Using reflux to encourage Fischer Esterification

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Using reflux to encourage Fischer Esterification

Post by Single Malt Yinzer » Fri Dec 15, 2017 11:27 am

https://www.youtube.com/watch?v=lolclWtn0Xk" onclick="window.open(this.href);return false;" rel="nofollow

http://homedistiller.org/wiki/index.php ... rification" onclick="window.open(this.href);return false;" rel="nofollow

So I found it interesting that in the video they use sulphuric acid as a catalyst. They then heat the material and use reflux to condense it back into a liquid. Apparently Der Wo was on to these tricks already.

Translated: If you use reflux it is also encouraging esters (flavor compounds) to form.

Also: Come back Der Wo!

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Re: Using reflux to encourage Fischer Esterification

Post by LWTCS » Fri Dec 15, 2017 11:36 am

Yes this is exactly why protracted 100% reflux periods ( coupled with entrainment) to drive up / enrich abv on the plates of a short plated column do not always translate to "clean" product when producing vodka. Much better off with a higher plate count and less reflux if your trying to produce a more true/ optimal azeotropic neutral.

With rums a simple 100% reflux period (prolonging exposure to heat) will absolutely promote esterification. No catalyst needed.

Nice post.
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Re: Using reflux to encourage Fischer Esterification

Post by zapata » Fri Dec 15, 2017 5:03 pm

+2 for derwo!

I've got a lab glass setup Im playing with. Not specifically doing the Fischer reaction, right now just "aging". I can easily let it reflux for extended periods. I nuked some UJ to get the oak compounds in, and am now refluxing away (off oak) whenever convenient. Hoping for some esterification, specifically transesterification amongst other reactions, but not forcing it with h2so4 because I'm not going to redistill, just drink boiler contents when finished.

There is a general rule of thumb in chemistry that for every 10*C increase in temperature, chemical reactions increase 2x in speed. Roughly estimated, under reflux it should "age" about 64x faster than bourbon (about another 2x faster for scotch due to lower avg temps in scotland's rickhouses) That still means about 6 days of refluxing to approximate a year in Kentucky. But we'll see after it's accumulated a few "years" of age. It gets some air in between reflux sessions, but I also plan to repeat under slight positive pressure with pure O2 (balloon over vent) just to see. (Just in case this sounds scary, its not uncommon in chem labs I have worked in).

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Re: Using reflux to encourage Fischer Esterification

Post by DAD300 » Mon Dec 18, 2017 9:45 am

Longer heatup times will cause more esterfication also. Just because you can get from ambient to 170F in 45 minutes, doesn't mean you should. You're not saving power either way just getting more flavor.

And if you extend the time in the boiler while heating, there are more components at play than if refluxing in the column.

If your norm is to heatup as fast as you can, try cutting it back and taking 50% longer. You'll get a lot more flavors.
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Re: Using reflux to encourage Fischer Esterification

Post by NZChris » Mon Dec 18, 2017 10:29 am

One of the advantages of having a preheater is that the next still charge is hot and refluxing for a long time before it goes into the main boiler, meaning I only have to hold back the first drips for the first run.

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Re: Using reflux to encourage Fischer Esterification

Post by WIski » Mon Dec 18, 2017 12:02 pm

Yes, I also like to stew some feints or higher abv keep with backset to add to the boiler charge. Then slow heat up. Unscientifically I believe this brings more flavor. YMMV

Also totally agree OtisT and Kareltje. :thumbup:

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Re: Using reflux to encourage Fischer Esterification

Post by Single Malt Yinzer » Mon Dec 18, 2017 12:35 pm

https://www.bostonapothecary.com/from-f ... de-simple/" onclick="window.open(this.href);return false;" rel="nofollow

Reading this I found one item really interesting:
I suspect the the fractions are relocated to a part of the column where alcohol is particularly high favoring ester formation over ester break up. Where alcohol is particularly high there is little water to break up the esters.
Did we think about: Esters may form more frequently in vapor or on a plate/packing material. Would more headspace encourage more ester production? I know that many Scottish pot distillers* leave a lot of headspace in their stills. The idea I've read about it is about copper contact cleaning Sulphuric compounds out of the vapor, but maybe that's not it, it's unknowingly about esters.

*(from the book- Peat Smoke and Spirit: The Story of Islay and Its Whiskies)

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Re: Using reflux to encourage Fischer Esterification

Post by OtisT » Mon Dec 18, 2017 3:04 pm

DAD300 wrote:Longer heatup times will cause more esterfication also. Just because you can get from ambient to 170F in 45 minutes, doesn't mean you should. You're not saving power either way just getting more flavor.

