Incense sticks are used for various spiritual, meditational and therapeutic purposes. Their easy manufacturing process and affordable prices have stimulated market growth.
Nine small incense and joss stick factories were visited to assess the workers’ working conditions. Major hazards observed were high concentrations of dust and aerosol particles. Only few workers used personal protection equipment.
1. Mixing and Sifting
A variety of powdered aromatic woods and herbs are carefully measured and mixed, then sifted for consistency. It is important for the powder to be fine in order for it to knead, extrude and dry properly.
For combustible incense sticks, trails, cones or molds it is also recommended that the ingredients be ground to a finer consistency for even burning. This can be done using a mortar and pestle (absolutely required for gums and resins) or by hand-crank grinder or mill.
The incense mix is combined with a binder, traditionally a gum but lately more and more often a type of wood such as joss powder or tabu no ki (sometimes, incorrectly, called makko). Wood binders are very forgiving and are easier to work with than gum binders. They are not, however, as strong or long-lasting as gum binders. Amounts of a binder are added depending on the recipe and type of incense. The kneaded mixture is then either rolled onto bamboo sticks or, more commonly now, compressed into the shape of soft strands by hydraulic machine.
2. Kneading
Many types of aromatic herbs and resins are kneaded into loose incense mixes. These mixes can be used in combustible incense sticks and cones, or can be pressed into pellets to make non-combustible incense, called awaseke, nerikoh, or bakhoor.
Loose incense can be made by combining powdered wood and barks, with a variety of herbal and fragrant ingredients like dried flowers or finely chopped or ground spices. The mixture is then kneaded and mixed evenly. The mix is shaped into small pellets and placed on boards to dry.
Some hard gummy resins like galbanum and labdanum must be frozen or softened before they can be kneaded into the mix. Soft resins can also be poured or drizzled onto the loose incense mix and kneaded into it. Honey, balsams and liquid essential oils are also sometimes used to add flavor and aroma to the kneaded incense mix. This step can be done after the kneading is complete or during it.
3. Extruding
In this stage, the ingredients are pressed through a steel mould, which forms long strands of incense like spaghetti noodles. These are then dried slowly, allowing the soft strands to retain their fragrance.
Sandalwood, the classic incense ingredient, is still a favourite with many people around the world. However, production of this beautiful wood has been outpaced by demand and the supply is dwindling. Fortunately, there are other fine incense ingredients that can be used as an alternative.
Depending on the type of incense being made, a variety of different binding and perfume ingredients are added. These can be, as in the traditional case, a mixture of powdered aromatic woods and barks or, more commonly, a scented solvent.
4. Drying
Depending on the product line, some incense is aged. This is especially common with high-end mainichi-koh incense, which is made from precious woods like sandalwood that are increasingly endangered. The ageing process allows the fragrance to further blend and stabilize.
Once the kneaded incense is ready it is transferred from the model board (called Bon-ita) to cardboard drying boards that are stacked on top of each other. The stacks are then moved to a drying room that is carefully temperature controlled and humidity regulated.
Once the incense has dried, it is dipped in perfumes and allowed to dry again. Some incense may also be painted with a color to give it a more attractive appearance. The incense is now ready for sale.