THE WAY OF COPPER
The Choice of Copper in Plant Material Distillations. Between Aesthetics and Functional Metal.
THE WAY OF COPPER
Distilling with Copper Stills, between Aesthetics & Functional Metal
It has long been known that copper is antimicrobial and has been used throughout history to purify water. There is evidence that it has been used as a biocide for over 4000 years (Gabbay 2009).
There is a plethora of information on the antimicrobial effects of copper. In one study, it was shown that Salmonella enterica bacteria survived for only fifteen minutes on copper (Zhu 2012). It is not always clear why copper is so effective, but evidence of its effects is abundant. "Copper exerts its toxicity to microorganisms through several parallel mechanisms, which can ultimately lead to the death of microorganisms even within minutes of their exposure to copper" (Gabbay 2009).
Copper is important for improving public health:
Its anti-pathogenic properties help prevent infections in homes, workplaces and hospitals. Copper pipes are widely used in plumbing because they can help preserve the purity of drinking water. Copper has antimicrobial effects that can inhibit microorganisms in water, such as bacteria, viruses, algae and infectious parasites in the drinking water supply. Copper and brass surfaces, such as door handles and tabletops, can also reduce the spread of disease-carrying organisms. Microbial food poisoning can be reduced by using copper surfaces for food preparation.
The Choice of Copper Alembics in the Distillation of Plant Material
Copper's properties lend themselves well to distillation; excellent heat transfer, efficient conductor, easily malleable, effective antimicrobial and a natural resistance to corrosion. In my opinion, it is the most suitable metal for hydrolates, although it may not always be the best for essential oils.
In the essential oils industry, stainless steel is the metal of choice for large stills. This is partly due to its lower cost, and also partly due to its non-reactive nature. When hydrolate and essential oils are distilled in stainless steel stills, they produce something called a 'still note'. The 'still note' is the result of sulphur and yeast compounds that have not been removed during the distillation process. This 'note' will eventually disappear over time, ranging from weeks to months, as the sulphur dissipates. When distillers talk about ageing or resting their essential oils or hydrolates, it means that they are waiting for the note to disappear before their products are marketable. This raises an important point; Hydrolates are perishable and have a much shorter shelf life than their essential oil counterparts. If it takes months for a Hydrolate distilled in a stainless steel still to lose this still offensive note, you will have reduced its shelf life by perhaps half or even more while you wait for the still note to diminish. A Hydrolate distilled in a copper still is immediately sweet and usable. This is a good reason to distill your Hydrolates with copper alembics! Copper is reactive, which is exactly why you want to use it to distil Hydrolates. Both sulphur and yeast occur naturally in plants. Sulphur smells and tastes foul. During the distillation process, copper binds to the sulphur ions and removes them from the distilled water.
It is because of this reaction to sulphides that it produces such sweet hydrosols directly from the still. Alcohol distillers have known for centuries that distilling spirits in copper stills yields a finer, cleaner product. There are some distillers who can modify their stainless steel stills by incorporating some copper somewhere in the condensation phase; but it was found that 'putting copper in a single section could not replicate the effect of full copper stills' (Harrison 2011). In other words, distillation with a solid copper still is preferable to distillation in a still with a combination of metals.
During my distillation workshops, one of the first experiments we do is a comparison between a distillate distilled on a copper still and one distilled on a stainless steel still. We keep all other variables constant. We use the same plant material, harvested at the same time, the same weight and ratios, the same temperature, the same water and the same distillation time. The students are part of the whole process and when we have finished the distillation there are always wrinkled noses when they smell the Hydrolate made on the stainless steel still, and expressions of surprise and delight when they smell the Hydrolate made on the copper still. The reason for these responses is reactivity.
WHY USE COPPER IN A ALEMBIC?
- in brief -
Copper absorbs sulphur-containing compounds and yeast cells that are produced during fermentation and whose presence is undesirable in spirits or essential oils. Sulphur compounds and yeast cells stink. Copper keeps the distillate sweet.
Copper reduces bacterial contamination.
Copper has excellent heat transfer properties, useful for both heating and cooling vapours.
Copper prevents the production of ethylcarbamate, a toxic substance formed from cyanides (cyanides are found in fruit stones and other vegetables).
Copper also improves the quality of the final product. If the quality is not microbiologically perfect, copper improves the aroma of the final product.