Aromatic Materials & Fragrant Woods

Agarwood

Agarwood is not a wood in the ordinary sense. Certain tropical trees, principally of the genus Aquilaria, respond to fungal infection or physical injury by depositing resin in the affected heartwood. The resin-saturated wood is agarwood. A healthy tree contains none, and there is no external sign of what is inside.

The scent, released by heat, is complex and difficult to describe: variously woody, sweet, resinous, animalic, with notes people compare to honey, leather, spice and cool camphor. It changes as the material heats, which is precisely why appreciation focuses on it.

Grading has traditionally been by density and resin content. The highest classical grade sinks in water because the resin has displaced enough of the wood's structure; lesser grades float or half-float. A separate and higher category, known in Chinese as qinan and in Japanese as kyara, describes material that is softer, oilier, and produces a distinctly sweeter and more penetrating scent. Qinan is extraordinarily expensive and its formation is not fully understood.

Origin matters. Material from Hainan is historically the most prized in China and is now essentially exhausted in the wild. Vietnamese material, particularly from the Nha Trang region, is highly regarded. Cambodian, Indonesian, Malaysian and Papuan material each have recognised characteristics, generally described as progressively heavier and less refined as one moves south and east, though this ranking reflects Chinese taste rather than any objective scale.

Sandalwood

Sandalwood is a true fragrant heartwood from a partially parasitic tree. The classic source is Mysore in southern India, and old-growth Mysore sandalwood is the standard against which others are measured: creamy, sweet, persistent and even.

Indian sandalwood was severely overexploited, and the trade is now tightly controlled with most legal supply coming from plantations, including large ones in Australia. Indonesian sandalwood from Timor is a different regional type. Various unrelated woods are sold as sandalwood and are not.

Sandalwood is used in far larger quantities than agarwood, both as a base for compounded incense and burned alone. It is also carved, and the shavings and offcuts from carving have historically supplied the incense trade.

Resins

Frankincense and myrrh, both from trees of the Arabian peninsula and the Horn of Africa, entered China through the maritime trade and appear in both incense recipes and medicine. Frankincense is bright, lemony and slightly peppery when burned; myrrh is darker, bitter and medicinal.

Benzoin, from Southeast Asia, is sweet and balsamic and is used as a fixative in compounds. Storax and dragon's blood also appear in recipes. These resins are cheaper than the fine woods and do most of the work in compounded incense.

Animal materials

Musk, from the gland of the male musk deer, is the most important animal ingredient in classical recipes. It is powerfully persistent and functions as a fixative, holding other scents together. Musk deer are now protected and international trade is prohibited; almost all musk in commercial products today is synthetic, and this is a good thing.

Ambergris, a substance formed in the digestive system of sperm whales and found washed ashore, is used similarly. Its legal status varies by country. Civet, from a gland of the civet cat, appears in older recipes and raises obvious welfare problems.

These ingredients belong to the historical record and it is worth knowing what the classical recipes specified. It does not follow that they should be sought out now, and there are good synthetic substitutes for all of them.

Camphor, borneol and plant aromatics

Camphor and borneol are crystalline, cooling and penetrating, and are used in small quantities to give lift to a compound. Borneol in particular has a long history in Chinese use and appears in both incense and medicine.

A long list of Chinese aromatic plants is used in compounding: angelica root, spikenard, patchouli, clove, cassia bark, star anise, various citrus peels, and many more. Most are also medicinal materials, and the recipe literature moves between the two purposes without any sense of crossing a boundary.

Compounding

Most traditional incense is a compound rather than a single material. A recipe specifies proportions of aromatics, a binder, and sometimes honey or fruit as a humectant and sweetener. The mixture is ground, blended, kneaded and then aged, often buried in a sealed container for weeks or months, which allows the components to marry.

The binder deserves mention because it is the least glamorous and most consequential element. Powdered bark from certain trees, notably a machilus species, provides adhesion and a controlled burn rate without contributing much scent. Poor binder, or too much of it, is the commonest fault in cheap incense and produces a smoky, papery smell that overwhelms everything else.

Recipes were named, collected and transmitted, and the surviving Song and Ming manuals contain hundreds. Many are impractical today because they specify musk, or materials no longer identifiable, but the structure of the recipes is informative and modern makers work from them.

Judging material

Several tests are traditional and several are unreliable. Sinking in water indicates high resin content and is the origin of the Chinese name for agarwood, but it can be faked by soaking wood in resin or oil, by injecting, or by adding weight.

Visual inspection of the resin pattern, colour and grain tells an experienced eye a great deal. Scraping a small amount and warming it is the only real test, since the scent under gentle heat is what is actually being bought.

Common adulterations include ordinary wood soaked in agarwood oil, wood impregnated with synthetic fragrance, material artificially inoculated and harvested too early, resin-poor wood dyed dark, and pieces built up from fragments and adhesive. Synthetic qinan is a known product. The market is sophisticated and a beginner will not reliably detect any of this.

How the classical sources organised materials

The Song and Ming manuals classify aromatics in ways that repay attention because they reveal what mattered to the compilers. Materials are grouped by origin, by form — wood, resin, root, flower, animal — and by function within a recipe, which is the most useful grouping.

Functionally, a compound has a principal aromatic that supplies the character, supporting materials that fill out and round the scent, a fixative that slows evaporation and holds the whole together, and a small quantity of something sharp and cooling to give the mixture lift. This is essentially the same structure as a perfumer's accord, arrived at independently, and it explains why musk and borneol appear in so many recipes despite contributing little scent of their own.

The manuals also grade by the intended occasion. There are recipes for scenting clothing, for a study, for a bedroom, for ritual use, for summer and for winter. The assumption throughout is that different situations want different scents, which is a more practical outlook than the modern tendency to seek a single best material.

Buying sensibly

Given the above, the practical advice is unromantic. Buy from a seller who will let you smell material before purchase, who states origin and whether the material is wild or cultivated, and who is willing to say when something is ordinary.

Start with sandalwood and with compounded incense rather than with agarwood, since these are affordable, less faked and perfectly capable of teaching your nose. Buy tiny quantities of agarwood when you do; a gram is enough for many sessions of gentle heating.

Treat any wild agarwood offered at a low price as certainly not what it claims to be. And be aware that plantation material, honestly sold, is the responsible option and can be very good, particularly from established Vietnamese and Malaysian producers.

Conservation and law

All Aquilaria species are listed under the international convention controlling trade in endangered species, which means cross-border movement requires permits. Several species are assessed as threatened or critically endangered. Because the resin cannot be extracted without cutting the tree, and because there is no way to tell from outside whether a tree contains any, harvesting is destructive and indiscriminate.

Sandalwood in India is similarly regulated, with the state controlling harvesting. Musk deer are protected and trade is prohibited.

These are not remote concerns. The revival of interest in incense over the past thirty years has been a significant driver of demand, and a purchaser is part of that system. Buying cultivated material, buying small amounts, and using the smokeless heating method that requires very little material are all reasonable responses.

Key points

• Agarwood is resin deposited by an injured tree, invisible from outside, which is why harvesting is destructive and indiscriminate.
• Grading is by resin content, with the traditional highest grade sinking in water, and the separate qinan category being softer, oilier and far more expensive.
• Sandalwood is used in much larger quantities than agarwood and is now largely plantation-grown under control.
• Musk, ambergris and civet appear in classical recipes but are protected or ethically problematic, and good synthetic substitutes exist.
• The binder is the least glamorous and most consequential element of compounded incense, and poor binder is the commonest fault in cheap sticks.
• Adulteration is sophisticated and the only real test is warming a small amount, so buy from sellers who let you smell before purchase.