Pot still head configuration with alambic onion

[PalCabral]

Hiya distillers.

Modular stills have a great advantage with that they allow the distiller to change the configuration of the still depending on needs and whims. The column can easily be made taller or shorter, coldfingers and reflux condensers can be fitted or removed, plates and bubblers can be added. etc. with the use of tri clamp connections. The still can grow with the owner's ambitions and love for the hobby. The fact that I could from one run to another switch from pot still to reflux still by exchanging one or two modules is why I decided to buy one of these stills. For anyone looking for a still, to buy or build, this type is the one I recommend. I am writing this because the content of this thread is based around having the luxury of a modular still.

Copper pot still head expansion chambers, so called onion heads or copper helmets, are classic features in old style pot stills. There are different views on how much added value they provide compared with a column riser in pot still mode, but they do increase the vapor to copper interaction thus "cleaning up" the alcohol somewhat and they provide some passive reflux refining the vapors exiting the onion/helmet, raising the ABV of the ethanol coming out of the PC somewhat. I am not proposing that onion heads will make a huge difference in pot still mode but they will make some difference and they look absolutely fantastic. It's the classic look of a pot still/alambique/alambic and I have always had the ambition to get me one for my still.

Last week my copper onion head arrived and I have spent the last days cleaning it, running the vinegar, steam and sacrificial runs. Now I am ready for the fun part: including it in my rig. With several modules available to me, I can chose between different configurations. There are two that I especially are looking at and I wanted to bounce these, plus one more, with you to hear your thoughts about them.

This has been my current set up in Pot Still mode. A 15cm (6") 4-to-2 inch reducer (missing in the picture), connected to a 45cm (18") long 2" copper spool and then the elbow to the PC. Its' total height is 70cm (27.5") from boiler to top of elbow. The copper spool is the only module in my set up that is made from copper.

The copper onion head is 30cm x 30cm in size with a volume of 12L, connected via 4" tri clamp ferrules on each side. I've also added a 4" spool of 15cm (6") to connect the boiler with the onion.

Here are my thoughts how to configure the pot still head.

1. My first choice is a "swan's neck" configuration: the 15cm 4-to-2 inch reducer connecting the onion with the elbow that goes to the PC. Overall height from boiler to elbow is 70cm (27.5"), the same as in my current set up. This config should work well both for stripping runs as well as spirit runs. I am expecting a lot of flavors to be passed over but the onion head in tandem with careful control of the heat source will help in separation of the fractions during the spirit run, especially in the first half of the distillation.

2. My second choice is a "long neck" configuration, a wee bit inspired by my Scottish ancestors' whisky pot stills: the 15cm 4-to-2 inch reducer connecting to the 45cm (18") copper column before the elbow to the PC. All in all a height of 115cm (45") from boiler to elbow. To be honest I am not expecting a huge difference from the first configuration and I am only thinking of using it when running spirit runs. When running slow in a spirit run I could perhaps get a tad more passive reflux and higher proof compared to the no.1 config. I am thinking this could be a set up to use for Rums and Whiskeys where I want a slightly "lighter" flavor profile. However, maybe the biggest benefit of this configuration will be the added copper contact to the vapors? The disadvantage is that the tower gets so tall and I need to stand on a chair to mount the top modules...

What do you guys think? Am I overthinking it (again)? I am not taking it so serious myself either but I would like to hear your feedback.

On top of that, I am toying with two more ideas. As I'm not entirely sure what to expect in terms of separation vs smearing, and I do know the smearing increases with stills using onions as the distillation goes on (because the passive reflux is getting less and less efficient as the dome gets hotter), I have been thinking of adding my reflux condenser to the "swan's neck" to help cool the head down a little. Not going full reflux, more like how some of the Scottish Whisky stills have neck cooling to slow the vapor flow a bit.

I've also thought just having a short stub neck, dropping the reducer altogether, and lead the vapors straight to the PC. This would primarily be a configuration for stripping runs. But I learned from Alan Bishop that having too small of an outlet from the expansion chamber could put too much pressure on the top of the onion, ultimately breaking it. In my case, I'm more concerned the center of gravity get's out of whack and the whole thing looks like it could tip over any second.

There you have it. Options are fun challenges. I am running a spirit run tomorrow for my wheated Bourbon and I am thinking of baptizing the onion with it, using the first, swan's neck configuration. Wish me luck!

[Saltbush Bill]

The angle and cap on the end of that shotgun condenser still looks like they are creating a perfect pool to me.
Fixing that would be my priority.

[shadylane]

Copper pot still head expansion chambers, so called onion heads or copper helmets, are classic features in old style pot stills. There are different views on how much added value they provide compared with a column riser in pot still mode, but they do increase the vapor to copper interaction thus "cleaning up" the alcohol somewhat and they provide some passive reflux refining the vapors exiting the onion/helmet, raising the ABV of the ethanol coming out of the PC somewhat. I am not proposing that onion heads will make a huge difference in pot still mode but they will make some difference and they look absolutely fantastic. It's the classic look of a pot still/alambique/alambic and I have always had the ambition to get me one for my still.

