Do large scale Ethanol Extractors use copper condensers or just stainless steel?

I’ve built my own stills before and i know alot about their design and there is a reason why people use copper over stainless steel. Copper actually purifies the alcohol going thru it and im wondering if that is just not needed or specifically not wanted.
"The distillation is not only a simple process of separation, but the heat and the copper contact alter some of the flavour compounds, too. Heat promotes Maillard reactions producing furfural and sulphur compounds, especially thiophenes and polysulphides, which at low concentrations add a pleasant roasted and complex flavour, but produce pungent and unpleasant cereal and sulphury notes at high concentrations. Heat also promotes aldehyde reduction to alcohols and acids and their conversion further to esters. Lignin-derived components such as coumaric and ferulic acids can evolve to more spicy guiaicols. Acrolein (peppery) can form from bacterial fermentation products in presence heat. Fusel oils, 2-phenethanol (rose, flower) and furfurals (caramel, burnt sugar) are formed in pot-stills, but not significantly in column still distillations and therefore are likely to be generated by heat differences during distillation.

Copper removes most of the sulphury, cereal, feinty and meaty aromas during distillation. Especially the copper contact of the first wash still distillation is important. Total removal of copper contact in the spirit still has surprisingly minimal effect on the mentioned off-notes."

If you are stripping “beer” for high proof copper will be accepted. There are plenty of sulphur compounds that come for the ride while stripping. If you are building an evaporator to separate etoh and resin you will want stainless. It’s mostly the norm in pharmaceutical manafacrure, also more durable than copper.


I believe there are issues with THC + temperature + copper. But we do use copper to extract sulfur compounds from solution on occasion

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yea its def more durable and less work to maintain and im not saying the copper will help but will it hurt do u think?

It depends on what your building. Care to share and I’ll input my thoughts?

Im building a co2 expanded ethanol extractor so at some point im gonna need to strip the ethanol efficiently and im expecting alot of terpenes to be carried by the co2 so i could make one out of copper that better suits my needs then i could outta stainless but i would normally says you shouldnt use anything but stainless so im wondering if it was something lik future is saying where’s there’s actually a reaction. but at the same time is gonna be at partial vacuum so it prob wont be hot.

Copper salts are bad mkay. But stainless is just a way better option in my opinion. With stainless you don’t have to worry about 99% of reactions because they just won’t happen. With copper you could run into pH issues etc. Brass does react with terpenes, or at least hot terpenes and that is partially copper so take from that what you will.


@Photon_noir has explained to me the down sides to using copper with cannabinoids, but I can’t recall exactly the issue

yep, lik i said i normally say the same thing just curious of the exact reason was. knowing there’s even possibility is enough for me not to do it

If you need to prototype you could use copper. It’s quick and easy to fiddle with. I would not use it personally. The fact that side reactions may occur, copper salts may presist, and solder joints make it a less ideal choice. If your eager give it a go, there are lots of people dumping etoh through a washing machine. I refuse any of these practices, but they exist. So why not the copper?


The washing machine is definitely not GRAS


yea maybe, for the sake of argument im not distilling cannabinoids thru it just terpenes and ethanol. and i could redistil thru stainless steel. and all drinkable alcohol has touched a bunch of copper and there is no copper salt, salts only form after time and neglect

On the contrary, a copper still would be safe to distill etoh in. Especially if you need a still for alchol refinement. Copper shouldn’t be used in a processing vessel in that manner. Copper oxides could accumulate on surfaces, this could give your concentrate a nice statue of liberty green. Especially in the presence of co2 interacting with water in the etoh. You would be creating carbonic acid, this would attack the copper vessel. Do you need a vessel made? I employ a welder, you could message me for rates.


Copper has been used in cookware and even water pipes for a long time, and still today. However, copper can in some uncommon instances present a metal salt/corrosion problem in cannabis chemistry, such as in hydrocarbon vapor recovery from resin, in the presence of certain resin compounds, and water. It usually doesn’t react without water present, unless there are species present that are specifically reactive with copper, such as thiols and thioethers (sulfur compounds, like the ones often needed to be removed from concentrates, which makes copper a useful tool), alkylphosphines and other phosphorous compounds (some broken parts of the “gums”, for example), and pesticides which have all sorts of weird functional groups sticking out of them that copper likes, such as alkynes and cyanides (both are triple bond groups). Copper is a catalyst capable of single-electron transfers, which makes it willing to react and assist reactions as an intermediate, but catalysis would only change the stuff that touches the copper, and not the copper itself, so since we are worried about blue & green copper salts or organometallic complexes with the soft copper ligand it is more likely being “poisoned” or irreversibly reacted with things in the resin. Although copper can be used in coupling reactions with certain carboxylic acids, I do not think the cannabinoid acids are strong enough to react with copper, even with water present… that is to say, I have never seen or heard any reliable evidence to support this idea.

Ultimately, I believe it is some very “light” compound(s) that cause the problems when water is present. I deduce this from the facts that…
A. I have never had any problems with copper distillation column packing in dry or moist distillations; that is previously dehydrated and decarboxylated resin, nor even when the distilland was slightly wet at first, and
B. From the fact that the only place I have ever seen blue & green funky copper salt corrosion from resin was inside copper tubing in recovery pumps, upon which the operators were not utilizing filter driers… so the vapor being recovered contained moisture. This was a few years ago, before people knew better what they were doing.

Oh, and the one other place I have seen copper compounds that could have possibly contaminated my cannabis resin was in the puddle of faint blue cloudy water and fusel oils leftover in a rotovap after the initial distillation of brand-new bulk190 proof ethanol. Presumably this blue color was from copper oxide present in the enormous copper stills used to make the ethanol. So there is just one more reason to pre-distill your solvents at a temperature at least 20°C cooler than that at which it will be distilled from your cannabis resin before ever using said solvents to extract cannabis!


I used copper packing on my recovery still at 5gal scale.

Moved to copper column and condenser on my early keg based 15 gal still.

On both occasions that I tried recovering the last of the EtOH off the extracted plant material by distillation, the alcohol I got back was vividly blue. My assumption was Copper Sulphate. With the Sulphur presumably coming from proteins in the plant material (amino acids Methionine & Cystine).

So my vote would also be to stick with stainless.

Probably should have tried the GRAUS cannabis disorienter Supercritical420 & Future have been using. Washing Machine "Salad Spinner" tek

Couldn’t convince myself the wetted path was appropriate for Meds, couldn’t squeeze R&D funds to solve that from the ground up.

It never occurred to me to JUST use it for recovering the last bit of solvent. :thinking:

Looks like the CUP 15 has been ordered…

Yea, copper’s wide but limited reactivity is why it’s used spirit distillation, many conjures thats arent sulfer based are known to be affected by copper at least to a small degree. I just figured that very few cannabinoids will be volatile enough to make it over and almost all the terpenes in cannabis are found is another plant that has been distilled with copper condensers.

Any acidity will corrode copper, acid vapors can Co distill with etoh. Terpines on their own have no ph, due to non polar nature. When emulsifyed with water, or traces of water in etoh it can modify the ph. Try to test the pH of a hydrosol vs the separated oil. It proves the theory. Before you do the build get some copper and immerse it into a solution that will simulate operating. Get some copper test strips meant for aquarium use to test. Share the findings with us.


i dont use water so its not really hydrosol right? the only acid they would be exposed to is the ethanolic carbonic acid but that should be almost entirely dissipated by this point, i wouldnt be able to pull a vacuum if there was any co2 left in solution, but i will try measuring the ph next time with universal strips

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So what if I have a still for reclaiming ethanol that’s all stainless steel except for the condensing coils those are copper. My builder is trying to say the stil would be 20x slower with stainless coils. Could I get some help on the subject?

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