And if you extend the time in the boiler while heating, there are more components at play than if refluxing in the column.

If your norm is to heatup as fast as you can, try cutting it back and taking 50% longer. You'll get a lot more flavors.
Damn, this thread good. :-). I know there has been talk of esterfication in the boiler, questions really as to whether it is taking place there or not, but this is the first I recall reading where someone confirms it from their own experience. Considering it was someone as experienced as DAD, I will believe it until someone proves otherwise. ;-). So much for fast strips.

So DAD, what part are you saying to slow down? Just the heat up to boil, leaving under full reflux for a period before stripping, or do you keep the entire run under some reflux?

I know this was one of our questions to that scientist Simgle Malt Yantzer interviewed. Will have to listen to that to see what he thought on this subject.

Thanks DAD300. On my next big ferment I’ll try one fast and one slow, to see if I am able to tell a difference in my low wines.

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Re: Using reflux to encourage Fischer Esterification

Post by DAD300 » Tue Dec 19, 2017 9:54 am

In the name of increased flavor, I'm only slowing heatup to increase flavor. But I'm making sure the still charge is acidic (dunder), making slightly wider cuts and using acidic fruit (dried cherry) during aging. It's not one thing making a big dif, it's a combo of little things.

It took me a long time to buy off on dunder. Try it.

A fast strip may be alright if you've slowed the heatup. But fast strip implies second or spirit run. That implies another opportunity to loose or increase flavor.
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Re: Using reflux to encourage Fischer Esterification

Post by Kareltje » Tue Dec 19, 2017 1:26 pm

DAD300 wrote: A fast strip may be alright if you've slowed the heatup. But fast strip implies second or spirit run. That implies another opportunity to loose or increase flavor.
Funny. Because most heat up fast and maybe slow down during the first part of the run. You suggest the opposite.

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Re: Using reflux to encourage Fischer Esterification

Post by OtisT » Tue Dec 19, 2017 10:29 pm

DAD300 wrote:It took me a long time to buy off on dunder. Try it.

A fast strip may be alright if you've slowed the heatup. But fast strip implies second or spirit run.
Thanks DAD. Yes, I am on the Dunder train already, and I am a big advocate of it. All summer and fall I have been using Dunder/Backset mixed with feints from the previous run in my spirit runs. In most cases, I also dilute the wash with fresh ferment as well. I can tell the difference in my product for sure. I currently have infected Dunder and infected Backset for my next rum and bourbon. Yummy.

Yes, my current protocol for most everything is a Strip and Spirit Run. I have done one small rum distillation in one run, and plan to try more of that again in the spring. It was a small batch and it required a conservative cut, but it tasted great and I personally thought it was cool having color come through in my product. I’m still learning a lot, and am having fun experimenting. :-)

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Re: Using reflux to encourage Fischer Esterification

Post by DAD300 » Wed Dec 20, 2017 9:10 pm

If your heatup is slowed you have the most exposure and time with all the elements to increase the esterfication. Once the vapor is in the column, a lot of the simple components are missing.

I go from 10% ferment to ~80% in one run.

But if I were doing strip and spirit runs, think about adding dunder in the strip and spirit run. Hmmm...
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Re: Using reflux to encourage Fischer Esterification

Post by HDNB » Thu Dec 21, 2017 7:10 am

so how long is this piece of string? My steam jacket takes about 2.5 hours to come on line and i usually reflux the fores cut at a slooow dribble for an hour.
is that considered a slow heat up?

at least i'm feeling better about it now, reading this thread.

i had a sip of jefferson's top shelf bourbon yesterday out in thee still shack. really nice...as i was sitting there about 5 feet from the fores collection, it seemed to me that it had a palate not unlike what my fores pail smells like... juicy fruit gum. interesting.
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Re: Using reflux to encourage Fischer Esterification

Post by OtisT » Thu Dec 21, 2017 9:41 am

DAD300 wrote:If your heatup is slowed you have the most exposure and time with all the elements to increase the esterfication. Once the vapor is in the column, a lot of the simple components are missing.

I go from 10% ferment to ~80% in one run.

But if I were doing strip and spirit runs, think about adding dunder in the strip and spirit run. Hmmm...
Thanks for the good advice. Two posts back you mentioned making the still charge acidic for esterfication conditions. Is there a target PH you shoot for? Here is why I ask.....

I forgot to mention that I also use dunder/backset in my ferment. At the beginning of my ferment I adjust the PH to account for the backset/dunder, but of course it becomes more acidic as it ferments. I guess I can always add more dunder to the charge at the cost of ABV, but would only do so if doing a strip/spirit run. Either that, or just add some acid, especially if I am shooting for a single run.

