Reflux theories, opinion and experiments

[mash rookie]

Passive reflux. Almost any still head without packing has some passive reflux as liquid cools on the sides and returns to be re distilled. By adding packing this passive reflux is increased dramatically. Height of column and packing can create significant HETP’s Height equivalent to theoretical plates.

Imposed reflux. This describes the affect of having an interior cooler to create additional reflux above packing to a certain level of HETP’s Cooling management and Vapor management columns use interior coolers to condense vapor so it will be re distilled within the packing.

Recycle Reflux. This is how a plated still works. Plates are intentionally flooded to a determined level before liquid is returned to the plate below. By keeping plates flooded, upward rising vapor must pass through the liquid taking the higher volatiles with it.
The result is a very high ABV is created with Recycle reflux.

I want to explore what I refer to as the temperature gradient and reflux gradient of a passive reflux column (packed) and imposed as compared to a recycle reflux column.

Some things have become more clear to me as I understand the function of my flute and the comparison to commercial plated units and packed columns.

First was to comprehend how a four plate flute will produce a constant 90-94% ABV but not make a neutral. Recycle refluxing explains to me how high ABV can be reached with few plates. My flute makes a heavy spirit (I believe) because of the higher temperature necessary to drive vapors up to the interior cooler. Thereby taking the higher boiling temp congeners with the hearts into the system. Tails. Hence the heavy flavor and inability to make neutral even at 90%+

I believe it is an incorrect statement that tails are compressed. The reason tails do not appear at the end of a batch run is because they have already been distilled with the hearts. There are little or none left to collect.

Obviously there is a reason commercial units have taller columns with more plates. Without understanding taller columns, I assume that the upper plates are necessary to separate fractions. To quote Rad “ Height equals quality, Diameter equals volume” I am not sure if this theory can be refuted. It may be a statement of physical law.

On a packed column of equal HETP’s I believe there is a reflux gradient relative to temperature inside the column. Although there is constant refluxing action taking place, the congeners never make it past a certain point. This passive refluxing allows for better separation of fractions. Imposed reflux improves this action rather than change it.

My first experiment will be to replace my flute tree with packing and one top plate with a short centering down tube. This should allow the Dephlag to operate in similar fashion creating reflux now as Imposed rflux. The difference being that condensed liquid is not returned completely to lower plates leaving the gradient refluxing intact.

Will I achieve similar ABV? Will I produce a cleaner neutral? Will I run at similar temp?

I strive to understand is vapor speed in relation to packing and refluxing action. A different design will require this knowledge. Another post. Another time.

I had forgotten how much valuable info is on the parent site. The more I understand the more questions I have.
MR

[Odin]

Mash, my friend, I love your post and your explorative mind. Looking forward to hearing more about the results of your trials with packing instead of plates. A few questions and a remark or two, though.

Q1: why don't you take out the top plate as well and let the dephlag on your flute do all the condensing and your newly inserted packing all the refluxing action?

R1: I have an old style CM rig that is not a plate/cap style rig with recycle reflux, but the type with imposed reflux. Reaches 96.5% everytime (well, as long as I don't flood the column completely). Not only does it yield azeotropic results, also (being a CM) it holds back tails really well. Compressed tail? Very much!

Q2: Or should I say, after reading your post, "the reason tails do not appear at the end of a batch run is because they have already been distilled with the hearts. There are little or none left to collect."

Q3: Now, if my rig als "compresses tails", using CM and an "imposed reflux", doesn't it do the same as a flute? Getting over all the congeners from tails?

Q4: To make your research complete, and make sure it is not just the CM style reflux management in stead of the difference between flutes and recycled reflux on the one hand and non-flutes and imposed reflux on the other hand, would you mind if I take on the other part of the test?

Q5: ... and put - say - beer stripped UJSSM at around 32% and put that through my CM imposed reflux rig? "Compressing" tails as much as possible?

R2: The result will be 1 or 2:

1: If I get a neutral out of it, your theory is credited and flutes do something different as compared to stills working with imposed rather than in recycled reflux.

2: If I do get over a lot of flavour (and allmost no tails in the vessel - I will measure the ABV there as well), it is likely the CM style cooling does something like compressing tails, while getting over the tails congeners, wheter it is through a flute and recycled reflux or a rig working with imposed reflux.

I hope for number one! Let's hope the magic flute produces magic! On the other hand ... if I can make a 96.5% pure UJSSM that actually tastes like UJSSM instead of like a neutral ... than I would not have to build a flute!

Mixed feelings on this. But very positive on the explorations, investigations. Pushing the boundaries of distilling science some more, MR!

Odin.

[mash rookie]

Mash, my friend, I love your post and your explorative mind. Looking forward to hearing more about the results of your trials with packing instead of plates. A few questions and a remark or two, though.

