How does a Thumper keg work?

[Dolmetscher]

So, I understand how a pot still works.

And a reflux still is just a pot still with a long column, with "something:" rocks, perforated discs, copper webbing, etc. in the column so that the water "sticks" to the material and drips back into the still, and a more pure ethyl alcohol makes it through the material and into the worm to condense back into the liquid.

Now, I've seen all this stuff about "thumpers" or "thump kegs." I've never seen one in real life, so... if you will indulge me... I'd like to tell you guys what I think they are, and you tell me if I've got it.
A thumper is a vessel, partially filled with some inert liquid (water, extra mash etc.). The still's head has a pipe that comes out of the pot, and goes into this thump keg, and the tip of the column is submerged in the liquid. So, the alcohol vapors travel through the column and into the water inside the thump keg, where they emerge as bubbles of hot alcohol steam. The bubbles rise through the water and pop, releasing the alcohol into the keg, which then travels through a "release pipe," that goes into a worm/condensor... and comes out as a high proof alcohol. The theory being that the water, being cooler than the steam, condenses what little water is in steam, allowing for a more pure alcohol. It most likely also somehow "scrubs" the steam of some impurities, and heavier molecules... kinda like a water-bong in college.

Is this true? If not... please set me straight.

[Richard7]

Dolmetscher, from what I understand that is about half of it. The thumper is also heated by the steam and becomes a "second boiler" kind of like two distillations for one. Your description of the flow sounds spot on.

[Usge]

Not exactly...but close. A thumper is a parasitic secondary boiler. For it to work like it traditionally should work...you need to start with some alc in the thumper (ie., wash or low-wines, feints, etc). You only start with enough to cover the input tube at the bottom. The alc vapor coming over into the thumper condenses as it bubbles into the liqiuid which fills the thumper, increases the abv of what's in the thumper and heats the solution at the same time. Remembering your theory...the higher abv solution in the thumper will now have a "lower" boiling point than the pot that is driving/feeding it. This is what you want. Once the solution in the thumper heats to it's somewhat lower boiling point..it will pass off higher proof alc vapor through the output tube where it goes to condensor. The pot continues to heat and feed and drive the thumper. It is in this way that it's a secondary/parasitic boiler.

Think of it as one giant bubble cap plate. What you are looking for using a thumper is not double proof. It should start at slightly higher proof, but sustain it longer through the middle of the run (instead of it dropping linearly as it normally does on a potstill run). It's about equivalent of 1.5x distilling. It also depends a lot on how much volume you have in your pot (how much alc) as well as the proof, and what you start with in your thumper. Starting with water in your thumper means...it has to fill, raise the abv, and heat up to a higher boiling point before it will start working and kick in. It takes longer to start, and it uses more alc from your pot to get it primed and online. You can also use "Flavorings" in this way. In my experience with them...they work better when running off a pot full of low-wines than it does when trying to single run wash through it and starting with some alc to prefill the thumper (ie., wash and/or lowwines). YMMV.

[OBX Phantom]

+1 Usge

I use a thumper, and Usge is absolutely correct, a thumper really doesn't raise your ABV more than 1 or 2%, but it does however work as more like a filter to get more of the impurities out. And it also keeps your ABV more consistant through the run then drops off more abruptly towards the end. He is also right about it doing better with higher ABV. runs. so you still need to do stripping runs, and save up your low wines and feints for a spirit run through the thumper.
If you do a search you will find a thread called "adding a thumper" that I put up on here about a month ago. In it you will find no.s from my spirit run, and also more explanation.

[Bama1981]

running a SS stove top pot still without a thumper my heads came off at about 105 proof, with a thumper the heads came off at 160 proof. The middles held at between 140 1nd 150 for a long ass time. MHO, if you are running a pot still without a thumper you are wasting your time. The magic of the Thump Keg is in how you charge it. I charge mine with the tails of the previous run. If you have no tails you can use some of the wash, but I would suggest a trip to the likker store and buying a cheap ass bottle of white store bought shine (Midnight Moon or Georgia Moon). It's too nasty to drink, but it's 80-90 proof. After the initial run you will have tails or backings to charge with. Also, Be sure to place a pad or type of heat barrier between the thumper and what ever surface is under it(if you care about the surface).

[Dolmetscher]

Thanks Bama1981...

Quick Question... When you read on bottles of Vodka, it sometimes says "Distilled 6 times" etc. And I've heard that Bourbon in KY is often distilled 3 times. I know that this is done to get rid of impurities. And that each time you run it through the still, more and more impurities are removed and the ABV of the end product goes up. What I do not know, however, is... do people really take highly flammable distillate coming straight from a still, then dump out the leftover crap, wash out the still, and then pour the distillate right back in at like what, 80-90 proof (?), and then set it over a flame to heat up in a metal container, without thinning it out with like distilled water or something to reduce the ABV so that you aren't just creating a alco-bomb?

[Danespirit]

No,no,no....You have to dillute it to below 40%..!!
NEVER fill your boiler with undilluted product and attempt a distillation, it's simply too dangerous..!!
That will also support the "cleanup" of your product.
Please take a look at the link in my signature...it will answer a lot of your questions.
+1 USGE...a perfect explanaition of how a thumper acts in the chain of distillation.

[rad14701]

There are methods of diluting your low wines so they that the %ABV of the final spirits are very close to your desired final proof... Do some research around here in the forums as well as on the parent site and I'm sure you'll be enlightened... There should be calculators that can be used as well... Start with x% ABV wash, distill to y% ABV low wines, and then distill again for z% ABV final spirits... Toss in an initial hard and fast stripping run on the front end and you'll have XXX (triple run) distilled spirits...

Having purchased and consumed several of the legal white dog brands currently on the market it tastes like they have ended up with final spirits at too high of a proof and have subsequently tempered down to target proof with excessive amounts of tails instead of water... Try to avoid this because without ample aging time it will be hard to mask the tails taste and smell...

[aircarbonarc]

I'm actually curious about stuffig my 3" potstill column with copper wool and then running a thump keg if that would make 2 distillations in one. Usually I run my rum and whiskey twice. With a 87-80% prime hearts run and then a quick cut for tails. I'm sure I could do this with a thump keg and if I used some low wines with some wash as thumper juice. What I'm concerned about is flavor, that's something I don't want to compromise on.

[S-Cackalacky]

Stuffing a pot still head with copper mesh won't accomplish much. If you want to retain as much flavor as possible, charge the thumper with wash. I run apple brandy with a single run with the thumper attached with both the boiler and thumper charged with the same wash - gives lots of flavor.

The thumper will cause some smearing of cuts. Best to run real slow drips through the fores and into heads and then speed up to a pencil lead sized stream for the hearts and tails. This will help to keep some of the heads out of the hearts.

[kimbodious]

Is it suitable to put backset in the thumper keg say if it is still around 4% ABV?

[goose eye]

Yup but what is you lookin for.

So I'm tole

Ps. What is the 4 percent from? All juice all grain
So on an so forth.
You can stay up the better part of the night reckonin . Just do it an find out.

[kimbodious]

I was looking for adding more flavour goose-eye, probably not by that way aye.