Boiling the Saltpeter

June 12, 2009 at 11:32 pm | Posted in Blackpowder, saltpeter | 3 Comments

saltpeter boiling 001So the next step in the great saltpeter adventure is to boil the saltpeter down. Biringuccio instructs us that once we have liquid “saturated with a great deal of saltpeter” by all of the previous work with water and manurial soil, we should then boil that saltpetery liquid “very slowly until it is reduced by about a third. Then it is removed and put to settle in a large covered vat.” Okay, boil liquid. This I can handle.

Since I would be boiling liquid that was infused with manure, I decided that it would be in my best interests to do this outside of the house. Therefore I dug out my handy camping stove. After some dithering about whether I would use my rather-small-but-already-contaminated-with-grossness dyeing pot or instead just go whole hog and use the giant lobster pot, my extremely accommodating husband convinced me to use the lobster pot, since we don’t generally use it anyway and it would be a lot more convenient.

saltpeter boiling 004There was some procedure-based dithering as well. After talking about boiling the liquid, Biringuccio then tells us to let it settle, then boil it a second time. He then goes on to say that “Each time it boils, it forms a foam and swells up so much that if one is not watchful…much that is good is carried away” and then gives instructions on how to prevent this using lye and alum. What he doesn’t make clear is whether to use this treatment the first time it boils, the second time, or both times. Since he talks about the treatment making the water clear, and then goes right into the last steps of congealing, I decided to interpret this as waiting until the second boiling stage, when the water is already partially clarified. I based this on the fact that my saltpetery water is a dark chocolately brown and I seriously doubt that even lye and alum is going to turn it clear after a single boiling.

So I boiled the liquid. I even managed to do so slowly. It did indeed foam, though not very much. (Should I take that as a bad sign and be worried?) After about two or so hours, and about 1/3 reduced (or halfway there), I ran out of fuel for my camp stove. The smell had not been nearly as bad as I had feared it would be. It wasn’t something I’d suggest as a perfume, of course, but neither would it send people shrieking from the room. I have a hood and fan over my stove, so I decided to just continue the boiling inside on my kitchen stove. I will say, in my defense, that I waited until after I had made dinner before bringing gallons of manure-infused water into my house to steam merrily away.

Having reduced the liquid to 1/3 of the original measurement, I was ready to “put it to settle in a large covered vat”. Biringuccio claims that once it has settled the water is “very clear [and] an earthy thick sediment that it contained is removed.” I remain doubtful that the water will settle enough that it will separate into sediment and liquid. After a week of sitting around settling it still looks like hot chocolate, albeit without the tasty aroma.


RSS feed for comments on this post. TrackBack URI

  1. […] of the smell it’s interesting. The first time I tried this, the liquid smelled awful, and then when I started boiling it, the smell changed to be […]

  2. Hi! I tried making saltpeter at home following Agricola’s instructions and stumbled upon this site while researching lye making. My biggest problem was unnecessarily delayed filtering and turbidity of saltpeter water. The best kind of filter that worked for me was layer of soft grass over the holes, than layer of washed sand. Grass stopped clogging with sand and sand provided the biggest possible surface for draining earth and ashes. I first tried to solve turbidity by inducing natural flocculants i.e. slaked lime. It did work but left extra lime in the water which again made it turbid with white. After learning that lime works by inducing positive ions into solution I reckoned that same could be done with potash lye. So i packed tightly layer of ashes over sand and let through earth leached water only and slowly it came out clear! I suppose muddy precipitate was instantly formed and trapped in the ash filter. It felt wonderful until I started boiling it because it again became hazy, but after a while and about half boiled out it became clear dark red with grey sediment in the bottom, just as Agricola wrote would happen. I let it sit for one hour, poured clear liquid off and boiled it to dryness. At the bottom remained brownish salt which tasted stingy and cooling athe same time which is what saltpeter is supposed to taste like, I mixed it with charcoal and it burned to my great delight. I used earth from an abandoned stable and there was very little foam while boiling, I didn’t use alum. Also I didn’t strive to purify it since the amount was only about 60 grams, if I make more of it I will attempt to recrystalize it.

    • Neat! I love hearing about other people’s experiences, since there are so few of us who are experimenting with these old processes. I didn’t quite have the courage to try tasting my saltpeter – the manure-laden soil I used was probably a little greener than it should have been.

      It’s amazing how well the home-made stuff burns when mixed with charcoal.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

Blog at
Entries and comments feeds.

%d bloggers like this: