This gunpowder recipe was transmitted from the Portuguese to Ōtomo Sōrin, who in turn informed Ashikaga Yoshiteru, who then bestowed it to Uesugi Kenshin. In contrast to the previous documents, which were secret in that they could only be opened by Kenshin, this recipe had no such protections. This document reveals that a sophisticated recipe could be transmitted from the Portuguese to the Japanese. The composition of gunpowder determined the power of an explosion and the distance that a bullet could be fired. Potassium nitrate, or saltpeter, provided the explosive potential, while sulfur lowered the ignition temperature, and carbon binded the other two ingredients. John Bate in 1634 characterized the ingredients as “The Saltpeter is the Soule, the Sulphur the Life, and the Coales the Body of it.” Early Chinese gunpowder recipes only contained 50-55% saltpeter, but in fifteenth century Europe, the ideal ratio of gunpowder was determined by the German general staff in the nineteenth century to be either 74:10:16 or 74:12:13 saltpeter to sulfur to coal. This recipe contains two options of 80:12:8 and 77:13:10, which closely approximates the ideal ratio. It also describes how to heat and mix the ingredients into a slurry, and dried, which was more effective than simply mixing the grains. Kenshin, after receiving this recipe, engaged in a series of attacks on his rivals, occupying Kamakura itself in 1560-61, and used guns effectively at the battle of Kawanakajima in 1562.
Charcoal one bu, two shu (12.5g)
Sulfur one bu (9.37g)
Potassium nitrate one ryō, two bu (56.25g)
Charcoal one bu (9.375g)
Sulfur three shu (4.6875g)
All of the highest quality
Among the used for making charcoal, the , or the are suitable. It is not good for the wood to be too dried out. Forty to fifty days is about right. Longer than that will result in the wood splitting apart. Old trees are not good. However, if the tree is a new sprout from an old stump then even an old tree is no problem. Cut the wood for charcoal at about one foot. Make sure you remove the bark. Remove the inner core, then dry the wood for a day. Since the sun of the summer is strong, it should dry out well in about ten, forteen, or fifteen days. However, if you dry the wood in excess of twenty days, then you should dry it in the shade.Next is the roasting of the wood. Dig a hole about two feet deep. Cut about five inches of straw and lay it down on the bottom. Pack the wood on top of the straw. Light it from below and when the wood starts to blaze, apply straw on top of the wood continuously to keep the blaze from dying down. If burnt well, smoke should not rise from the bottom. When the smoke does not rise in that manner, flip over a bucket and using it as a lid, steam the wood pieces. When they turn to charcoal, pour on hot water and let them boil a good amount. Then take them out and roast them. When they dry, they are ready for concoction.When making the best powder, this is how to make the charcoal. But not all charcoal needs to be done this way. [I.e. you can abbreviate steps to make a lower grade charcoal.]When cooking the potassium nitrate, for one catty of potassium nitrate add about nine cups of water. For that much water, remove an appropriate amount of wood [from the fire]. Reduce the slurry down to a third of the original amount. Then put it in a bucket with a diameter of one foot and store it away. Do not check it for one whole day. On the following day, check it. Put the top layer of liquid into a separate bucket. With the potassium nitrate that congealed on the bottom of the bucket, dry it for about a day. Once dry, scrape it with a spatula and thoroughly dry it again. Then with the former top layer of liquid, reduce it to half its original volume. When it cooks down, add one cup of water and let it come to a rolling boil again. Then as before, let the liquid cool in a separate bucket and repeat the process [of removing the top liquids, drying the bottom solids, and reducing the remnant liquids].Use bright yellow sulfur. The green sulfur is not good. If when mixed with sand and what not, scrape that off with a small blade. For a good concoction, as long as the color of the sulfur is good, it’s not a problem to have crumbly, clumpy sulfur. But firm sulfur is even better.Grind [the charcoal, potassium nitrate, and sulfur] on a mortar. If ash rises, whisk in some water, but without soaking the gunpowder. Mix the ingredients until you cannot see the sulfur.
Then put a bit of the powder on a table and ignite it. If there is no trace of powder remaining after the reaction, wrap the powder in paper. Additionally, wrap it in three layers of cloth. Seal it up very well, place it on a board, and using your feet, pack it together so that it becomes firm. Then cut it up finely.
Under no circumstances should you have open flames at the site producing the powder. If a fire breaks out, immediately a disaster will arise. Even when igniting the powder to test it, have no other powder nearby. It should be stored away separately. Fire can ignite powder even at a distance of two to three yards. There must be no negligence.
Though the aforementioned may have you believing that the process of making the powder takes a lot of time, once you get used to it, it takes no time at all. Even when you need to make about five or six catty, use the above ratios. On a roughly grind the three ingredients together. On a stone mortar — similar to a — blend them together. When ground to a fine grain powder, pack it into bamboo cylinders. Once hardened, split open the bamboo and cut the powder.
All the details not recorded here will be transmitted orally by Momii.
Eiroku 2 , sixth month, twenty ninth day
一 ゑんせう 二両二分
一 すみ 一分二朱
一 いわう 一分
一 ゑんせう 一両二分
一 すみ 一分
一 いわう 三朱