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Re: Using reflux to encourage Fischer Esterification

Post by DAD300 » Thu Dec 21, 2017 9:49 pm

You can add dunder or backset as you fill the boiler for a distillation. Nasty dunder added just before distillation will lower ph and add all kinds of components and acids during heatup.

My heatup on two dif stills takes 90 minutes But I've started slowing it to 120 minutes.

I had a hard time buying into the adding dunder to the charge before distillation, till I tried it.
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Re: Using reflux to encourage Fischer Esterification

Post by MDH » Thu Dec 21, 2017 11:19 pm

I like the thought but the problem with this idea is that you are going to be proofing to 60-70% and barrel aging it. Barrels impart their own acids and other things the spirit reacts with. In other words, you are going to still be aging this for a long time anyway, so why bother with the additional distillation effort?
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Re: Using reflux to encourage Fischer Esterification

Post by DAD300 » Thu Dec 21, 2017 11:42 pm

Why bother? Hmmmm...
More, better, flavor, quicker, whether new white, aged or barreled!
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Re: Using reflux to encourage Fischer Esterification

Post by zapata » Fri Dec 22, 2017 12:23 am

I havent seen it documented because we tend to focus on acids in dunder, but it should also be relatively rich in higher alcohols. These alcohols can become tasty esters a barrel and time can't really contribute.

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Re: Using reflux to encourage Fischer Esterification

Post by NZChris » Fri Dec 22, 2017 12:57 am

MDH wrote:I like the thought but the problem with this idea is that you are going to be proofing to 60-70% and barrel aging it. Barrels impart their own acids and other things the spirit reacts with. In other words, you are going to still be aging this for a long time anyway, so why bother with the additional distillation effort?
There are more ways to do this than you might think and they're not much trouble or expense once you have set up for it.

My latest UJSSM wash sat in the preheater for several hours while I did a spirit run in the main boiler, then the low wines sat at 150F with an oak domino for 6 days before being run with the domino still in it. Unfortunately, I don't really have something I can use for a side but side comparison, but it is already pretty good for a week old white dog.

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Re: Using reflux to encourage Fischer Esterification

Post by der wo » Fri Dec 22, 2017 7:29 am

That you know, I am still alive... I don't want to post much, but here I will write something:

"With rums a simple 100% reflux period (prolonging exposure to heat) will absolutely promote esterification." Yes, esterification, but not the much much more effective Fischer-Speier-esterification. "No catalyst needed." Ever tried? Ever worked with butyric infected dunder like typical for some heavy Rums? You don't want ANY of this awful smell in your product. You want 100% esterification of butyric and similar ugly acids (formic and propionic for example). Imagine you are a producer for synthetical flavors, perhaps for sweets or soap, many of your products will be made from those acids. No way to sell a flavor with remaining traces of sweat or vomit smell. Try ONCE sulphuric acid and you will never look back. BTW, it's just boring normal tradition. Rum producers use sulphuric acid since a long time (without knowing what they do). HD is a century later than the industry in this case.
Yes, they also use 100% reflux and slowly heating up. But this is not the key to a complete esterification. Without catalyst it's a good tool, if it is not important to get everything esterified. It depends on the types of acids. For example a typical lactic infected grain wash from unboiled wort: Lactic acid smells nice. No need to turn every single acid molecule into an ester. Lactic acid and esters smell similar, but the esters much more intense. So here esterification brings out more of an already existing flavor, that's all. No turning a skunk into an strawberry here.
But perhaps 100% reflux or heating up slowly helps -even if you already have esterified all ugly smells using a catalyst- to promote further more complex esters. So perhaps the catalyst is no complete replacement for applying heat and time. For sure heat and time is a bad replacement for such a cheap and fast catalyst. I think 100% reflux or heating up slowly is an aging reactor (of course artificially aging produces the benefits of real age only partially).

For me the thread turned off-topic immediately after the OP. You are writing about esterification, not Fischer-Speier-esterification. For me, using 100% reflux without catalyst for esterification is similar like 100% reflux without packing for concentrating foreshots. Everyone with a packed column (or sulphuric acid) asks "Why?"

"making the still charge acidic for esterfication conditions. Is there a target PH you shoot for?" Here the same. Lowering the pH is knocking at a door, to use sulphuric acid is having the key. You can try it out very effortless: Mix ethanol with vinegar. How will it smell? Like Ethanol and vinegar. Then stir into some citric acid. How will it smell? Still like ethanol and vinegar. Now add one drop sulphuric acid and it will immediately change it's flavor. It's not because sulphuric is much more acidic than citric, it's simply because sulphuric works as a catalyst and citric not.

