Making Saltpeter: A photographic essay

April 19, 2009 at 7:48 pm | Posted in Blackpowder, saltpeter | 2 Comments

Making Saltpeter: A photographic essay, Part One

saltpeter-bucket-hole To create saltpeter I began by using the instructions set down in The Pirotechnia of Vannoccio Biringuccio, a sixteenth century text. He tells the reader to take a cask and drill a hole in the bottom “as large as a grosso”. The translator noted that a gross was a coin about 22 mm in diameter. Therefore my first step was to drill a hole in the bottom of my bucket. I would have liked to use a wooden bucket, as that would have been more period, but wooden buckets are fairly expensive, and it would be a shame to ruin one with a hole in the bottom, even if I owned one in the first place. So plastic it was.

I did not have a drill bit that was exactly 22 mm, so I used one that was 3/4 of an inch, which was extremely close to the same measurement.

saltpeter-filter Next, Biringuccio says to “put a little thin cloth…[to] act as a strainer…”. I hunted around in my stash of fabric and found the thinnest, most open-woven cloth I could discover. It appears to be from an old set of curtains. I’m not sure what the fabric is made of, but I’m pretty sure it is synthetic. Unfortunately, all of the natural fiber material in possession has long ago been made into something useful, so I did not have any linen or wool pieces large enough to serve my purposes here. Even if I did, I suspect the weave would have been far too tight to make a practical strainer. I cut out a rough circle by laying the cloth over the end of the bucket and cutting around the edges.

manure-bucketBiringuccio gives two options for the next step, either to mix everything together at once, or to layer the ingredients. I chose to layer the different materials. The first material is “manurial soil”. He specifies that the best saltpeter comes from “animal manure transformed into earth in the stables”, and should be “powdery” for the best results.

With three dozen chickens in my backyard I did not have a problem coming up with manure. It’s transformation into soil was only about half to three-quarters complete, but I decided this was better than completely fresh manure. It was not powdery dry, but since it is April in New England, nothing is powdery dry. I did have the foresight to spread my manurial soil with plastic bags, so last night’s rain did not make the soil any moister than need be.

The instructions say to put a palmo of soil into the bucket. A palmo is about 11 inches. After measuring the bucket and estimating how much space was going to be taken up with the other ingredients, I decided to halve all of the materials, or else the bucket would overflow, spilling manurial sludge all over everything, which I generally considered to be a bad idea. For that reason, I used about six inches of manure.

ash-bucketThe next layer was a combination of three parts ash to two parts quicklime. Of the ashes, Biringuccio says to preferably use”cerris or oak or some other ashes with a sharp, strong taste”. I obtained the ashes from a friend with a wood stove, so I am not entirely certain what sort of ashes they were, and I wasn’t quite brave enough to taste them. (Where is a toddler when you need one?)

For the quicklime I used limestone I bought at a garden store. One or two ditos, or about one or two inches was called for. I used one inch or so.

Biringuccio suggests layering these items until you get to a palmo of the top of the cask. I only had enough room for one layer of each. He then instructs the reader to fill the remaining space with water and let it drain down into a container. I accordingly poured quite a bit of water into the bucket, and let it start to drain.

At first it drained quickly. But then I started running into problems. When I’d originally put the hole-bucket on top of another bucket to collect the water, I hadn’t been bothered by the fact that the buckets nested. But almost immediately after actually pouring the water, it suddenly occurred to me that water in the second bucket would create a suction, and I wouldn’t be able to get the buckets to come apart. This, sadly, proved true. I engaged the help of a friend, but we couldn’t get the buckets apart, even after we poured the undrained water out. We had to dump all of the contents into a third bucket to pull the buckets apart.

This required essentially starting over. I propped the hole-bucket up this time, and fished out my filter, now covered in filth, and replaced it at the bottom. Since I knew that there was a non-layered method, I decided that the dumped-together mess of my original layers was not going to effect my progress, so I dumped all of the ingredients back into the hole-bucket at left the slurry of water, ash, manure, and lime to drip into the lower bucket.

bucketsSo far it continues to drip…but very, very slowly. Biringuccio says to take the water and run it through the mixture a few more times. At this rate it’s going to be all week before I’ve managed to run the water through a single time. I think that once I’ve got this particular pass through finished, I am going to empty the hole-bucket and drill some more holes, hopefully speeding up the draining process. I might try to track down something better to use as a filter. Cheese cloth might be a better choice.

Since I don’t know how long it will take to drain, and redrain, and redrain, I can’t tell you when to expect Part Two of our amazing saltpeter adventure.


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  1. If these are the ashes I gave to you, they are mainly from oaks. We o burn a bit of maple, but these must have come from the last set of logs, and those were almost all red oak.

  2. Excellent. They are your ashes, which is great because Biringuccio specifically says that oak ashes are the best ones to use.

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