Boiling the Saltpeter

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

So 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.

There 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.