a priority, consider using multiple thumpers in series.
Adding Dried Fruit, Herbs, Flowers, Spices:
Use any combination of dried fruit, herbs, flowers, spices, etc. and place them in a container. Add enough low wines to cover completely. Cover and let sit for 2 weeks or until contents break down and get infused with low wines.
When ready to distill, add this mixture to the Thumper Liquid.
Pros and cons of this method:
PROS: Allows good flavor extraction while keeping the highest possible alcohol content of the collected spirit.
CONS: Time delay / hassle.
Adding Raw Fruit, Fruit Juice:
Use any combination of ripe, mashed fruit and fruit juice and add it to the Thumper Liquid.
Pros and cons of this method:
PROS: Skips the low wines process and the associated time delay.
CONS: Dilutes the alcohol content of the collected spirit. Doesn’t extract as much flavor.
Experiment, and Have Fun!
Thumper kegs add a certain amount of pizazz to a pot head distilling system. Not only do they look cool, the “thump… thump… thump…” sound they make while operating adds an auditory signal that all is going well in the distilling process.
Being able to easily extract flavors from fruit, botanicals, oak, or anything else you dream up adds a whole new dimension to flavor design.
If you don’t have time for multiple distilling runs… If you like the idea of flavor design… If you like a higher proof at collection while getting a refined spirit… then consider adding a thumper keg – or even a series of thumper kegs – to your distilling system.
Questions? Click HERE to “Ask Jaybird” – NorCal Brewing Solutions in-house distilling expert!