I think onion heads have another advantage.
They slow down the vapor and allow droplets of liquid from the boiling pot to fall back down instead of riding the vapor up and out of the still so there's less smearing.

[jonnys_spirit]

I use my onion head on top of an 18"x3" riser with a sight-glass above that for pot still strips and spirit runs. The 2" shotgun points straight down with a and 3"-2" reducer and 90* elbow. I extend the 1/2" product condenser take-off a few feet away with a 45" copper elbow for collection into fractioning jars or into a carboy on a strip run.

For me, the riser>onion>sight-glass is very helpful for mitigating foaming during strips and preventing pukes. Otherwise it's mostly eye candy.

I do have plans to fabricate a vertical plate/thumper tube/downcomer so I can insert that plate between the riser and onion-head and run in a vertical thumper mode. Pretty sure that will have a measurable and meaningful impact on spirit runs.

Cheers,
jonny

[OtisT]

The angle and cap on the endbof that shotgun condenser still look like they are creating a perfect pool to me.
Fixing that would be my priority.

If he rotates the end cap 180 degrees, with the vent facing straight down, he would eliminate the pool by taking product from that side vent tub.

[PalCabral]

I use my onion head on top of an 18"x3" riser with a sight-glass above that for pot still strips and spirit runs. The 2" shotgun points straight down with a and 3"-2" reducer and 90* elbow. I extend the 1/2" product condenser take-off a few feet away with a 45" copper elbow for collection into fractioning jars or into a carboy on a strip run.

For me, the riser>onion>sight-glass is very helpful for mitigating foaming during strips and preventing pukes. Otherwise it's mostly eye candy.

I do have plans to fabricate a vertical plate/thumper tube/downcomer so I can insert that plate between the riser and onion-head and run in a vertical thumper mode. Pretty sure that will have a measurable and meaningful impact on spirit runs.

Cheers,
jonny

I am surprised you could get foaming/puking issues with the onion placement so high up?

I am sure the added plate will have a positive impact to your set up.

[PalCabral]

The angle and cap on the endbof that shotgun condenser still look like they are creating a perfect pool to me.
Fixing that would be my priority.

If he rotates the end cap 180 degrees, with the vent facing straight down, he would eliminate the pool by taking product from that side vent tub.

There would be a pool on my floor if I did that, which would really be a pooling problem

[PalCabral]

I think onion heads have another advantage.
They slow down the vapor and allow droplets of liquid from the boiling pot to fall back down instead of riding the vapor up and out of the still so there's less smearing.

This is what I am hoping for.

[PalCabral]

The angle and cap on the endbof that shotgun condenser still look like they are creating a perfect pool to me.
Fixing that would be my priority.

How should the angle of the vent be positioned, Bill? I do have a pool of 1cl trapped in the cap after distillation, so it's never concerned me and I never thought about what angle it should be.

[jonnys_spirit]

I use my onion head on top of an 18"x3" riser with a sight-glass above that for pot still strips and spirit runs. The 2" shotgun points straight down with a and 3"-2" reducer and 90* elbow. I extend the 1/2" product condenser take-off a few feet away with a 45" copper elbow for collection into fractioning jars or into a carboy on a strip run.

For me, the riser>onion>sight-glass is very helpful for mitigating foaming during strips and preventing pukes. Otherwise it's mostly eye candy.

I do have plans to fabricate a vertical plate/thumper tube/downcomer so I can insert that plate between the riser and onion-head and run in a vertical thumper mode. Pretty sure that will have a measurable and meaningful impact on spirit runs.

Cheers,
jonny

I am surprised you could get foaming/puking issues with the onion placement so high up?

I am sure the added plate will have a positive impact to your set up.

It's a 16g boiler and I don't leave much headroom on a strip run so it typically foams up a bit and can push past the riser and onion into the sight glass depending on what I'm running. I'll back off power and take off fores for 30-45min which then allows me to inch it back up to full power for the rest of the strip It doesn't foam on a spirit run

Cheers,
jb

[PalCabral]

It's a 16g boiler and I don't leave much headroom on a strip run so it typically foams up a bit and can push past the riser and onion into the sight glass depending on what I'm running. I'll back off power and take off fores for 30-45min which then allows me to inch it back up to full power for the rest of the strip It doesn't foam on a spirit run

Cheers,
jb

I was kind of hoping that the onion would be a get out of puking card but I guess not...

On a serious note, I've made a point so far not to fill beyond 2/3 of capacity, and generally I run just below 60%, so with a dollop of butter I've been spared from puking so far, and I want to keep it that way. I did think I could be a bit more brave now with the onion, given that the expansion chamber should, in theory, collapse the foam "head" but I guess there are no free lunches.

