The Whole Plant Extraction Blog

Which Method of Ethanol Extraction is Right For You?

Fritz Chess

Botanical Distillation has seen a groundswell of popularity in recent years. But which method is right for you? 

The Eden Labs’ commercial distiller offers five methods of extraction and more than eight ways of distilling. New innovations have made it possible to easily transition from one method to another with the same batch of herb allowing the operator to collect different distinct fractions of extract. This ability to "fractionate" and separate the light oils from the heavier oils and resins is one of the features that makes Eden Labs’ distillers/extractors truly unique.

Coldfinger Extraction

coldfinger commercial unit.jpgRight: Coldfinger Commercial Unit

Best for: Alcohol tinctures, herbal medicine

Coldfinger extraction is the method on which Eden Labs was founded. Coldfinger allows the user to do a very thorough extraction using a small amount of solvent which yields a thick, concentrated extract. If the desired end product is an alcohol-based tincture, which is very common in herbal medicine, flavorings, and perfumes, this is the best method.

How it works:

A perforated basket is filled with ground herb and suspended above a pool of solvent.  A condenser is positioned above the basket and cooled.  The condenser is designed so that solvent vapor will condense and drip in an even rainfall pattern over the basket of herb so it will extract evenly and thoroughly.

Right: Coldfinger Professional Unit, capable of Steam Distillation.

Gentle heat is applied to the solvent causing it to vaporize. The vapor liquefies on the condenser and drips from the drip points. A continuous cycle of solvent vaporizing from the bottom of the vessel, liquefying and dripping across the basket slowly leaches the soluble constituents from the herb. The extract laden solvent flows out of the perforations at the bottom of the herb basket and into the bottom of the extractor.

The extract has a much higher boiling point than the solvent so it stays in the bottom of the extractor while the same solvent continuously vaporizes, liquefies, and flows through the herb bringing extracted constituents with it, and then liquefies again.

While gentle heat is the primary means for getting the solvent to vaporize and distill through the herb, vacuum can also be used to enhance the process. Vacuum lowers the boiling point of the solvent so less heat can be used and/or the distillation/extraction can be done faster. Deep vacuum allows the Coldfinger process to be accomplished as low as 105F. Even without vacuum the inverted Coldfinger condenser hanging down into the boiling flask allows for lower temperature distilling well below the boiling point of the solvent.

Steam Distilling

steam distillation unit.jpg

Right: Steam Distillation Unit for Extraction

Best for: Light, volatile oils (essential oils)

How it works:

Steam distilling is a method of extraction which collects only the light, volatile oils known as essential oils which are generally monoterpenes. This technique involves either placing fresh herb in a vessel of boiling water or suspending the herb above the boiling water in a perforated basket so that steam passes through the herb. In either case, the steam strips the light oils from the plant material and carries it to a chilled condenser where the oil-entrained steam liquefies.

The condensed fluid separates into two layers: the lower layer is called hydrosol. It is a milky looking liquid composed of water soluble oil and water. Floating on top of the hydrosol will be a thin layer of essential oil.

There are two design innovations that makes Eden Labs' steam distilling unique:

  1. The entire extractor has been designed so that after steam distilling, the system can be reconfigured to move straight into Coldfinger solvent extraction or stirred reactor extraction to get the heavier compounds out of the herb.
  2. A Coldfinger style condensing system with the option of using vacuum allows the process to be done at a temperature below boiling water (212°F).

Stirred Reactor

vacuum distillation.jpeg
Right: The Eden Labs' Vaccuum Distillation Unit is capable of stirred reactor distilling, along with 4 others methods.

Best for: Fast extraction, materials requiring agitation, heavier compounds

Stirred Reactor is the most common method of extracting herbs and other solids. The material is ground up and placed in a vessel of heated solvent and stirred to get maximum exposure and mixing between the material and the solvent.

How it works:

The Eden Labs method uses the same basket that is used for Coldfinger and steam distilling. To start, the tank is filled about 3/4 full and the tank jacket is set at the desired temperature. Cold and hot extractions are possible.  

Cold is used when only certain compounds are desired and other constituents are preferred to be kept in the plant material. Heat is used when the operator wants to extract everything possible.

When the tank is 3/4 full, the stir motor is turned on and ground plant material is slowly poured into the vessel. Once this is finished the tank is topped off with solvent and closed up.

Stirring is done usually for 90 minutes and the finished extract is pumped out to a storage tank. It is possible to leave the pump running after all the liquid is drained out. This will pull a mild vacuum which helps to press excess liquid out of the herb thereby helping to get the last of the extract and allowing the basket of spent herb to be lifted out of the tank without dripping solvent and off gassing excessive solvent vapors into the workplace.

Summary

The three different extraction methods above are actually five different methods because Coldfinger and steam distilling can be done at atmospheric pressure or under vacuum. Working under vacuum is more complicated and yields substantially different results. We’ll cover vacuum distillation in a future blog post.

So what should I use?

Coldfinger is the best method for thoroughly exhausting plant material of everything that is in it. Steam distilling is best for getting only light, volatile essential oils. Stirred reactor is a fast, easy method for getting 70-80% of the constituents out of a botanical.

March 01, 2017