Q1: why don't you take out the top plate as well and let the dephlag on your flute do all the condensing and your newly inserted packing all the refluxing action? The top plate will be for raising the final ABV on distillate that has not been recycle refluxed.
R1: I have an old style CM rig that is not a plate/cap style rig with recycle reflux, but the type with imposed reflux. Reaches 96.5% everytime (well, as long as I don't flood the column completely). Not only does it yield azeotropic results, also (being a CM) it holds back tails really well. Compressed tail? Very much! If it holds back tails you will have a clear line from hearts to tails and vry strong tails.
Q2: Or should I say, after reading your post, "the reason tails do not appear at the end of a batch run is because they have already been distilled with the hearts. There are little or none left to collect."

Q3: Now, if my rig als "compresses tails", using CM and an "imposed reflux", doesn't it do the same as a flute? Getting over all the congeners from tails? No. Tails can only be avoided or not. Not only does the flute take more heat to function, Recycle refluxing relies on plumbing to move the liquid to lower plates where it is exposed to tail vapor and congeners. A constant mixing that your rig will not do.
Q4: To make your research complete, and make sure it is not just the CM style reflux management in stead of the difference between flutes and recycled reflux on the one hand and non-flutes and imposed reflux on the other hand, would you mind if I take on the other part of the test? You are of course welcome to particapate. That is how it is done here.
Q5: ... and put - say - beer stripped UJSSM at around 32% and put that through my CM imposed reflux rig? "Compressing" tails as much as possible? (Avoided as much as possible)
R2: The result will be 1 or 2:

1: If I get a neutral out of it, your theory is credited and flutes do something different as compared to stills working with imposed rather than in recycled reflux. You will get little flavor at that ABV with your design unless you can run it hotter.
2: If I do get over a lot of flavour (and allmost no tails in the vessel - I will measure the ABV there as well), it is likely the CM style cooling does something like compressing tails, while getting over the tails congeners, wheter it is through a flute and recycled reflux or a rig working with imposed reflux.

I hope for number one! Let's hope the magic flute produces magic! On the other hand ... if I can make a 96.5% pure UJSSM that actually tastes like UJSSM instead of like a neutral ... than I would not have to build a flute!

Mixed feelings on this. But very positive on the explorations, investigations. Pushing the boundaries of distilling science some more, MR!

Odin.

Thanks Odin. I will post again to try to explain my theories better.

[Odin]

Loved your theories & explains, MR! Just thought I would jump in from the perspective of "what does a cm still with imposed reflux do? Not because I think your theory is flawed, but because the only way to make sure, is to rule out other explanations.

I guess I will do my test on the upcoming weekend. Wil let you know my results asap! Think it will be a neutral as well, because my Ian Smiley approach to making whiskey (he uses a LM rig at 95% - 92%, I tried my CM rig at 96.5%) with feints did not give me what I expected. An "Eau de Vie de Whiskey" at most. Interesting, but nothing like "a real heavy whiskey" comming over.

Anyhow, results will follow!

MR, PM-ed you to compare some JD chips results on UJSSM. If you find time to reply ... much obliged!!! Odin.

[mash rookie]

"what does a cm still with imposed reflux do?

After gradient reflux in the column the cooler forces additional refluxing at the top of the column raising the ABV off what is already pretty clean spirits. The same action as I expect from placing one flute plate above my packing.

I ran a still like yours. The same design except that I had no cooling lines in the vapor path. Passive reflux only. Only input temp changed results. This previous experience has helped me understand what is happening on my flute. When run very slow, I could achieve a clean neutral at 85% When run hotter on UJSSM it would pull more flavors through at 75-80% It made some darn good stuff.

That is why I had suggested to you before to run your UJSSM faster through your rig. You replied that it would flood. The idea is to pull more tails and flavor for UJSSM.

If you want to make flavored spirits like UJSSM or all grain with it you could to modify the reflux cooling. Using only passive reflux at a higher speed would allow a one run and done scenario for quality whiskey. The results would be similar to a double pot still action. Another option is to add more tails in to your final blend.
Your model of still could benefit from having a diverter valve to regulate how much coolant flows through to top of the column. It would give you control for running different washes.

This a completely different action than what we experience with a flute and why flavors are different.

MR

[Odin]

MR,

I am going to build a still with column and some dense packing, but no cooling, other than productcooler. The packing and height should up the reflux to effectively 70% to 75% in one run, I guess. Want to use that to do my UJSSM's in one run. I already have a 2 inch wide, 30 inch tall copper column ...

Also in the process of buying a 50 liters olive can (?), that will serve as my kettle!

Odin.

