Kusudama is a traditional Japanese art form that has evolved into what is now generally referred to as modular origami. To the untrained eye, the difference may seem negligible. With some remarkable examples, here is the basic difference between the two.
The form of Kusudama goes back to before written history. The general consensus is that they were used to hold bunches of herbs or flowers as urban culture took hold. With urbanization the desire for objects with both utility and beauty took greater hold. Before this the plants would have been hung on their own and the kusudama evolved as an aesthetically pleasing receptacle for both potpourri and incense.
Incense
Incense is composed of aromatic biotic materials. It releases fragrant smoke when burned.
A potpourri is a selection of dried plants which give off light fragrances throughout the domicile. Although popular in Japan for countless centuries, it wasn't until the dawning of the Age of Aquarius that they became popular in western culture. Potpourri acquired a slightly hippy label, which in the west it has never been quite able to shrug off. As anyone who has experience of potpourri will testify, unless contained within some hopefully attractive container, the dried plants of which it is made up can get everywhere. The kusudama solves this problem with both utility and decor.
A Potpourri
A dried rose. Dried flowers are a common component of potpourris
It is more likely that traditional kusudama had a more important function than just simply making the house smell nice. Its literal translation is ‘medicine ball' from the words kusuri (medicine) and tama (from you guess it, and with a little mutation, the word for ‘ball'). Traditional designs, such as the one above, are sometimes indicative of what lies within. As Rolf Harris would say, can you see what it is yet?
The kusudami is usually made by the gluing or sewing together of a large amount of small pyramid-shaped folded paper. They are attached via their points and eventually, with great care, can be formed in to a sphere. Generally the spheres are displayed on their own but a final flourish - a tassel - is sometimes used to dangle from the bottom. These are no ordinary tassels - the Japanese can rarely be accused of doing things by halves.
The words glue and sew are pivotal in understanding the difference between kusudami and modular origami. In kusudami this is entirely permissible but in modular origami this is frowned upon - the folded piece of paper must be held together by nothing more than the neighboring piece - and an awful lot of tension.
Modular origami is a direct descendent of kusudama and the pivotal difference has already been explained. The jury is still out about whether kusudama belongs in the origami family of paper folding with many saying it does while others say that because of the inclusion of sticking or sewing it doesn't count. The form, however, remains wonderful in its own right.
As techniques developed, modular origami - the more challenging of the two forms - became increasingly popular. Origami rules insist that the final product must be achievable from a single piece of paper. However, one piece of paper cannot ever produce more complex designs and modular (sometimes known as ‘unit') origami came about as people wanted to experiment with larger shapes. The process of creation is fascinating.
Preparation is crucial. Multiple sheets of paper are necessary for one single piece of modular origami and this is not done on an ad-hoc basis. Many sheets are folded in to their individual module before the process of creating the final product begins. The colors and patterns are also decided at the creative design stage.
The act of folding creates pockets in the small modules. It is in to these pockets that flaps, a product of the process of folding, will be introduced in order to create the larger construct. The process of creating the units is painstaking and time consuming enough. When it is time to construct the design it is there where the real patience and tenacity of the origamist must show through.
Modular origami is first recorded in the early eighteenth century. The cut and paste technique is not allowed of course, but what separates modular origami from other types where more than one piece of paper is allowed is that identical copies of a single fold design may be linked together to get to the finished product. 
Additionally, more than one type of module is also allowed. These are usually ‘undercover' units, which are used to hold the whole thing together. If they were used in plain sight then it would not be considered true modular origami.
Modular origami found a new audience in the nineteen sixties, both in Japan and notably in the US. Experimentation with the form continues. The Menger Sponge, above, makes for quite a challenge - and hopefully it won't start emitting 'resistance is futile' noises in the future. Many hundreds of new designs have been explored to further evolve this sublime combination of art and design.
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