Skip to 0 minutes and 3 secondsNext let us look at detchōsō ("pasted-leaf") binding. The leaves are joined together with glue, as with scrolls, but the area where the glue is applied is different. Each leaf is first folded in two and pasted to the next leaf near the crease. When you look at it from the side the shape of each leaf resembles a "y". The area where the glue is applied is called norishiro. The inner side of each folded leaf opens completely, but the outer side which is connected to the next leaf only opens up to the glued part. Then again there is a leaf that opens up completely followed by one ―the glue has come off here―that only opens partially.
Skip to 0 minutes and 55 secondsThis alternating of fully opening and partially opening two-page spreads is the distinctive characteristic of the detchōsō binding. In terms of structure and how you turn the pages, it is very similar to modern books and in fact it is considered the oldest type of book-style binding. However, one shortcoming is that, as you have just seen, the glue tends to come off easily causing the pages to fall apart. Another major defect is that―please look at this―this is a very old example of detchōsō binding, as you can see, there are many small holes. They are especially numerous in this area here. What these are is wormholes made by insects that feed on paper.
Skip to 1 minute and 54 secondsInsects that feed of paper are called shimi in Japanese, but here the culprit is not shimi. A family of insects called shibamushi or shibanmushi (Anobiidae) which have a hard shell and resemble the rhinoceros beetle lay their eggs on the paper and the small larvae then feed on the paper to grow. They don't dislike paper but their favorite target is the glued area, which is the most nutritious. Therefore, this is the most easily damaged part. And of course, when this part is damaged, the entire book falls apart like this. So this type of binding presents a number of major flaws. Which is why starting from around the 13th century, it gradually fell into disuse.
Skip to 3 minutes and 1 secondHaving said that, the famous monk Kūkai used the detchōsō format for the Sanjujō sasshi (the Thirty Books), the set of latest Buddhist scriptures that he brought back from China and which are now designated a National Treasure. In books brought to Japan from China ―this has to do with the type of paper― there is writing only on the inner side of each folded leaf and the pasted side is left blank. Detchōsō books made in Japan, however, usually have writing on both sides of the leaf. Because of Kūkai's legacy, the detchōsō format continued to be used within the Shingon sect of Buddhism up until the modern period, so long after everybody else had stopped using it.
Skip to 4 minutes and 9 secondsAnd here I conclude my explanation of pasted-leaf binding.
Main Binding Methods 3 - Detchōsō
Read the article then watch Prof. Sasaki introduce the detchōsō binding method.
III. Detchōsō (oriental style binding)
The third main binding style is the detchōsō (oriental style binding). Sheets of paper are folded in the middle, placed on top of one another and pasted together near the fold. Their distinctive characteristic is that the pages that are glued together open only partially whereas those that are not open fully. The set of books known as the Sanjūjō sasshi which the famous monk Kūkai brought back from China in 806 were bound with this method. It is believed to be the most ancient of the book-style formats. Its main shortcomings are that the glue tends to come off easily and that books in this format are prone to being eaten by insects. (See Below)
Because of these problems, the method fell out of favor after the 13th century (the Kamakura era, See below), with the exception of the Shingon sect of Buddhism, which continued to use it into the modern period. Books in this format are also counted in booklets (jō).
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