Why Copper Is Essential in Distilling

Why is Copper Used in Distilling?

When people think about distilling, they often think about beautiful copper stills, not realizing that copper is used in alcohol distilling for functional reasons, not just for its beauty.  While copper has an extremely high heat transfer rate- which can be both a blessing and a curse- it is copper’s reactivity that is the real reason copper has been used for distilling alcohol as far back as we can remember.

So, why use copper in distilling?  What benefits does it offer versus other materials, and are there any reasons to not just default to all-copper systems?

What Copper Does

During fermentation, when yeast converts sugars into alcohol, it also produces small amounts of other compounds.  One of these compounds is sulfur, often described as a ‘rotten egg’ smell.  This is a natural byproduct of fermentation, with some base ingredients producing more sulfur compounds than others.

Copper is a reactive metal.  One of the things it reacts with is sulfur compounds in the vapor during distillation, forming copper sulfide, which remains behind on the copper.  This essentially removes the sulfur compounds from the distillate, resulting in a finished spirit with a much cleaner aroma and smoother flavor.

Why an All-Copper Still is Not Needed

While the benefits of copper certainly outweigh its drawbacks, it is not necessary for the entire still to be made of copper.  It takes a surprisingly small amount of copper to react with the small amount of sulfur formed during fermentation.  For this reason it is very common, even in commercial distilling, to use stainless steel as the primary still material, with only the column, or even just the column packing or bubble plates, being made from copper.

Copper is considerably more expensive than stainless steel, and also requires more care and maintenance than stainless steel.  Copper is certainly beautiful, but from a purely functional standpoint, there are reasons to opt for a primarily stainless steel distiller.  Cost and maintenance are the primary two.

Will Copper Last Forever?

With proper care and maintenance a copper still will last for many years- virtually indefinitely.  However, the benefit of a stainless steel distiller with the addition of copper in the vapor path goes beyond cost.  For many home hobby distillers, using a relatively inexpensive copper packing such as copper mesh, copper spirals, or copper bubble plates, make replacing the copper a much less costly endeavor.

How to Care for Copper

As the copper reacts with sulfur compounds and forms copper sulfide, the copper will naturally darken and tarnish.  This shows that the copper is actually doing its job.  Without cleaning, the copper will lose its effectiveness, so it is important that you clean your copper parts to extend their useful life.

Cleaning is best done with a citric acid solution.  Vinegar can also be used, but is harsher, so it must be used more cautiously.

Citric Acid (Recommended)

Citric acid is generally the better choice because it:

• Removes oxidation (tarnish) very effectively.
• Is less aggressive than acetic acid (vinegar).
• Leaves less odor.
• Is less likely to etch the copper if not left too long.

Optimal mixture

• 30–50 grams of citric acid per liter of warm water
  • About 2–3 tablespoons per quart
  • About ½ cup per gallon

Warm water (100–120°F / 38–49°C) works much faster than cold.

Soak time

• Light tarnish: 5–10 minutes
• Heavy oxidation: 15–30 minutes

After soaking:

1. Scrub lightly with a soft nylon brush or Scotch-Brite (non-steel).
2. Rinse thoroughly with clean water.
3. Dry immediately.

For heavily oxidized bubble plates or packing, two shorter treatments are better than one long soak.

White Vinegar

Vinegar works, but because it’s acetic acid, it is somewhat harsher on copper if left for extended periods.

Optimal mixture

• 1 part distilled white vinegar
• 3 parts water

This produces approximately 1.25% acetic acid, which is strong enough for most cleaning.

For stubborn oxidation, many people use a 1:1 mixture, but I generally don’t recommend that for routine cleaning.

Soak time

• 10–20 minutes
• Avoid exceeding about 30 minutes

Again:

• Scrub lightly
• Rinse thoroughly
• Dry immediately

Some old recipes suggest adding salt to the vinegar mixture, as it accelerates cleaning.  I do not suggest adding salt to the mixture as it can increase corrosion and pitting if not rinsed extremely thoroughly.

The Bottom Line

Copper has earned its place in alcohol distillation for one very good reason- it works.  Its ability to remove sulfur compounds helps produce cleaner, smoother spirits.

However, it is also not necessary to go with an all-copper still for any functional reasons.  But, if you want that beautiful copper still to show off, there is no real reason not to go all-copper.

My personal recommendation after more than 30 years in the industry- go to our Moonshine Stills page and use the filters to help narrow your search to find your perfect still.