Natural Binder in Traditional Chinese Incense

I saw a customer wrote on the reddit about a pack of incense she had bought online. The sticks were shedding powder in the box, and she wanted to know why. The answer is the binder, the material that turns loose powder into a stick. It also has a lot to do with how the stick smells when it burns.

The short answer. An incense stick is mostly ground powder, and powder does not hold a shape on its own. Old Chinese recipes used plant-based natural binder to do that job, like elm bark. You pound the inner bark with water and it forms a paste, because the bark carries a natural gum. Chinese herb books list the same bark as a medicine, so it appears in old formulas by name, with a dose written next to it. Most cheap sticks today use an industrial binder instead, and many of them get their scent from oil applied after the stick is made.

What holds an incense stick together?

Grind sandalwood and you get dust. Grind frankincense and you get dust. The binder does two jobs. It holds the powder in a shape, and it keeps the ember moving down the stick at a steady speed.

India's agarbatti industry publishes a standard masala recipe, and the proportions are worth knowing. About 40 percent is wood powder, the material that actually burns. Charcoal is around 20 percent. Ground bark binder is another 20 percent. Fragrance is the last 20 percent. So four fifths of the stick is there to hold the shape and carry the scent. Only the last fifth is the part you smell. That is why a bark binder has to burn almost odorless. If it had a smell of its own, it would sit on top of the sandalwood or agarwood and change the formula.

Why did old Chinese recipes use elm bark?

Bark was one option among several, and elm won on price and availability. It grows across northern China, and the inner bark was already in daily use. People ate it in bad harvest years, and they twisted the fiber into rope. It cost almost nothing. The same species, Ulmus pumila, grows along roads across the American plains, so the tree is not exotic here.

The old manuals treat elm bark as an ingredient with a weight in front of it. Volume 25 of the Ming manual Xiang Cheng (香乘) gives six mace of elm bark flour, about 22 grams, to one incense stick formula, weighed out beside costus and spikenard. The same formula tells the maker to grind everything into a very fine powder and work it with boiling water into extra thin sticks. A court formula in the same volume takes two mace. A molded tablet formula takes six tael, ten times the first dose, because a tablet has to hold a shape on its own.

A workshop that only wanted glue would not weigh it, and the weight changes with the product. Li Shizhen's Bencao Gangmu, written in the sixteenth century, calls the same bark the paste that holds a formula of aromatics together, forming incense into strips like thread. Writers on Chinese incense often cite that line as the first description of a stick shaped like a line. Elm is one of four barks in Asia used this way, and the names get mixed up in English.

The three laurel family barks are related to each other, and elm is not related to any of them. Makko comes from a laurel tree, so it behaves like elm bark in a paste even though the two trees are far apart. Several English guides call makko a kind of elm bark, which is where the confusion starts. What all four share is mucilage, a polysaccharide that swells in water and turns slippery, and that is the glue.

Is elm bark a medicine too?

The bark was never only a workshop material. It has its own entry in the Chinese materia medica, and the entry is a long one. The Shennong Bencao Jing, the oldest surviving Chinese herb book, lists elm bark among the upper grade materials. It gives the bark a sweet, neutral nature and says it opens the water passages and moves the bowels. Later books add channel assignments. Li Shizhen puts it in the hand taiyang and hand yangming channels, and the Bencao Qiuzhen puts it in the stomach and the large and small intestines.

Modern references describe its chemistry as gum, tannins, sterols and fatty oil. The gum is what makes the powder stick, and it is why the same bark shows up in both the herb books and the workshop.

Why do cheap sticks skip the bark?

Elm bark was cheap and it worked, so the switch came down to money and speed. The replacement is sodium carboxymethyl cellulose, usually written CMC, an industrial powder made from treated cellulose. Suppliers sell an incense grade and advertise it as a direct replacement for elm bark flour. It dissolves in seconds, and it skips the mortar work that bark requires.

The process changed with the binder. In the dipped method, a factory makes a plain unscented blank and soaks it in fragrance oil. That oil is thinned first, usually with mineral oil or a solvent called diethyl phthalate, at about one part oil to three parts thinner. The scent sits on the surface. In a pressed stick, the scent is mixed into the paste and runs all the way through. The fragrance in that oil is a separate subject, and I covered it in my post on natural and synthetic incense. Both kinds look the same in the box, so the difference only shows up when you burn one.

How can I tell which one I have?

Four checks will tell you which kind you are holding, and you can run all of them at home.

• Smell it cold. A pressed stick smells like the woods and resins it was made from before you light it. A dipped stick often smells sharp when cold, and the scent sits on top of something plainer.
• Break one open. A bamboo splint down the middle means the stick was coated, not pressed. That alone proves little, because good Indian masala incense is rolled onto bamboo by hand. Look at what is on the splint. A dipped blank carries a thin, even layer that peels off in flakes, with pale powder underneath. A masala stick carries a thick, uneven coat that crumbles between your fingers, and a pressed stick is powder all the way through with no splint at all.
• Read the ingredient list or ask the seller. Look for the words binder, gum, jigat, joss powder, makko, CMC or carboxymethyl cellulose. Jigat and joss powder are ground Litsea bark, makko is ground Machilus bark, and CMC is the industrial option.
• Watch the burn. A dipped stick tends to burn fast and hot with a hard edge at the tip. A pressed stick burns slower, and the ash falls soft. If a stick keeps going out, the cause is usually airflow, which is the subject of how to burn incense.

What Panda Incense does

Our sticks are pressed from powder and have no core, so the first check is easy. Break one open and the cross section is powder all the way through. The binder is bark powder of the nanmu powder, worked in with water. There is no CMC in the paste, and nothing is dipped afterward. What you smell on a cold stick is the wood and resin that went into it.

That is where the cost comes from. Bark binder takes time to work in, and the sticks dry for several days before packing. A dipped stick needs far less of that time.

A first stick can smell like a medicine cabinet if you are used to fragrance oil. That is the material doing the work, and I wrote about why it reads that way in  why Chinese incense smells medicinal. Burning incense is a sensory practice.