[Usge]

On my 2" bubble plate, it will pull 90% (with flavor) as well. The difference is...it does it at drip speed and it's hard to stabilize. This is more a function of the column diameter than the plates I think. I built mine to see if it would function the same as the 4 inchers (ie., 90% at potstill speeds). It doesn't.

I've had some similar thoughts along some of those lines MR...particularly about "compression" of heads or tails. Still experimenting myself But, I can tell you right off the bat...packing mesh, will give more plates than "4". Part of the reason for the less than pure separation is that you are only running 4 plates. A comparably sized/length tube full of inert packing material...(ie., mesh, etc), would deliver far more separation mostly because it has more HETPs. The dephleg (CM) is what is also part of the reflux equation. Basically, you can take a tube, put your dephleg at the top of it, and even with minimal packing you could pull 90%. (I did it on a 36" tube with 12" of copper mesh). This appears to me to be more a function of the CM of the dephlegmator. I think the last bit is also true that because of the way the plates function, bubbling through liquid, somewhat like thumpers, only adds to the flavor....as you have noted. As far as the smearing of tails flavor..etc., this is also a common issue with thumpers in my experience. There are ways to minimize it, but in general, if you were to run a thumper the way you run those bubble caps...you'd get the same kind of smearing...and it works exactly the same in regards to tails...falls completely off when it's done..cause the tails are already expended in the liquid. That's just been my observation.

Look at how LW built his latest thumper. It's inline..with the thumper over the pot, drain back down, and a dephlegmator over the top. If you think about it, it's one giant-ass bubble cap. He also can get high proof very flavorful distillate from his still...and would be hard pressed to make "vodka" with it I"m sure. I feel certain that he could add to this discussion and some of your questions...in how he deals with some of those issues (smearing, etc) as well.

Lastly, I went back and read some old reference material. It's always a joy to go back through the main site and read things...and remember passing through them at some point but never really understanding them. I also went back through Mike Nixons Complete Distiller. It also discusses these stills in terms of the type of reflux and how it works. I think he calls your "imposed" reflux, "compound" reflux (passive, plus induced/forced). But, I think the one thing that stuck out to me in my research on "smearing" issues....and take off speeds, etc., was that there is a pocket right near the take off that needs to be stable. The vapor speed going up, and the amount taken off, vs what is returned...forms a stable area/pocket for drawing off. If you draw off too fast...you "pull" the lower volatiles up quicky...squash this sweet spot..and smear the vapor. You are then just pulling what comes off the pot up the tube. If you balance everything right...the idea is that what is coming off, is replaced in such a way by lighter portions coming up through the column to maintain this pocket in a stable way..ie stabilizing the column. When this gets out of balance, the vapor temp will rise. The gist of it is..a taller column has a longer gradient in the tube...and it is thus easier to maintain this. This is a quote from the book;

Over time, the most volatile component will find its way to the top of the column, and the less volatilecomponents will work their way downward, establishing a state of equilibrium. The top zone of thecolumn will have a constant temperature, equal to the boiling point of the most volatile componentconcentrated there, and it becomes a constant composition "reservoir zone". Below this zone,temperature increases as you move toward the boiler as the normal interchange between vapor andreflux condensing in the packing re-asserts itself. The net effect is to shorten the fractionating columnas space is needed at the top for this "reservoir".

When you begin to remove some of the top condensate, rather than return it to the column, theequilibrium is disturbed. If you draw it off very slowly, the column can adjust and form a newequilibrium as the fractions lower down slowly move up the column. If you take it too quickly,equilibrium is lost and the whole device reverts to behaving like a simple fractionating still.

A simple fractioning still (packed column with no reflux condenser) depends heavily on heat input (steady slow vapor flow) in order to fraction properly.

I think it would be a very interesting experiment to combine plates and mesh to see if it might be possible to fine tune your column's reflux for the flavor profile you want. Interesting discussion MR!

[The Baker]

I am not very expert on all this, (especially because I use a pot still, not reflux) but, suppose...

that you had an additional take-off set-up at the BOTTOM of the column.

One good way to do this would be to feed the hot vapour in, say, at the SIDE of the column
a bit above the bottom, and fit the additional draw-off tap in the base.
But it would be simple to do it differently if your column is mounted in the lid of the boiler.

(I just have not figured out the detail but trust me it would be simple.)

The advantage of having this second drawoff point below the entry point
from the boiler is that you would not be taking any of the partly-new material away, just what has already been 'fully' refluxed.

Anyway you have a little tap, same as you have at the regular draw-off point, to regulate the amount of more- or- less spent wash drawn off.

Then when the still comes to equilibrium, set it so that as well as the small amount of good spirit coming off at the top, a (similar? bigger?)
amount of (low alcohol/ almost no alcohol?) 'product' is drawn off at the bottom; not too much, so as to maintain the equilibrium of the still.

