Key Differences at a Glance
| Feature | Steam Distillation | Hydro-distillation |
| Material Contact | Resin is separate; steam passes through it. | Resin is submerged in boiling water. |
| Heat Source | Steam is injected from an external boiler. | Water is heated directly from below. |
| Primary Use | Common industrial standard. Efficient, high-yield, controllable. | Traditional/Artisan method. Favored for resins and delicate flowers. |
| Potential Result | A "clean," bright aromatic profile. | A "fuller," deeper, more complex aromatic profile. |
1. Hydro-distillation (The Traditional Method)
This is a much older, simpler, and often gentler method, still widely used for dense materials like resins, woods, and delicate flowers.
How it works:
The frankincense resin is placed directly into the still and is completely submerged in water.
The still is heated from below, bringing the entire mixture of water and resin to a boil.
The steam that rises from the boiling water passes through the resin, collecting the volatile oil compounds as it goes.
This steam-and-oil mixture is then condensed and collected in the same way as steam distillation.
Key takeaway: The resin is boiled in the water. Many artisan distillers prefer this for frankincense, believing it "coaxes" the oil out more slowly and can extract some heavier aromatic molecules that high-pressure steam might miss, resulting in a "fuller" or "deeper" aroma.
The most common, large-scale industrial method is steam distillation. However, hydro-distillation is a more traditional method that is still favored by many artisan distillers, especially for resins.
Here is a detailed explanation of both processes.
2. Steam Distillation (The Common Method)
This is the modern industry standard for its efficiency and control.
How it works:
The frankincense resin (often ground into a powder to increase surface area) is placed on a grate or perforated grid inside the still.
The resin does not sit in the water.
A separate boiler generates high-pressure steam, which is then injected into the bottom of the still.
This hot steam (over 100°C) is forced through the frankincense powder, rupturing the oil-bearing sacs in the resin.
The volatile essential oil compounds are carried away with the steam.
The steam-and-oil mixture is passed through a condenser, which cools it back into a liquid.
This liquid (the essential oil and water, now called a hydrosol) is collected. The essential oil naturally separates and floats on top of the water, where it can be siphoned off.
Key takeaway: The resin is hit by "dry" steam, not soaked in "wet" water. This is generally faster and more efficient for large volumes.