How oud oil is made: from wood to bottle

Most fragrance materials are extracted and used quickly. Oud oil is unusual twice over: its production takes far longer than most, and the oil itself is widely regarded as continuing to change for years after it leaves the still. This guide follows the process from resinous wood to finished bottle. The technical comparison of methods is in oud oil distillation methods.

It starts with resin

Everything depends on the resin an Aquilaria or Gyrinops tree produces in response to wounding and infection, as described in how agarwood resin forms. Plain, unresinated wood, often called whitewood, carries little scent and is not worth distilling. The resin content of the starting wood sets the ceiling for both how much oil a batch can give and what it will smell like.

Sorting and grinding the wood

Harvested agarwood is cleaned and sorted. The best, most resinous pieces are usually worth more sold whole as chips or carvings, so oil is commonly distilled from lower-grade wood, offcuts and smaller pieces, although some distillers deliberately use high-grade wood for prized oils. For distillation the wood is chipped or ground into small pieces or powder, which exposes more surface to water and heat.

Soaking

Before distilling, the ground wood is soaked in water, often for one to two weeks and sometimes longer, occasionally with deliberate fermentation. Soaking softens the wood and helps release the oil, and its length matters: in a 2020 laboratory study, wood soaked for 14 days gave about twice as much oil as wood soaked for 6. Distillers also adjust soaking to shape the scent of the finished oil.

Distilling

The soaked wood goes into a still. In traditional hydro-distillation it is boiled in water, and the rising steam carries the volatile aromatic compounds into a condenser, where it cools back into liquid. This is slow: one comparison of extraction methods reported hydro-distillation taking around seven days, against about four hours for supercritical CO2 extraction. Steam distillation and CO2 extraction are the main alternatives, each giving a somewhat different oil.

Separating oil from water

Oil and water do not mix, so the condensed liquid separates on its own. The oil usually gathers at the surface and is drawn off carefully, often over the course of the run. The water left behind, the hydrosol, keeps a faint scent of its own. Some distillers return it to the still and some sell it. Any water left in the oil can affect its stability, which is why careful separation matters.

After the still: ageing

Freshly distilled oud is rarely treated as finished. Distillers and collectors widely describe young oil as sharp or pungent, sometimes with a strong "barnyard" edge, and say the same oil becomes smoother and rounder after resting. Colour is often reported to deepen over time. These changes are generally put down to slow chemical reactions such as oxidation, though the specifics are not well studied, and older is not automatically better: starting quality and storage matter as much. Storing oil well is covered in how to store agarwood.

Why so little oil comes out

Yields are very low. Published laboratory figures range from roughly 0.01 to 0.14 percent of the wood's weight, about 0.1 to 1.4 grams of oil per kilogram of wood. On those figures, a single 12 ml tola can take anywhere from around 8 to over 100 kilograms of wood. Low yield, long soaking and slow distillation are the main reasons genuine oud oil is expensive, as covered in why oud oil prices vary.