Recall that in the last post, we said that soldiers would carry a slow burning rope tied around the waist, so that they could light their crude firearms quickly at any time. This special rope or cord is called a slow match or match cord.
The origin of this term has to do with the Greek word mixa (the word for "lamp wick"), which was adopted by the Romans and became mica, which in turn was borrowed by the French and became meche, which became the English word match. In the late middle ages, match cord was the only way to carry around a quickly available source of fire. In fact, when matchsticks were invented, the term "match stick" itself originated from the fact that it was a replacement for "match cord".
So what is this "match cord" or "slow match" made of? The original match cords were made of hemp or flax fibers. Remember that at this time, cotton was a luxury item in the west and people only knew that it came from a plant somewhere in India. As late as 1350, Sir John Mandeville wrote in his famous book of travels that "There grew there [India] a wonderful tree which bore tiny lambs on the endes of its branches. These branches were so pliable that they bent down to allow the lambs to feed when they are hungrie." So obviously, cotton was out, and the cheaply available hemp and flax fibers were the materials of choice to make the cord.
So how would they ensure that the cord could burn slowly for a long time without going out? The first step is to treat the cord in lye (Potassium Hydroxide). The reason for this is because unprocessed plant fibers normally contain a lot of lignin, which produces most of the ash when the cord burns. In order to reduce the amount of lignin, the cord would traditionally be soaked in a lye mixture. A lye solution is traditionally produced by taking a barrel, filling it about halfway with ashes left over from burning firewood and filling the rest with water (usually rainwater was used for better quality lye, since it is relatively purer compared to other sources of water). After letting it sit for a few days, the liquid from the barrel is filtered through a cloth filter and this is the lye solution. The rope to be prepared is put in this solution and the whole is boiled for about an hour. The rope is then taken out and rinsed in water until the rope can be placed in a pan of water without discoloring it. This means all the extra lye has been washed out of the rope. As an additional precaution, a little bit of vinegar (acetic acid) would sometimes be used in the final rinse to neutralize any remaining lye.
Next, the rope would be treated with a saltpeter solution. Saltpeter is essentially potassium nitrate (KNO3). Sodium nitrate (NaNO3) was also used sometimes, but potassium nitrate is less hygroscopic (i.e. it doesn't absorb moisture from the atmosphere as much) and thus became the chemical of choice. The traditional way to make saltpeter in Europe during the middle ages (since it wasn't available as mineral deposits as was the case in India and China) was to use urine. The urine was placed in a barrel containing straw and allowed to sit for a few months until it turned "sour". Sometimes manure was used as well. Urine from monks was considered to be of better quality, with the urine of bishops being the best of all. The resultant was then washed with water to extract the chemical salts and filtered through wood ash. The solution could also be crystallized by drying in the sun, if it was desired to use the saltpeter crystals for gunpowder manufacture. In the case of making match cord, the solution was used and the treated rope from the previous step would be soaked in the solution and left for a day or so. Then the cord would be taken out and dried in the sun.
The resulting match cord burns very slowly, but has some resistance against being put out by humid and foggy conditions. A length of match cord would usually be wound a few times around a person's waist and both ends would be lit as a precaution and left to hang from the person's belt. That way, if one end was accidentally put out, it could easily be re-lit using the other end. A soldier could therefore walk around all day carrying his crude firearm and always have a source of fire ready to be used at short notice.