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How To Distill Essential Oils

How To Distill Essential Oils

It may look intimidating, but extracting essential oils from plants is not as hard as you think! 

With the necessary glassware, a few clamps and stands, plastic buckets, and this guide, you'll be ready to give it a try.

About Essential Oils:

First, a little about essential oils. As I’m sure you’re aware, many of the pleasing characteristics of the plants around us come from natural chemicals within the plant.

Some of these chemicals are water soluble, and others are not. When we use the phrase essential oils, we’re referring to the natural plant chemicals which are not water-soluble.

Many plants, especially plants that are food safe, have essential oils that have pleasing aromas, invigorating tastes, or holistic uses. One great example is spearmint, widely available and found in nearly every grocery store.

A brief online search reveals purported uses of spearmint essential oil may include relieving indigestion, nausea, vomiting, and gas. It also smells... well, very minty. 


What You'll Need

To obtain the essential oils of spearmint, we’ve got a bit of a job because they only comprise about 1-2% of the biomass of the plant. Additionally, they are vaporizable, which means if you boil the plant in an open container, almost all of the essential oils leave with the water vapor.

You could try a closed container such as a pressure cooker, but I don’t even want to think about the mess this would make, nor how you’d separate the oils cleanly from the cooled spearmint mush.

The simplest and cleanest way is to use a distillation apparatus. A beginner distillation kit such as this Eisco Essential Oil Distillation Kit can be found online. A quick search reveals many varieties, but this complete kit contains all the glassware you need to get started quickly and easily.

The distillation set includes the following components:

  • (2) 125ml Pear Shaped Separating Funnels - PFTE stopcock and stem with cone
  • (1) 500ml Boiling Flasks – round bottom
  • (1) 500ml Boiling Flask – flat bottom
  • (1) 500ml Biomass Flask 
  • (1) Multiple Adapter - two parallel necks
  • (1) Vertical Recovery Bend Adapter - with thermometer socket
  • (1) Receiver Adapter
  • (1) Jointed Liebig Condenser
  • (10) Size 24 Joint Clips - green
  • (2) Polypropylene 24/40 Interchangeable Stoppers
  • (1) Soft, Rubber Tubing
  • (1) Cork Flask Stand

If you’re like me, you don’t have a chemistry workbench with all the amenities of a scientific laboratory. The distillation process requires a heat source and a condensing water source.

A stove works fine for the heat-source. The water source took a little more tinkering, but the solution for me ended up being a siphon system using two 5-gallon buckets.

It was simple and inexpensive – more on this below. You will also need some way to support the apparatus. I used a handful of stands and clamps I had lying around. But you can also find base, rod, and clamps available online. I used equipment most similar to

1 x STDRDAB03

2 x MTST5

3 x PRCMP06BH

Getting Started:

Once you’ve collected all the components, the first task is to fill the biomass flask (see the image above; it’s the round flask with a top and bottom opening) with spearmint.

Once the experiment is running and steam permeates the biomass flask, the contents will break-down and naturally compress. Thus, you should feel comfortable filling the biomass flask so that it is quite full (without placing undo pressure on the flask).

Chopping the plant matter can help with this process, but it is wise to put a layer of unchopped leaves in first. That way plant matter is less likely to migrate in large chunks to the steam source flask (the round flask with only a top opening). This will make cleanup simpler and prevent frothing of the boiling water.

I was able to fill the biomass flask with three small bunches of spearmint leaves purchased at the local grocery store.

