Another old hillbilly type of distilling method that has started to make a comeback in recent years is the use of a thumper with your moonshine still. Also known as a “thump keg,” the anatomy of a Thumper Still is similar to that of an Alembic distiller with an extra piece of hardware called a thumper that goes between the boiler kettle and the condenser. The purpose of the Thumper Still is to provide you with a finished product that is very similar to what you would achieve if you were to re-distill a distillate that was first run through a pot distillation. Another nickname for the thumper is “doubler,” but don’t let that fool you: Using a Thumper Still doesn’t DOUBLE the purity of your distillate, although it does increase it. The term “doubler” is in reference to the fact that using a Thumper Still is similar to double distilling.
A Thumper Still works like this: You boil your wash in your kettle and the vapors pass through the tubing and into the thumper, which is already filled about halfway with a liquid of your choice (e.g., water, fermented mash). The hot vapor from the kettle enters the thumper through a tube and exits that tube towards the bottom of the liquid inside of the thumper. The hot vapor heats that liquid, which at the same time cools the vapor in a heat exchange. Initially, no vapor comes out because the temperature has been reduced, but the temperature of the liquid in the thumper rises as the distillation process continues. Then lower-boiling-point compounds will vaporize and rise, exiting the thumper through the condenser and dripping into your collection container.
So now you can see how the thumper part of the Thumper Still works as kind of a second distillation, because when you use one, you are basically double distilling, or doing two runs in one. The lower temperature that occurs in the thumper during this second distillation allows many of the by-products and water to stay in the thumper since the temperature remains below their boiling points. Therefore, distillate that leaves the thumper is actually at a higher percentage of alcohol than the vapor that leaves the kettle.
Something important to keep in mind is the size of your thumper. If a thumper is too small or if you didn’t put enough liquid in it, then that liquid will heat up too quickly from the incoming vapor. Then that vapor will just bubble up right through the liquid without being cooled and condensed first, exiting straight through the condenser. In that case, you don’t achieve the second distillation and don’t see the increased purity or proof from it. On the other hand, if your thumper is too big or if you have too much liquid in it, the incoming vapor won’t be able to heat the liquid up properly. Then all the vapor is condensed and actually becomes diluted by the liquid in the thumper, which is the exact opposite of what you want. Overall, Thumper Stills are great for when you want to achieve a higher proof and purity in less time for less money, but you will want to do your research before buying or building one to ensure that you get the right size that will meet your needs.