You results may vary of course. Also I haven't worked enough in this direction to be aware of all facettes of using sulphuric acid. But in general perhaps you can agree, that here is something more than "no, not needed, my spirits are all fine without".

Happy new year, der wo
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Re: Using reflux to encourage Fischer Esterification

Post by HDNB » Fri Dec 22, 2017 8:01 am

Der, can you point to a sulfuric acid for esterfication research? .... for a recipe? are we talking 1 drop per hundred litres of wash, or one drop per hundred litres of low wines? much more, or less?
immediately before distilling, or give it time to work? a day, two?

it's something i'd like to try but some professional direction would be awesome.
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Re: Using reflux to encourage Fischer Esterification

Post by OtisT » Fri Dec 22, 2017 9:13 am

der wo wrote:That you know, I am still alive...
Thanks Der Wo for the sage wisdom, and I am glad to hear you are still kickin. :-)

OK. I’ll be buying some sulfuric acid to experiment with. I’ve read your previous posts on it, but my previous casual search for that acid did not pan out. I guess I will look harder or go to the Google to find some. I love this freakin hobby. :-)

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Re: Using reflux to encourage Fischer Esterification

Post by NZChris » Fri Dec 22, 2017 10:14 am

Nice to see you around, der Wu. I used to use sulfuric acid in rum when I first started, but didn't bother when I restarted making it a few years ago. My next project is rum, so I'll start using it again to see if it makes a difference.
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Using reflux to encourage Fischer Esterification

Post by Badmotivator » Fri Dec 22, 2017 11:26 am

Da ist Der Wo!

I did a big panela-plus-muck rum project this year. The A/B tests between the straight ferment and the super-infected ferment were unambiguous; long reflux can create a ton of esters. But now I am regretting that I did not also try one distillation with sulphuric acid as a catalyst. Schade.

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Re: Using reflux to encourage Fischer Esterification

Post by Single Malt Yinzer » Fri Dec 22, 2017 6:03 pm

So we're covering multiple aspects of this. To clarify:
1. Lowering the pH speeds up ester formation. Sulphuric acid is a really strong acid and really moves things along.
2. Increased heat speeds up ester formation. The longer the wash is heated the more esters form.
3. Esters do form in barrels during aging, but at a lower rate than in #2. Tannins from the wood cause #1.
der wo wrote:That you know, I am still alive...
:thumbup: Glad to see you around buddy. I figured one of my ester posts would get you back to posting again.
der wo wrote:You are writing about esterification, not Fischer-Speier-esterification. For me, using 100% reflux without catalyst for esterification is similar like 100% reflux without packing for concentrating foreshots. Everyone with a packed column (or sulphuric acid) asks "Why?"
Two things:
1) (For Der Wo) While there are several type of esterification, the two major ones distiller deal with are enzymatic processes during fermentation and Fischer esterification during fermentation, distilling and aging. I admit I could be missing something, there's a lot about this stuff I don't know about.
2) (Not for Der Wo) While sulfuric is the best acid for this it isn't the only one that works. Nearly any acid can be the catalyst. This is why it works despite not having sulfuric in the wash. After fermentation there are other acids in the wash. A bacterial infection with lacto works to help increase those acids and lower pH. Dunder/backset the same. Using Der Wo's example think of the acid as the packing material in a column. There's a lot of different packing materials available, but sulfuric is the best.

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Re: Using reflux to encourage Fischer Esterification

Post by RedwoodHillBilly » Sat Dec 23, 2017 6:55 am

OtisT wrote:
der wo wrote:That you know, I am still alive...
Thanks Der Wo for the sage wisdom, and I am glad to hear you are still kickin. :-)

OK. I’ll be buying some sulfuric acid to experiment with. I’ve read your previous posts on it, but my previous casual search for that acid did not pan out. I guess I will look harder or go to the Google to find some. I love this freakin hobby. :-)

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Re: Using reflux to encourage Fischer Esterification

Post by der wo » Sat Dec 23, 2017 7:15 am

HDNB,
The pH of Rum dunder is set to 5.5 with calcium hydroxide and sulphuric acid. This is the traditional way. Because normally Rum producers, who use dunder, add it before fermentation, perhaps we should use it before fermentation too? I am not sure. My experiment in the "Pure acids and esters production"-thread showed, that the esters are very volatile and air out very fast. I fear, most of them will leave through the airlock during fermentation. But on the other hand my experiment in "My infected Rum"-thread showed, that if we esterify all acids using the catalyst, we get easily a massive amount of them, we don't need much infected dunder, and perhaps it's not such bad to loose many of them through the airlock. In infected dunder is much more ester potential (acids content) than I thought.