Okay, this is not earthshaking stuff, not really a new idea.
But we don't DO it, do we?
Everyone knows that the vapour at the bottom of the still is lowest in the good stuff, because the good stuff is at the top.
But we continue to run the low- to- very low alcohol material back into the boiler where it has to be re-heated;
drawing off a little of it should make the still quite a bit more efficient in terms of energy use and could well improve the product
(which is a question beyond my expertise but I think the product would probably be better and is most unlikely to be worse).
Probably the liquid thus drawn off would be of little or no use (almost no alcohol or flavour) but if that were not the case you
could put it into your next fermentation; no loss.
And if you did, the small amount of alcohol in it would not affect the fermentation of your new wash,
especially if you added this drawn-off material late in the fermentation.

And to add the second draw-off tap costs practically nothing to do, especially if you are making a new still.

Afterthought; probably you would get sufficient condensation at the base of the column (if the side entry point from the boiler is a bit above it)
to draw off these quite small amounts as LIQUID, but it should not matter if it were vapour, a few coils of tube should act as an air-condenser?
Certainly there would be a simple work-around of this if needed.
What do you think?

[mash rookie]

Usge,I had a long conversation with Larry yesterday. He has some interesting thoughts about reflux theory. I think I understand his rig but have not seen pictures or a drawing so I am a little vague. His thumper design seems to do exactly what he wants. Make great rum. I would like to know more about it.

Yes, the parent site really is incredible with the quality of information. I had not only forgotten how much I learned before coming here but I now understand so much more after being here and learning from you guys. It takes awhile to absorb all the information.

When discussing reflux gradient it is important to include time as well as temperature. I agree that the stable pocket/ maintaining equilibrium is an interesting consideration. That brings me back to wanting to understand vapor speed theories.

My opinion about dephlag or cold finger type coolers is that they simply force additional reflux. The results depend on what is happening below them. If used above a recycle plate system or packing will change results.

One of the interesting phenomenon’s is the temperature change in a simple column as hearts change to tails without changing boiler settings. We all accept this as what happens but why? Do the heart actually hold back the tails? With volumes changing very little, Why does temperature change with alcohol %. Shouldn’t it be a direct reflection of BTU’s applied?

Baker thanks for chiming in. Great post. I was going to go there some time in this post after soliciting theory opinions but here goes.

Recently I toured a small micro distillery and had a chance to look at their still. It’s configuration may be an answer to what I see as the problem with my flute of excess mixing of congeners (tails) with my hearts.

There still was about 50 gallons (guess) with a 10-12 inch diameter five plate bubble cap design column. I am not sure of the manufacturer but I have seen pictures of them before. A beautiful all copper design.

The Boiler is configured with an expansion chamber above. Vapor taken off there is introduced to column below the second plate. The lower first plate had a pipe returning to a lower point in the boiler. The gentleman explained that what made it down to the first plate was returned to the boiler. This may be a reasonable way to separate tails before they enter the recycle reflux system.

There was a bubble cap on the first plate so it was not just a drain. The pipe appeared to return above what liquid level would be. That would indicate that there would be vapor rising as liquid was falling. Secondary distillation of tails?
Ther still had a net four plates like mine. More food for thought.
MR

[LWTCS]

MR
BTUs applied might be confusing you........remember water boils at 212. Not 250,,or what ever....that's why no matter how much heat we throwat the boiler the tempwill never exceed 212......long as the boiler has liquid that is.

[mash rookie]

MR
BTUs applied might be confusing you........remember water boils at 212. Not 250,,or what ever....that's why no matter how much heat we throwat the boiler the tempwill never exceed 212......long as the boiler has liquid that is.

Hi Larry. I am confused daily.
Is that to say that we can not boil alcohol at 212 degrees? Wouldn’t it just be mixed with water? On a very hot surface water will boil off faster than a cooler surface that still boils. I would argue that with enough heat you could boil water at higher temperatures. It would just boil off faster.
That being said, liquid does seem to have a temperature limiting ability. I monitor my boiler temperature. And yes every wash boils at a different temp depending on the ABV.
It is interesting that if I crank the heat up when distilling (within reason) the temp will rise by one degree or less but vapor and vapor speed will increase dramatically. Even agreeing with you I find temp changes with the same BTU's interesting.

If I am to take your statement as absolute then my earlier thought that tails are pulled through in part because of higher temperatures required for my flute is incorrect. That would mean that it is only a result of the recycle reflux action.
Thanks,
MR

[LWTCS]

The amount of abv within your boiler charge will determine your boiler temps. And as the alcohol is liberated from the bulk amount of water,the temps will rise. But not exceed 212.
So the trick is to apply the optimal BTUs for your desired outcome.

