Bento boxes: carrying a meal

A bento box holds food in a portable container. Its body carries the meal, the lid covers it, and partitions or removable inner boxes separate foods. A box can have one tier or several stacked tiers. Compartments and tiers solve different organisational tasks.

Wooden boxes, bentwood vessels and woven containers have all carried meals. Bentwood forms the walls from curved strips; woven boxes interlace bamboo or willow. Lacquered wood adds a surface coating. Seams, interlacing and coating are visible clues to their different construction.

A lecture by conservator Hiroshi Kato, recorded by the ICU museum, traces a change from bentwood meal vessels such as mosso and menpa to elaborately decorated forms from the Momoyama period onward. Tokyo National Museum’s seventeenth-century lunch box with a stone-hauling design is a surviving named example. The history of carrying meals therefore extends beyond the history of these decorated boxes.

Odate bentwood ware uses straight-grained cedar boards for its curved walls. Maker Kurikyu describes softening a board in hot water, bending it into a cylinder, gluing the overlapping ends, securing them with strips of cherry bark, and fitting a separate base. The bark stitching is part of the joint, while the bottom closes the ring of wood.

In MIHO’s Unkin Maki-e set, four food tiers stand beside a bottle within the carrying frame. A rectangular tray sits above them and a handle tops the frame. Food and drink occupy separate vessels that travel together. Views from opposite sides reveal maple leaves and cherry blossoms; the decoration continues onto the bottle and handle, connecting the separate pieces.

An anodised coating contains microscopic pores through which water or chemicals can enter. RIKEN researcher Miyata found that high-pressure steam closed the pores and improved corrosion resistance; the steam-sealing method was patented in 1929. Pilot production, patent licences to other firms and a specialist processing company established in 1934 helped take the treatment from research into manufacturing.

Postwar changes also concerned shape and printed decoration. Plenus’s historical lunch-box exhibition includes 1950s anodised boxes with character designs and 1970s book-shaped boxes intended to fit beside textbooks. The latter used a flattened rectangular body with separate spaces for rice and side dishes.

Some lids use clips, and some add a gasket to close the joint between lid and rim. A band or wrapping cloth can also hold a lid in place. Restraining the lid does not itself create a liquid-tight joint, so a container for soup may use a different closure from an ordinary box for drier foods.

An insulated box slows heat loss; a self-heating container adds a source of heat. One type of pull-string bento container uses the heat released when water reacts with quicklime, or calcium oxide, to warm the meal. It combines a heating system with the food container, rather than relying only on insulation to retain existing warmth.

Kobayashi uses Nalhot containers for products including its grilled beef-tongue bento. The supplier’s section diagram places the food tray above a heating unit containing quicklime and a water bag, with an insulating pad underneath. Pulling the string initiates the reaction; heat reaches the food through the tray and steam inside the box. The reactants occupy their own compartment. This particular container must not be microwaved.

Contemporary containers use plastics, metals, wood and paper, in both disposable and reusable forms. Moulded plastic, metal construction and wooden walls offer different structures. Insulation, partitions, closures and removable parts can appear in different combinations. Material, lid and internal organisation together shape how a box is used.