The second task is to assemble the apparatus as shown in the figure below. Here are some other tips:

  • The glass is fragile, so take care that stresses are minimized across the apparatus.
  • Assemble and support the apparatus incrementally from left to right to reduces stresses across the apparatus.
  • Do not attach a joint clip between the receiver adapter and the separating funnel. This is because there needs to be a gap to allow excess pressure to escape. You should also place the stoppers only very loosely – just in case.
  • The nozzles on the Liebig condenser should be pointed up – this reduces air bubbles.
  • Don’t cut the rubber tubing until you’ve figured out your water supply system.
  • Slight variations in the glass blowing process may mean that adapter angles cause a difference in the bottom levels of the two boiling flasks. If your heat source is a stove-top, you may need to be creative and bring a table alongside it if the collection flask is below the level of the flat-bottom flask.
  • Be sure that the bottom of the flat-bottom flask is flush with the heat source if a flat conduction heat source is used such as a hotplate or electric stove. Gas-based heat sources don’t carry this concern.
  • If you are using a heating mantle, use the round-bottom flask for the steam source and the flat-bottom flask for the collection flask.

Finally, once the apparatus has been set up you need to figure out the water system. I used a siphon system made from 2 clean 5-gallon buckets. As long as the drain bucket is well below the source bucket, the siphon will flow uphill through the apparatus and down the to drain bucket. When the drain bucket gets full, you simply dump it back into the source bucket.

For me, it was simplest to dump the drain water in the sink and refill the source bucket with a pitcher. To do this, I simply pinched the drain tube with a clothespin to stop the flow of water while I emptied the bucked. The flow rate can be controlled by adjusting the relative height of the buckets or using a clothespin to slightly constrict the tubing.

Starting the siphon was a little tricky. The most common method for starting a siphon is to suck water from the source bucket through the tube, but it always left a big air-bubble in the Liebig condenser.

The best method I found was to partially fill the drain bucket and suck the water backwards, up through the apparatus and then pinch the source tube tightly and quickly transfer it to the source bucket. Then gravity takes over and reverses the flow through the apparatus. This method had much smaller air-bubbles.


Let the Distillation Begin:

1.     With the apparatus built and the water supply set, you need to add water to the boiling flask via the separating funnel above it. You should only fill it up halfway to allow room during boiling. Close the stopcock on the separating funnel. 

2.     Start the heat source and bring the steam source flask to a strong boil. Be sure the stopcocks are closed on both separating funnels. 

3.     Steam will pass up through the plant matter vaporizing the plant oils and water-soluble organic matter, which will then condense in the condenser tube, and flow into the separating funnel. At this point, it’s fun to watch the biomass slowly breakdown and the vapor condense and drip into the separating funnel. It’s also fun to observe the development of the strong mint aromas as the process evolves. 

4.     You’ll need to be sure to keep the source bucket of the condensing water if you are using a siphon system. 

5.     Also, the contents of the separating funnel should be partially but not completely emptied into the collection flask periodically by turning the stopcock at the bottom of the funnel and closing it again before the liquid is completely drained.

The plant oils rise to the top of the condensed liquid in the separation funnel. By not emptying the condensed liquid completely, the oils are retained and will accumulate over many emptying cycles.

The non-oil liquids, called hydrosol, can be discarded. The hydrosol will be cloudy in the beginning of the distillation process, but overtime will become clearer as the extraction process plateaus. Very clear hydrosol is an indication that most of the oils have been extracted from the plant matter.        

You may notice that the color of the water in the boiling flask will take on a light green hue, then yellow color, and finally a strong brown color. This is from broken-down biomass that drips back down into the boiling flask.

Any of the essential oil that may make its way to the boiling flask, will evaporate and find its way back up through the biomass and into the condenser. 

6.     When you are satisfied that as much of the oil has been extracted as possible, you can empty the remaining hydrosol in the separating flask one last time, closing the stopcock just before the oil layer reaches it. Then the oil can be emptied into a small collection vial. 

Clean Up:

Carefully disassemble the apparatus and wash each piece in warm soapy and then rinse. Lay out a towel and let the pieces air dry. You can easily remove the biomass using the blunt end of a single chopstick to push it through the wide neck opening on top.

What’s Next:

You can use this same methodology to extract and distill a variety of essential oils! Other commonly available plants associated with popular essential oils include lemons, rosemary, oranges, marjoram, grapefruit, and cloves. Best of luck with your distillation adventures!

Next article The Many Densities of Water