[mash rookie]

The amount of abv within your boiler charge will determine your boiler temps. And as the alcohol is liberated from the bulk amount of water,the temps will rise. But not exceed 212.
So the trick is to apply the optimal BTUs for your desired outcome.

I get how it works in practical application, I just don’t completely understand the technical physics behind it. I do find it interesting.

No matter. My main investigation here is the refluxing patterns and how to manipulate them for my desired outcome. I am going to run some rum and all bran through my flute before doing any modifications. Maybe by then I will have the new rig ready to test. It will have a little different reflux theory and mechanical design.

[Usge]

One of the interesting phenomenon’s is the temperature change in a simple column as hearts change to tails without changing boiler settings. We all accept this as what happens but why? Do the heart actually hold back the tails? With volumes changing very little, Why does temperature change with alcohol %. Shouldn’t it be a direct reflection of BTU’s applied?

I'm no expert on anything MR, particularly bubble plates, but the answer to that question on first glance would appear to be a very simple one based on the boiling points of a water/alc solution as the alc is depleted (ie., the boiling point rises). This happens naturally as part of the goings on "inside" the column. You have to remember that there's heating/cooling going on inside the column separately from what's going on in your boiler. The reason your column can maintain a given vapor temp or equillibrium is because there is cooler, lower boiling point compounds at the top that are being replaced as they are taken off. As the alc is depleted towards the end of the run, the temp gradient is going to rise and it eventually will destabilize and "squash" that "reservoir" zone near the take off and the compound with a lower boiling point that was once there, and maintained, will be replace with one that has a higher boiling point. On straight up fractioning tube (with no reflux condenser), the only way to control this is by "heat"/vapor speed vs take off rate. In other words...you have to run it SLOW. Perhaps stripped of all the other complexity, these factors can offer some insight.

The function of your boiler heat is more related to vapor "speed" going up the column. That has to be balanced with everything else within a certain range to maximize separation. Beyond that, it just forces vapor straight through. If you want to check that, according to advice/reading, a good average for min/max vapor speed range would be above 12" per sec, but below 20". The math (which was kindly shared with me) would be Watts = VaporSpeed x Diameter squared)/58.3 with results given in "kilowatts". We'll figure yours for using a 4" column:

Watts = (12 x 16)/58.3 kw = 3.3 (3,300 w) minimum vapor speed
Watts= (20 x 16)/58.3 kw = 5.5 (5,500 w) max vapor speed

Just for comparison, here's the numbers for a 2" column:
Watts = (12 x 4)/58.3 kw = .8 (800 w for min vapor speed)
Watts = (20 x 4)/58.3 kw = 1.37 (1,370 w for max vapor speed)

Just from looking at that, I think it's quite clear why a 4" column outputs far more volume of compared to a 2" column of the same design! Its also another way to look at/confirm the saying...height is for purity, width is for volume/speed. A good middle ground for your 4 incher might be 16" per sec and you'd want to run your boiler at 4.4 kw (4,400 watts) for that. Note that "height" has nothing to do with this formula.

As you know...I'm chasing down a lot of demons too and trying to gain a deeper understanding of things. Ultimately, I think that what I'm looking for is more "control" over things, which I find very elusive at times. I get reminded of it almost daily . I recently went back and re-read The Complete Distiller. I had read it a few years back..but I think I just wasn't at the level to really get deeper into it. So, I'm enjoying it now and feel like i'm getting more stuff from it. But, everytime I feel like I start to understand a bit....something happens just to remind me...that there's "variables" all the time. It sometimes feels like chasing your tail. (no pun intended).

Edited: to correct "kw" to "w" (kilowatts to watts). Results for formula are given in "kw", then converted to watts. Also, to add that some sources clarify the above math to suggest it is for "mesh" packed column. Some sources suggest middle figure between 12 and 20" per sec as optimal, while other sources suggest the top as "max", 12" per sec as optimal, and that there is no "minimum" speed for vapor that would destabilize a column.....only a maximum.

[LWTCS]

My main investigation here is the refluxing patterns and how to manipulate them for my desired outcome.

Not trying to drift but consider this:

We have seen rad offer advice all the time to the new Bok operators. They get their stills christened and then a run or two more and are still only able to pull 92-93. So rad tells em to push a bit more heat rather than slowing down. Seems counter intuitive,,,, but what he is actually recommending is to produce more reflux. More reflux will more throughly wet the packing and and make for more phase change. Or more distillations occurring within the column.

In your case you need to push enough heat/pressure to produce enough vapor/reflux to stack your plates and hold the liquid on the plate. The heat you are using to do this is likely the reason you find,,,,,,,the strong flavor through out your run.....

