Of course you didn’t have to be a Colonial recycling specialist to make use of leftover fat and ashes. For those dirt poor and/or industrious types, there was always do-it-yourself soap making.
Now me, I’m descended from city folk mostly. But living in Louisville as I now do I’ve heard more than a few stories from country folk about what it used to smell like when their neighbors made soap. But why would it be so? Potash (or lye, which is even easier to make yourself) isn’t particularly smelly stuff. Neither is animal fat if it’s freshly butchered. Ah, but then what if it isn’t? What if the animal fat you’re using has already been used for cooking? Kitchen grease, poured off and stored just like the stuff that’s in that tomato can under your sink? Only it’s not a tomato can, it’s a barrel, and it hasn’t been accumulating for a week, it’s been there a year, since the last time you made soap.
Oh yes, rancid, cooked-with fat can also be used to make soap. And it frequently was, darned stanky soap. But if that’s all you had then it’s all you had, and soap making is too involved a process to bother with every time you pour off a little spent pork grease. And so once a year, usually in the fall, it was boiled up in a pot on the back 40. Water was added, the bits of meat and cooked gunk sank, and the fat floated. The whole pot was then cooled, and the “purified” fat skimmed off. The fat was then boiled again with lye, and the chemical magic called saponification occurred, in which molecular fatty acid molecules break apart and fatty acid salts, otherwise known as soap, were formed. If you were well enough off to have spare table salt on hand you tossed some of that in the pot to make cake soap. Otherwise you just used it as it was, a viscous liquid, one that was worlds away from Palmolive, at least odor-wise.
Neat. But Lord the whole thing caused a stink that wafted on the wind for miles. Fortunately, they outlawed it in the suburbs years ago.