The most obvious effect you will have by adding dunder and sulphuric acid to low wines, because of the high abv. So perhaps start there. Or add it to the dry wash just before stripping. One run with and another without. So you have something to compare.
Interesting would be an experiment without infections too. Just a normal grain wash, one half with added sulphuric just before stripping, the other without, comparing the low wines. Don't expect a such strong difference like with infections. But you will see, what ester potential your ferment has.

Sulphuric acid is a catalyst here, what means it is the same game like with enzymes and starch conversion: The amount is not important in theory. But in practice perhaps it's better the more you have. But I don't know, what side-effects a very high amount could have. So I would try moderate amounts. I think: 10ml sulphuric acid (or 30ml battery acid) per 10l low wines or wash. I don't think it needs much time. The heat up phase will equal a few days waiting time. Add it just before distilling or for example if you want to compare the flavor of one low wines container with sulphuric against another one without before distilling, add it one day before distilling.

Research: Wikipedia has an article about Fischer-speier-esterification. And look here on hd for the pdfs: Arroyo, "the production of heavy bodied Rum" and "Production of heavy Rums"


SMY,
"Lowering the pH speeds up ester formation. Sulphuric acid is a really strong acid and really moves things along." Not because of its acidity. You can use small amounts in a highly buffered wash, so it will not affect much the pH but it will affect the esterification. I am not sure, but from my small experience I think that the effect of sulphuric acid is independent from the pH change (which can vary a lot in dependence of the buffer capacity).
"and Fischer esterification during fermentation, distilling and aging." Fischer esterification during aging? That would mean adding sulphuric acid or other similar effective catalysts to the new make. But ok, I don't know where exactly "normal" esterification ends and Fischer starts by definition. Does it need a strong catalyst and heating up and reflux it to name it Fischer by definition? I don't know. For me it sounds wrong to name it Fischer without adding a strong catalyst.
"Using Der Wo's example think of the acid as the packing material in a column. There's a lot of different packing materials available, but sulfuric is the best." If you want to know, if the difference is really only like scrubbies vs SPP, you have to try it.


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Re: Using reflux to encourage Fischer Esterification

Post by RedwoodHillBilly » Sat Dec 23, 2017 7:18 am

SMY, The reason that concentrated H2SO4 is a good catalyst is that it is a "drying acid" i.e. it is very hygroscopic. Remember that Fischer esterification is a reversible reaction. By sequestering H2O from the reaction site, you encourage the forward reaction and discourage the reverse reaction. Not that other acids or dilute H2SO4 won't work, but they will be less efficient.
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Re: Using reflux to encourage Fischer Esterification

Post by zapata » Sat Dec 23, 2017 7:36 am

The wikipedia entry sums up several of these points well.
https://en.m.wikipedia.org/wiki/Fischer ... rification" onclick="window.open(this.href);return false;" rel="nofollow
The natural esterification that takes place in wines and other alcoholic beverages during the aging process is an example of acid-catalysed esterification. Over time, the acidity of the acetic acid and tannins in an aging wine will catalytically protonate other organic acids (including acetic acid itself), encouraging ethanol to react as a nucleophile. As a result, ethyl acetate—the ester of ethanol and acetic acid—is the most abundant ester in wines. Other combinations of organic alcohols (such as phenol-containing compounds) and organic acids lead to a variety of different esters in wines, contributing to their different flavours, smells and tastes. Of course, when compared to sulfuric acid conditions, the acid conditions in a wine are mild, so yield is low (often in tenths or hundredths of a percentage point by volume) and take years for ester to accumulate.
As to whether the non-sulphuric catalyzed esterifications are technically Fischer-Speier, the ester entry says this
The classic synthesis is the Fischer esterification, which involves treating a carboxylic acid with an alcohol in the presence of a dehydrating agent
So sounds like no dehydrating agent means not a Fischer, just a "normal" esterification.

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NZChris
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Re: Using reflux to encourage Fischer Esterification

Post by NZChris » Sat Dec 23, 2017 6:56 pm

Sulfuric acid in low wines is also likely to make you some diethyl ether, which forms an azeotrope with ethanol and comes over in the distillation. I'm not sure this is desirable and I won't be trying it until I know more about it. I get silly enough on rum already without adding ether to the mix of volatiles in it.

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