[mash rookie]

Not sure yet LW, it might be a combination of both. Temp/ vapor speed or recycle mechanics. It will be interesting to see what happens when I do the modifications.

usge, I am still trying to digest the vapor speed info. The first thing that occurred to me is how would I measure it? If it is theoretical numbers how do I apply them? I have to assume that guys with larger stills have to use more heat to create enough vapor speed thereby throwing congeners into the column. What is different?

I am going to go back and re read the parent site some more.

I am a little surprised that we have not had some of our other big brain guys chiming in?

I will try to post some better questions next week.

[Bagasso]

MR, first thing we have to remember is that heads, hearts and tails are just general terms to describe a mixture of a lot of chemicals. Also, that even these are often divided into early, middle and late. So, as far as tails and flutes go I think you may be right but it may just be the more flavorful chemicals in tails being pushed through the hearts and the more bitter nasty chemicals in tails may be held back (instead of compressed).

Now I think flutes act more like a series of thumpers and not really like a column. That is the reason that it can push distillate in the 90's and still have full flavor.

I've read flute runners say that the plates empty as the run winds down. I think this is what would happen if you had thumpers placed in stepped fashión (like on a flight of stairs) each with a small diameter drain at the bottom to the previous thumper. Once the vapor in the previous thumper became too little keep the pressure in the line the upper thumper would drain to the previous one until, eventually, they would all be empty.

This makes them act differently than a gradiant in a column.

[Odin]

Hi all,

I did a post on another topic MR posted. It is about how to operate an Holstein. I think it is important to know how & why that is done the way it is, because there are similarities with the Magic Flute design. If I remember well, OD started building his Magic Flute to get close to something A. Holstein makes professionally.

Here is the thread:

http://homedistiller.org/forum/viewtopi ... 3#p6926853

What I learn from the German University at Heidelberg on distilling & from how to operate a Holstein rig, is that vapour speeds and power management and cooling management are critical to getting to what you want. Just like posted before on this thread.

Odin.

[Odin]

Q3: Now, if my rig als "compresses tails", using CM and an "imposed reflux", doesn't it do the same as a flute? Getting over all the congeners from tails?

Q4: To make your research complete, and make sure it is not just the CM style reflux management in stead of the difference between flutes and recycled reflux on the one hand and non-flutes and imposed reflux on the other hand, would you mind if I take on the other part of the test?

Q5: ... and put - say - beer stripped UJSSM at around 32% and put that through my CM imposed reflux rig? "Compressing" tails as much as possible?

R2: The result will be 1 or 2:

1: If I get a neutral out of it, your theory is credited and flutes do something different as compared to stills working with imposed rather than in recycled reflux.

2: If I do get over a lot of flavour (and allmost no tails in the vessel - I will measure the ABV there as well), it is likely the CM style cooling does something like compressing tails, while getting over the tails congeners, wheter it is through a flute and recycled reflux or a rig working with imposed reflux.

Mash,

This weekend I did my test. Instead of running UJSSM at 31% through my CM fractionating still, it was Gerber. More neutral, less taste than UJSSM, so even better suited for the test I proposed to help us all at delving deeper into distilling theory.

I got a perfect 96.5% ABV. And heavy taste notes came over from tails. Tails as in "left in the boiler" were very compressed.

Because of this result and because of what I read about what Holstein does in order to get taste over from heads to hearts, I think that the taste getting over can be provoked by the CM style both mine & the Magic Flute have.

Odin.

[mash rookie]

Not quite understanding what you did Odin. Did you pot still Gerber then run through your CM? Did you make cuts on the first run? Can you explain the cuts on your second run? Are you saying that you pulled tails through flavoring your hearts and had little left to collect?
Isnt Greber a neutral product? What kind of flavors were you looking for?

[Odin]

MR,

I took an interest in your thread. Maybe the flute design does something different and that might explain taste/tails. To make sure that it is not "just" the CM cooling in the top, I proposed (and executed) an experiment that might help us further in thinking about how distilling works. So I did something I usually do not do: put a low in taste (relative) Gerber wash through my CM fractionating still. Could it get over taste congeners from tails, without actually bringing over the tail alcohols?

A Gerber wash is pretty neutral, but not 100%. It is made (mine) from mostly weat. Taste is there, but compared to UJSSM or All Bran it is not much. Compared to a turbo sugar wash, there is much more taste in a Gerber, though. Just for giving it a position relative to other recipes.

