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Copper Good Ascending...Copper Bad Descending

edited January 2015 in General

Just got started reading Whiskey Science and I got to the following...
Saturday, October 18, 2014 Copper

Ethyl carbamate (EC, urethane) was a hot topic in the 1980s, as it was found to be carcinogenic and to increase during maturation phase of spirits. At the time various whiskies, especially grain or bourbon whiskies from stainless steel column stills were producing spirits with way too much EC and the concentrations seemed only to increase during maturation. It was found that copper in the ascending phase on still decreased EC dramatically and copper was (re)introduced into column stills. Adversely copper salts in the new make does catalyses the EC formation during the maturation, so most grain distillers use only stainless steel in the condensers to diminish the amount of copper residues in the new make.

Now, I also relate this to the idea that every once in a while someone produces Blue Distillate. The Blue has to come from copper sulphate in the descending path, vapor or liquid probably doesn't matter... but copper tubed liebigs...would matter. Those, like me, that believe a still cleans its self, would rarely bother to clean the descending path before a new run. I think we also live with the assumption that high ABV Ethanol and Copper do not react...this article says otherwise.

The production of ethyl carbamate has nothing to do with copper as a metal transferring into distillate. It has to do with ethanol and copper reacting to produce ethyl carbamate.

My rigs are all Stainless, but I have a ball of copper mesh in the column. It used to be at the bottom of the column, but that got hard to clean. So, lately it has been at the top just before the takeoff.

At the very least...clean the "descending" copper path just as you would the boiler before a run.

Best, think copper in ascending and Stainless only in descending path.

Standing by

DAD... not yours.. ah, hell... I don't know...


  • Been thinking along those lines for a while here at StillDragon.

    Maybe unrelated but licking /tasting a section of SS is very inert to the tongue. Copper on the otherhand taste terrible...

    This discussion could really create some heated debate at some other internet hang outs.

    StillDragon North America - Your StillDragon® Distributor for North America

  • The all copper cult is sure to be dispatching it's denizens.

  • even kothe has stainless in downward flow of vapor tubes and the condenser

  • edited January 2015

    As important than EC in the discussion is the level of free copper in the distillate, which is primarily due to copper contact in the condenser/condensate path.

    There are a number of interesting studies out of Brazil that discuss free copper in the distillate and mechanisms to control it. Apparently it is relatively easy to have copper levels well in excess of government regulated limits (where applicable).

    While this paper is more focused on removing free copper after distillation, it does contain a good overview of the problem in the introduction, and includes some interesting anecdotes on copper condenser cleaning and impact on copper levels.

    Removal of copper(II) from sugar-cane spirits employing chitosan

  • edited January 2015

    And this one as well:

    The role of distillation on the quality of tequila

    When distillations were done in copper alembics, however, it was found that the copper content of the rectified product exceeded the amount permitted in the official tequila standards.

  • Well, the moral high ground no longer exists! They are choosing to ignore the post...and the article!

    I must say I am dismayed. I have not had a copper condenser (RC or PC) for a long time, and I certainly will never now.

    But for those that have literally screamed at and banned people for plastic, aluminum, silicone and iron to ignore scientific fact is...


    DAD... not yours.. ah, hell... I don't know...

  • "They"?

    Could not find where you presented the info other than here dad?

    StillDragon North America - Your StillDragon® Distributor for North America

  • edited January 2015

    Ah ,,,found it.

    The " SS builder" comment comes from a "copper builder". No surprises there.

    We do recognize the benefit of copper on the ascending side,,,,,,hence the copper plate assemblies since day one.

    StillDragon North America - Your StillDragon® Distributor for North America

  • not sure if this fits the thread here but I went from all copper to the 4" dragon with standard bubble caps (copper). I did end up with the rotten egg sulphide smell, not in my distillate but in vapor. I thought about the peroxide solution but was able to cure my problems with a wad of copper at my last tee before the dephleg.

  • Good show Nightside.

    Wad of copper is certainly cost effective.

    StillDragon North America - Your StillDragon® Distributor for North America

  • Perfect...a wad of mesh anywhere on the vapor ascending side.

    DAD... not yours.. ah, hell... I don't know...

  • What about 'tinning the copper' for folks with old-school shotgun and liebig condensers?

  • It sounds like an improvement, but you could build a SS Leibig easier than tin one.

    My current Product Condenser, SD Shotgun, is SS...but I built several SS Product Condensers (dimroth) from keg spears and a SS keg spear covered with PVC shell worked perfect for years.

    DAD... not yours.. ah, hell... I don't know...

  • I run a ss rig that I built. Recently someone gave me a link to Holstein that showed they use a copper catalyzer on their rigs. Figured if they use extra copper then why not? So I built a packed section and filled it with cut 1/2 inch copper pipe. Haven't run it yet but will put it above the RC. I also put a couple wads of packing below the first plate...

  • I have seen a few references to a fix for the ethyl carbamate problem by double distilling. I don't really want to get rid of my copper condensers, so is there a practical fix.

    How big an issue is this and is there a recomended way to use copper in the downwards path and avoid the problem?