[jonnys_spirit]

It's a 16g boiler and I don't leave much headroom on a strip run so it typically foams up a bit and can push past the riser and onion into the sight glass depending on what I'm running. I'll back off power and take off fores for 30-45min which then allows me to inch it back up to full power for the rest of the strip It doesn't foam on a spirit run

Cheers,
jb

I was kind of hoping that the onion would be a get out of puking card but I guess not...

On a serious note, I've made a point so far not to fill beyond 2/3 of capacity, and generally I run just below 60%, so with a dollop of butter I've been spared from puking so far, and I want to keep it that way. I did think I could be a bit more brave now with the onion, given that the expansion chamber should, in theory, collapse the foam "head" but I guess there are no free lunches.

It def helps with puking so you can generally run it harder but at the beginning of a run it can still puke. I run with a couple/few inches of headspace from top of the boiler and it does help me use closer to full volume of the boiler. For that, it's worth it to me and it looks cool

Cheers,
jonny

[OtisT]

The angle and cap on the endbof that shotgun condenser still look like they are creating a perfect pool to me.
Fixing that would be my priority.

If he rotates the end cap 180 degrees, with the vent facing straight down, he would eliminate the pool by taking product from that side vent tub.

There would be a pool on my floor if I did that, which would really be a pooling problem

I don’t think we are connecting. I think if you loosen up the Tri-clamp (don’t remove it) on the end cap, twist the end cap of the shotgun so the vent is pointing down, not up, tighten he clamp, then put a jar under what was the vent. No more pool and no spill.

[PalCabral]

I don’t think we are connecting. I think if you loosen up the Tri-clamp (don’t remove it) on the end cap, twist the end cap of the shotgun so the vent is pointing down, not up, tighten he clamp, then put a jar under what was the vent. No more pool and no spill.

I think we were connecting, Otis. Or at least, I understood your point. Thank you for pointing out a very simple yet effective way of solving the "pool problem". I was joking in my response to you. Never mind. Sometimes, jokes dont play out

However, never really thought pooling in such a small space could be a problem, though. The cap contains 4-5cl/1.5oz tops, and only 1/3 of that would get trapped under the spigot, so 1,5cl. In a distilling parrot, 15 to 20cl is trapped. I can't really see, with my basic knowledge, why this would be a concern for me? Excessive smearing? I am obviously missing something much bigger to derail the purpose of my thread? Should I be running around with my hands waving in the air in panic - 1,5cl trapped in a pool under the level line of the spigot?

Sorry, Otis, that was me being passively aggressive, not aimed at you though. My daughter reminds me regularly it's a bad thing.

[Homebrewer11777]

I don't believe the rotation of the cap will fix the issue. I have same cap and believe what this will end up looking like is the vent tube being almost horizontal to the floor aimed directly at the onion. There will still be a pool in the cap.

I am dealing with this issue by adding an 8" spool after the first 90 degree elbow to get the PC further away from the still, and then swapping the 45 degree elbow for a second 90 degree elbow to get the PC vertical so no pooling issues from that cap. Happy with how it works in terms of lack of any pooling in the cap but don't really know if this is ideal configuration for running a pot still for making bourbon.

I haven't added the onion yet but am sure it is in my future cause it looks cool and there is sufficient backstory to BS a better explanation to my wfe

[PalCabral]

I am dealing with this issue by adding an 8" spool after the first 90 degree elbow to get the PC further away from the still, and then swapping the 45 degree elbow for a second 90 degree elbow to get the PC vertical so no pooling issues from that cap. Happy with how it works in terms of lack of any pooling in the cap but don't really know if this is ideal configuration for running a pot still for making bourbon.

I haven't added the onion yet but am sure it is in my future cause it looks cool and there is sufficient backstory to BS a better explanation to my wfe

I'm still not sure this is an issue, the cup fills with 1.5cl, that's like 1/2 oz. I still don't understand how that can be a smearing issue? My smallest jars for collection during a spirit run are 7 times that size. But my solution to fix it would be to add a short 45 degree elbow after the PC facing down and then put the cap at the end of it, spout pointing directly downwards. I need, and prefer, my PC in an angle away from the still. It's the most practical set up for me.

She's a beauty, the onion. Today, after the disastrous stripping run I had yesterday, I gave her a good bath in PBW. She's curvy, just the way I like it. I'll give her a week of vacation now while I try to rescue my soiled immersion element.

[Yummyrum]

Is the outside of it lacquered or is it raw copper ?
Just wondering how many times you can soak it in PBW before it starts looking yuk.

As for the cap , I agree that any smearing is a joke compared to the collection jar size and what a Pot still does anyway , and if it was a problem , take the bloody cap off .