First a did a stripping run and I collected pretty much any alcohol present. Then I put these low wines in my fractionating still. Fired her up and started collecting at 96.5%. I noticed that heads were less in quantity and less smelly, compared to a turbo wash. Pretty soon I could start to collect hearts. Almost no smell or taste. Maybe a hint of sweet, just like other pure & neutral drinks I make. Still collecting at 96.5% here. Now, in general on a sugar based wash I cannot collect any tails. Temp stays rock steady at 77.5 degrees and than drop, signalling the run is done and giving me just enough time to switch containers before an extra gulp of mainly water comes over, really telling me it's over. Now this time, I did not go that far even. Still, towards the end of the run (I made a calculation of the amount of ABV I could get over from my low wines, collecting the spirit run at 96.5%), I could taste a difference in taste. Strong flavours, wheaty/whiskey like, came over. And I mean strong. Not bad. Contrary, pleasent (though too much in intensity & strength), but not what you expect trying to make a neutral. At this phase I was still collecting at 77,5 degrees on my temp measuring rod and at 96.5%).

The drink I finally got, when watered down to 45% ABV, had a distinct grainy character. No vodka. Not by far. Not a whiskey either. Something in between?

Almost no ABV left in the boiler less than 2% is what I measured in the remainings when cooled down. Isn't this what is happening to flutes as well? Containing, compressing tails, but getting over taste? Now my taste must have been less than it's full Gerber taste potential when potstilling, but that is to be expected at 96.5%. There is just almost no "place" left for taste to get over. But "getting over" it does, at the end,in abundancy. Since I do this with a CM still that is not a flute, can these findings signal that - since both my rig and flutes work CM style - it is the CM style cooling that creates these interesting "compressions" of tails yet hauling over taste?

Odin.

[LWTCS]

Odin.
Kiwistiller and a few others (as I recall) have commented that their CM's make a very good white rum.

[Odin]

... which is interesting, because in general it is thought that when distilling at/near azeotropic conditions, you turn pretty much everything into a neutral, no? That's pretty much how I understand others who run LM or VM's ... MR, LWTC, are we on to something, here?

Odin.

[rad14701]

My personal opinion is that CM's don't produce spirits in the same manner as LM's or VM's... With an LM I get the same compression of heads and tails, and rarely collect this small quantity of tails... But my hearts stay cleaner than I have heard about CM's producing... With my LM I get virtually flavorless neutral hearts unless I intentionally run fast which increases vapor temperature and lowers %ABV of the spirits collected... At some point I'd like to add a VM branch option onto my LM column to see the difference but experimenting with a true CM would be a ways down the road if at all...

[mash rookie]

Odin.
Kiwistiller and a few others (as I recall) have commented that their CM's make a very good white rum.

Larry, I used to run a CM like Odins and it made some pretty good rum. I never reached those levels of ABV. I ran Rum and All Bran through the flute last Sunday. I will let you how much flavor did or did not come through in a couple of days.

... which is interesting, because in general it is thought that when distilling at/near azeotropic conditions, you turn pretty much everything into a neutral, no? That's pretty much how I understand others who run LM or VM's ... MR, LWTC, are we on to something, here?

Odin.

well I would have thought so but my flute will do a constant 90-94% with heavy flavor. Birdwatchers tasted like crap.

Going back to my original post. The recycle mechanics are likely the reason for most of the flavor carry over. Imposed reflux can create some as well but not as much. I would think that VM column's would carry flavor as well. A Boka LM is passive reflux where equilibrium is maintained.

My personal opinion is that CM's don't produce spirits in the same manner as LM's or VM's... With an LM I get the same compression of heads and tails, and rarely collect this small quantity of tails... But my hearts stay cleaner than I have heard about CM's producing... With my LM I get virtually flavorless neutral hearts unless I intentionally run fast which increases vapor temperature and lowers %ABV of the spirits collected... At some point I'd like to add a VM branch option onto my LM column to see the difference but experimenting with a true CM would be a ways down the road if at all...

CM's still get a bad rap Rad. I think the flute gone a long way to show there is value in the technique. Maybe some day we will convince you to build one. I would also like to see a combination of techniques used to create the perfect artisan still.
MR

[rad14701]

My personal opinion is that CM's don't produce spirits in the same manner as LM's or VM's... With an LM I get the same compression of heads and tails, and rarely collect this small quantity of tails... But my hearts stay cleaner than I have heard about CM's producing... With my LM I get virtually flavorless neutral hearts unless I intentionally run fast which increases vapor temperature and lowers %ABV of the spirits collected... At some point I'd like to add a VM branch option onto my LM column to see the difference but experimenting with a true CM would be a ways down the road if at all...

CM's still get a bad rap Rad. I think the flute gone a long way to show there is value in the technique. Maybe some day we will convince you to build one. I would also like to see a combination of techniques used to create the perfect artisan still.
MR

Perhaps a flute before any of the less popular designs, but you never know...

[kiwistiller]

Odin.
Kiwistiller and a few others (as I recall) have commented that their CM's make a very good white rum.

Absolutely.

