About Slow Match

Early guns were set off by igniting a bit of powder at the touch hole, so there was a need to have a convenient bit of fire handy. What they used was slow match, also called matchcord. European slow match was first shown in a 1411 manuscript; prior to that, guns seem to have been ignited by a red-hot poker.

MAKING SLOW MATCH
Slow match is made by soaking rope in a nitrate solution, then letting it dry. It burns slowly and evenly despite wind and rain. Well, wind, anyway. The match is lit, and put into a small clamp on a pivot on the side of a gun. When the trigger is pulled, the clamp moves to push the match into the priming powder, which sets off the priming powder and the main charge. The flash of the priming powder does not put out the glowing coal on the match, though it often blows the match out of the clamp.

Historically, the sodium nitrate was extracted from urine (ugh) or gleaned from underneath manure piles (double ugh!). Today, we can use either sodium nitrate or potassium nitrate. I have used potassium nitrate (KNO3), largely because that's what they had at the chemical supply house at the time (though I've also heard it's better because it absorbs less water from the atmosphere).

The medium for the nitrate solution was either water or vinegar. I have heard several exponents of both mediums, but never an explanation of why one was better than the other.

At any rate, when you put the matchcord out to dry, you want to lay it out flat. If you drape it over something like a clothesline, the solution will drain towards the ends of the match, resulting in low nitrate concentration in the middle, and high concentrations at the ends.

High nitrate concentrations means it burns faster, which is bad, and makes is spit more, which is also bad. "Spitting" is when little bits of hot nitrate pop off, and they can cause quite a surprise if they spit off into your priming pan.

From Webster's Revised Unabridged Dictionary
{Slow match}, slightly twisted hempen rope soaked in a solution of limewater and saltpeter or washed in a lye of water and wood ashes. It burns at the rate of four or five inches an hour, and is used for firing cannon, fireworks, etc.