The Manufacture and Preservation of the Tripitaka Koreana Woodblocks
Park Sang-jin, wood anatomist and professor emeritus of Kyungpook National University
The Tripitaka Koreana woodblocks are not beautiful works of art. They simply appear to be wooden tablets carved with countless characters and covered in black ink. They are, however, a massive and intricate relic of print culture that contain the tenacity and devotion of the people of Goryeo, who carved one by one the 52 million characters of the Buddhist sutras. Even a trained artisan can only engrave about forty characters per day. Thus it is estimated that some 1,300,000 artisans were mobilized for the task of engraving the Tripitaka.
Humanity was able to enter into civilized life because it developed the technology to record knowledge in writing and to preserve and convey this knowledge to others. At first, human beings wrote letters and drew pictures on animal skins, cloth, clay tablets, and tree bark. When the technology developed a little further, they used thin strips of bamboo and wood as well. As Buddhism spread, there was a keenly felt need for the printing of sutras that everyone could read at once. If characters were carved into wooden tablets, large-scale printings could be made whenever needed. Korea developed printing technology very early on; by around the 8th century, Korea already possessed what is now the world’s oldest printed text, the Pure Light Dharani Sutra, which was printed from woodblocks. After this, the full blossoming of woodblock printing technology came with the Tripitaka Koreana woodblocks. They are the largest set of sutra woodblocks remaining on earth today.
The wood and manufacturing process of the sutra woodblocks
The Tripitaka Koreana woodblocks consist of 81,528 wooden tablets engraved with sutras that comprise some 52 million Chinese characters. A single woodblock is engraved with around 640 characters, and handles are attached to each end for convenience during printing or storing. They vary in length, but most of the woodblocks are 68 or 78 centimeters long. They are 24 centimeters tall and approximately 2.8 centimeters thick, and they weigh about 3.4 kilograms each. If all the woodblocks were to be stacked together they would tower 3,200 meters into the air, and if they were laid end to end they would stretch for approximately 60 kilometers. Their total weight is approximately 280 tons, and they take up an area of approximately 450 cubic meters.
After taking minute samples from the woodblock and examining these under a microscope, it was determined that 64% of the wood used in the manufacture of the woodblocks came from sargent cherry trees and 15% came from sand pear trees, both of which are common in southern and central Korea. The remainder of the woodblocks are made from costata birch, giant dogwood, painted mono maple, thunbergii camphor, and david poplar, each accounting for anywhere from 1-9% of the woodblocks. Sargent cherry trees, which account for most of the woodblocks, produce even quality lumber and have a specific gravity of around 0.6, making them ideal for engraving, and they are relatively common in places easily accessible for logging.
The first step in the manufacturing process is to cut down trees of at least 40 centimeters in diameter, and these are left in the mountains for one to two years to relieve any growth stress remaining in the trees. Two-person teams then cut the trees with a gang saw, leaving behind the ends and taking only the wooden tablets with them. In order to reduce the risk of splitting or warping during the drying process, the tablets are gathered together and boiled in salt water. After at least six months of drying in the open air, the surfaces of the tablets are made smooth with a plane. The tablets are trimmed to the size of sutra woodblocks, and then handles slightly thicker than the woodblock itself are attached to both ends. These handles prevent the engraved portions of the tablets from touching when stacked or placed next to each other, and they also prevent warping and make it easier to handle the woodblocks when storing or printing.
Next, Korean paper on which the text of the sutras has already been written with a brush is placed on the woodblocks in reverse. When the ink dries the characters are difficult to see through the paper, so the paper is brushed with vegetable oil as the characters are engraved. Brushing an engraved woodblock with ink, placing a piece of paper on top, and then lightly tapping the paper will print the engraved sutra on that piece of paper. After several printings, some of the woodblocks were varnished with lacquer. The lacquer tree, whose main component is urushiol, is a traditional raw material for painting in East Asia. Lacquer prevents the absorption of moisture and is thus used as a preservative and insect repellant, but seeing as how only some of the Tripitaka Koreana woodblocks were varnished with lacquer, it would seem that this was done for decorative purposes.
Even a trained artisan can only engrave about forty characters per day. Thus it is estimated that some 1,300,000 artisans were mobilized for the task of engraving the Tripitaka. The actual manufacturing period is known to have been 16 years, according to records in The History of Goryeo. But according to notes engraved in the woodblocks themselves, they were engraved over a period of 12 years, from 1237 to 1248. Thus some 110,000 artisans were mobilized each year. The number of woodblocks engraved each year differed, so in certain years the number of artisans mobilized would have reached several hundred thousand.
Excellent natural air circulation
Despite the fact that wood is susceptible to rotting, insects, and fire, the woodblocks have been preserved without damage for 760 years, thanks to a variety of scientific measures. Let’s first look at the structure of the buildings used to store the woodblocks.
The wood block halls are wooden buildings arranged in two rows 16 meters apart, each 646 square meters in area. They are arranged facing south and so receive a good amount of sunlight, ensuring that the buildings are constantly filled with dry air. The interiors of the wood block halls are devoid of all unnecessary decorations and designed to allow the smooth flow of air. Crossbeams are supported by the exterior columns, and these crossbeams are fixed through the central columns of the building. Each crossbeam is then supported by smaller columns on either side of the central columns, making for as wide a space as possible inside the building.
In addition, the upper and lower windows in the woodblock halls are different sizes in the front and rear of the buildings. Since humid air sinks, the rear windows on the north side of the woodblock hall are designed so that the lower window is slightly smaller than the upper window, allowing less humid air into the building. Once the air is inside the building, it absorbs the moisture from the woodblocks and sinks to the ground. Thus the lower windows on the southern side of the buildings are over four times wider than the upper windows to allow this humid air to escape more quickly. Since the drier air rises, the upper windows on the south side are very small to keep this dry air inside the building for as long as possible.
The floors of the buildings are not covered but left as bare earth. Dirt naturally maintains a constant level of humidity inside the woodblock buildings, absorbing excess moisture and preventing dampness depending on changes in the air humidity. However, during recent renovations, the surface of the floor was covered with a thin layer of hardened quicklime to prevent dust from arising. This layer of quicklime could block the exchange of moisture in the earthen floor, preventing the regulation of moisture in the woodblocks, so this measure needs to be scientifically and comprehensively reexamined in the future.
Another secret to the preservation of the woodblocks is the method by which the woodblocks are stored in the woodblock halls. The halls house long rows of shelves for the woodblocks that run the length of the buildings. There are a total of five vertical shelves, and the woodblocks are placed on these shelves broad side down. The shelves are further divided horizontally, and each shelf section contains two rows of woodblocks, for a total of about 80 woodblocks per shelf. The woodblocks themselves are 2.8 centimeters thick and the handles are 4 centimeters thick, so if the woodblocks are seen from above there is a rectangular space between adjacent woodblocks measuring 2.4 centimeters in width and 60-70 centimeters in length. When seen from above, the five vertical shelves resemble a square exhaust stack. This is a natural circulation device that allows air within the woodblock halls to move vertically according to convection currents. At present, the water content of the woodblocks remains at around 16-17%, with very little seasonal change. This is because primary consideration was given to the circulation of air when the woodblock halls were constructed and the shelves arranged.
The layers of ink that dried on the woodblocks after they were used for printing are also a great help in the preservation of the woodblocks. The wood of the woodblocks is covered with numerous minute openings, and the large particles of the ink block these openings and remain on the surface of the woodblock even after printing. Thus the woodblocks are left with a coating of ink after printing, and this layer forms a film of carbon on the surface of the woodblocks. This carbon film delays the aging, weathering, and decaying of the woodblocks due to heat and light, and even helps to block some moisture as well.
Even if the woodblocks are preserved by such scientific designs, there can still be accidents such as theft or fire. The first crisis came in 1592, when the Japanese invaded Korea, but the righteous armies stopped the approach of the invading troops. Again, in 1950, during the Korean War, orders were given to bomb partisans occupying Haein Temple, but the air force colonel in charge made a wise judgment and instead attacked a different area with machine gun fire only, thus averting catastrophe. More than anything else, the Tripitaka Koreana woodblocks have remained in such a pristine state over the long period of 760 years thanks to the efforts of the monks who have devoted themselves to protecting them.