  • Dad are you sure about that comment regarding ethyl carbamate being produced by copper reacting with ethanol?

    Either hydrocyanic acid or urea can react with ethanol to form it, but these are typically produced during the fermentation process.

    Did I just get "hooked"?

  • edited January 2015

    The three "Formation of" papers in this link are the great reads.

    Especially "Part 3" - because that one nails it. There are multiple pathways for EC formation, and numerous precursors - these are influenced by more than just still construction, even down to the particular strain and quantity of malt used, or whether fruit stone is included in the fermentation. To make things more complex, there are precursors to EC that may form EC during aging, and are not found as EC in new make spirit. I believe all of these factors made the initial studies somewhat confusing, since many appeared to be contradictory.

    Double distillation will significantly reduce EC, slower distillation (more gentle heating) will reduce EC, using low EC-precursor malts will reduce EC, taking the pits out of Fruit will reduce EC, "stainless down" will reduce EC. There has been some discussion that higher reflux ratios will reduce EC in systems that use "stainless down".

    If you are completely bored, snowed in, stuck in an airport, in jail. Take all those papers, print them out, and read them in order of the date of publication. What you'll find is that there is an evolution of knowledge about EC, since there was a major push in research in the late 80s, early 90s. The early papers have a bit of conjecture, are simplistic, and the later papers seem to nail it. However, if you read them all out of order, or selectively pick one or two, you get a very confusing picture.

    I can't seem to find the specific study that made the recommendation, but diligent cleaning of the copper condenser was found to reduce EC as well, it was one of the Cachaca papers. It likely has to do with the level of copper in the distillate, allowing for greater EC formation post distillation.

  • Ok you got me thinking. Went and looked at Holstein and their patent for the copper catalyst. They put it above the dephlegmator and it should be obvious enough. Enough copper to get rid of the problem, positioned so that any nasties return to the boiler, and it shouldn't matter if you use copper condensers. Perhaps an extra copper catalyst before the high point in the vapour path wouldn't hurt in any still.

  • edited January 2015

    @Myles - It is exactly the reason we asked the SD crew to build the 12" crystal dragon this way. The glass section above the dephlegmator is to house an additional copper catalyst:

  • That is one fancy rig. Just love the look of that reducer.

  • Thanks for the links grim...

    No intention to hook any one...I won't kid about my booze.

    I'm even going through the science behind copper cooking pan demise. While they worry most about copper surfaces adding actual metal to our diet, they also mention the ethyl carbamate from oils burning on the surface.

    My column has copper mesh is on top to make it easier to clean, but my idea is to put it in the bottom of the column, in a "T".

    While I don't see this as bad as Tickle delivering high ABV in ole' milk juggs, it is a punch in the gut.

    DAD... not yours.. ah, hell... I don't know...

  • Trying to get my head round this. I think if you already have the precursors in the wash as fementation products then the copper acts as a catalyst to produce the carbamate. Thus it makes sense to add enough copper to get rid of it so that it returns to the boiler.

    Holstein put in 2 catalysts. One under and 1 over the dephlegmator. I have always had some copper mesh in my packed columns inside the keg connector, under the packing so to me having some as suggested by dad makes sense.

    Adding in another batch in the vapour path before a high point is also easy.

  • Myles you are spot-on. That's why you'll find there's a specialty malt barley grain JUST for the professional distillers. Lowest in the precursors to EC.

  • how about a copper tube 'wind chime' hanging in the boiler headspace?

  • I love wind chimes...

    DAD... not yours.. ah, hell... I don't know...

  • Time for me once again to parade my general ignorance before the public.

    This is a "for what its worth" posting. I came across this title on the interweb.

    Transition Metal Catalysis in Aerobic Alcohol Oxidation

    by Francesca Cardona and Camilla Parmeggiani

    English | 2014 | ISBN: 1849738238 | 304 pages | PDF | 17,8 MB

    This is what it's about:

    The oxidation of primary and secondary alcohols to the corresponding carbonyl compounds is of fundamental importance in organic synthesis, due to the wide use of these products as precursors and intermediates for many drugs, vitamins and fragrances. However, traditional oxidants are often toxic and release considerable amounts of by-products. As an alternative, oxygen is among the cheaper and less polluting stoichiometric oxidants, and the implementation of a transition metal-based catalyst in combination with oxygen represents an emerging alternative to the traditional procedures.

    This book aims to give an overview of the aerobic oxidation of alcohols catalyzed by transition metals, and covers the most important advances in the last fifteen years. Following an introductory chapter on homogeneous-, heterogeneous- and nano-catalysis, use of copper, ruthenium, palladium, gold, vanadium and iron are discussed in turn. The book concludes with a useful overview that includes representative experimental procedures.

    This book will provide a valuable reference to organic chemists and green chemists in academia and industry.

    For the life of me I'm not even sure the above descriptor relates to the subject under discussion here . . . . . . . maybe I ought to pass it on for others to flick through.

  • Lucky...this is about my position.

    If it says copper bad, I get it. What that says to me is, "I need a loving lab rat to translate!"

    DAD... not yours.. ah, hell... I don't know...

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