Worldbuilding: Cleaning Up an Isekai

Part of the fun of any isekai is watching the characters try to find or recreate aspects of their home world they miss. (It’s truly amazing how many Japanese isekai worlds somehow have cacao for chocolate.)

Granted, if you’re working in a pure fantasy world, you can put what you like in it. But if you’re playing it in a harder mode – time travel, say, or a fantasy world based on our own history – you have to get a bit more creative. Especially when it comes to soap.

I know it’s worldwide these days, but soap as we know it (fats and oils saponified by mixing with potassium or sodium hydroxide, AKA lye) is a European cultural thing. Historians argue over whether the Celts or ancient Romans came up with it first, or if they both did. Given during the time period in question some groups on the Italian Peninsula were either Celts or mixed, I think the point is kind of moot.

What historians can mostly agree on is that soap got established, spread during the Roman Empire, took a serious hit during the Dark Ages, and rebounded from the Renaissance on.

Note that there are people who consider the Dark Ages’ reduced amount of bathing and overall hygiene as being due to a fanatical Christian preoccupation with matters of the body as evil. This view is at best ignorant. First, a key part of Roman cleanliness was public baths… which took a serious hit when epidemic diseases like smallpox kept raging through. Second, one of the major problems for everyone in the Dark Ages was finding enough calories. In straits like that, what would you do? Devote edible fats and oils to soap, or fall back on the less effective sudsy and otherwise inedible plants for cleaning? Third – soap-making requires specialized knowledge of how much lye and water to add to which specific kinds of fats at exactly what temperature. Not to mention how to treat the fats so they won’t go rancid before they’re soap, how to protect yourself from caustic lye, and how to tell if a batch gone wrong can be rescued with a little melting and tweaking, and when it’s safer just to throw the whole thing out.

These days we have written instructions, purified fats and oils, and online lye calculators, so your average careful person can make batches of soap at home. Prior to the printing press, most or all of this had to be in someone’s head. Lose a master and an apprentice or five in a Viking raid, lose even one critical step that keeps you from burning your own skin off, blinding yourself, or searing your lungs with the fumes, and soap-making goes bye-bye. No fanatics need be involved.

Which is bad, because besides the obvious morale boost of keeping clean, simple hand soap is one of the best low-tech antiseptics available. Bar none.

So a sane isekai protagonist with any knowledge of history is likely to want some. But how do you get it, in a culture that historically doesn’t have the practice?

Three options I see. First, figure out how to make it yourself. Risky but possible, if you have a lot of time and resources to dabble with. Second, and probably more practical, find someone local who works with the ingredients in soap (fats and lye) and try to explain what you want and what you know about how it’s made. Passing it off as “a tale from a mystical far-off land” optional. Third, see if there’s any way to make friendly or at least trade contact with a culture that does make soap. And bargain!

…Yes, these are all ideas I plan to use in Colors of Another Sky. There is a lot of modern medical knowledge Jason wants the people he’s with to have. Antibiotics would be awesome. Vaccines likewise. Yet those take time and knowhow he may not have or be able to leverage out of the surprising things cultivators know.

But soap? Soap may be doable. And handwashing saves lives.

A hero’s gotta start somewhere.

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