... which is interesting, because in general it is thought that when distilling at/near azeotropic conditions, you turn pretty much everything into a neutral, no? That's pretty much how I understand others who run LM or VM's ... MR, LWTC, are we on to something, here?

Odin.

Not really what I was getting at... The best thing about a CM IMHO is that it suits low reflux operation as well as azeotropic. Hard to do that with an LM (how do you make sure you're still overflowing the reservoir with high takeoff and low reflux, especially as vapour production slows?? sight glass might help if that's your buzz I guess) or a VM (although constrictions or column height above the takeoff will help, with a constriction I got mine down to about 0.3:1 but I would be nervous constricting further)

I reckon white rum suits more reflux than other flavoured spirits. In fact, it's pretty much the only flavoured spirit I'd consider refluxing (for esterification purposes).

[Usge]

As the run wears on using a LM setup, even though you are taking off/returning the same ratio of condensed liquid...the amount of water in the vapor is continually increasing as the alc is taken off. The end result is the amount of reflux being applied for a given take off rate of liquid volume is effectively less (which is why you end up having to re-equalize or slow the take off rate towards end of run to maintain constant vapor/head temp and keep the abv constant/higher). For lower reflux operation using LM, I don't think it's entirely necessary to monitor your overflow since the reflux curve is obviously constantly changing as alc in the pot is depleted. I think it's more a matter of monitoring the abv of what you are taking off, head temp and adjust the valve accordingly as you go.

CM stills to me, work more like a "gate" that only allows certain vapor temp mixtures to pass. The amount of cool reflux being applied via a constant water flow CM reflux condenser is actually increasing as the alc is depleted ...to the point that eventually no vapor will pass through it. It's returning more as condensed reflux than it's passing through. It literally squeezes the shit out of it all the way down to the last bit. ...which is exactly what you are seeing. Happens the same way on VM stills as well from what I understand. To mimick the same behavior on an LM still, you'd have to continually reduce the take off rate as the alc was depleted. Anybody who's ever run a boka or other LM has experienced this towards the end of a run (ie., when temps start to go up, it's tails coming. Re-equalize and squeeze off a bit more). However, I'd also say...that running CM at lower rates, is no more a constant in terms of reflux than the LM is. You'd have to continually decrease the water flow and/or heat on a CM to actually be applying the "same" amount of reflux linearly as the alc in the pot was depleted. But, to Kiwi's point, I too agree it's probably the more flexible of the two in terms of lower abv runs...primarily because I also like to squeeze the tails side more...which happens automatically with CM, but takes quite a bit of monitoring and adjustment with an LM in that particular regard.

As to flavor influences...I've always believed/understood that lower alcs and higher alcs, and the compounds they might form with water/alc mixture...have certain recognizable characteristics...ie., acetone smells like acetone whether it came from a corn solution or apples. And these things going by temp...would produce certain flavor "generalities" if you will, for the duration of a run...with higher alcs bringing out certain characteristics as well...beyond the various fruit/grain influences on flavor. This was in fact the basis for my "Linear Flavor Theory" thread. I think there are a couple of things at play in this regard as to flavor influences. First, I'd say...that as far I can tell from my own experiments...the recipe you use or your ferment or still charge...certainly has a an influence. Certain things can become more, or less, pronounced at any given abv. I've had 80% runs that were clean with subtle flavor. I've had 93+% runs that were full of flavors (some not so pleasant). The point being....there are some compounds/mixtures that even in very small/tiny amounts...can have a very notable impact on flavor. And that means..even at 95%. I think this is also a part of it. Beyond all that, another contribution/difference in flavor would be the passing/condensing of vapor through larger volumes of liquid (ie., plates/thumpers, etc) at fixed column heights vs a longer tube with continuous smaller area mesh packing where mingling of vapor/reflux would happen somewhat more randomly area wise. As I mentioned before...the vapor speed/volume has a lot to do with this area.

Lastly, in terms of flavor....I think it "is" or has been sort of a common use of the term "reflux" to mean "less flavor", or even flavorless or neutral. But, in practice we all know it's really not that cut and dried, as anyone who's even distilled for a short length of time would have observed — ie that there are varying ratios of reflux that can be applied giving a wide variety of results. I think its also clearly understood through practice..that some of those congeners/esters just dont' give up real easy. Like Dnder said..there's a lot of different kinds of "vodka" all with their own bent/flavor profile.

Anyway, more noggin' scratching.

[mash rookie]

Well stated Usge. Several great points. Your flavor thread touched on many issues that apply to this discussion. Understanding on how a particular type of still affects the flavor congeners and then of course knowing what you are trying to get are going to be the big questions. My ultimate goal is to understand enough to build or modify a still that will suit several needs.

[Odin]

Usge,

Great how you describe CM works. I think you hit the bull's eye there!

Odin.