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.


55 thoughts on “Worldbuilding: Cleaning Up an Isekai

    1. Or a complete archive of the _Grantville_Gazette_. 🙂

      Not entirely kidding, though. The *fact* articles were written by people who *really* got into the weeds about what was doable with 1600s resources and 21st-century knowhow. Pressing LP records, steam power, *AM radio*….

      The key point of having the GG with you is that it’s not just a copy of WikiPedia or a hundred years’ worth of Britannica, it has a lot of critical links between the raw academic information and down-time application thereof.

      Speaking as an engineer who’s often toyed with the isekai idea, I’m often humbled by just how *little* use most of my skills would be in a medieval setting, especially without any of my reference materials (or Google). But, that said, even without the “Handy Dandy Isekai Protagonist Starter Pack”, Jason probably still knows the general outlines of how the smallpox vaccine was first created, or penicillin. And if he can share that idea with a skilled Healer-type in Magical!Korea, that could still be the critical clue that kicks off the vaccine and antibiotic revolution. (not to mention Jason would be aware of the risk of resistant bacteria from overuse of antibiotics)

      Liked by 3 people

      1. Remember that while variolation was so commonplace that the term exists, it was also dangerous. In a controlled experiment in Boston, 300 subjects got the treatment, and six died. Which was enough to make it very popular.

        Liked by 2 people

  1. A good water supply might be easier to start with if it didn’t exist as almost everyone realize that large amounts of good clean water is beneficial. There is a theory that civilization started with the need to build and maintain irrigation systems. Monument works like Stonehenge only require people to get together once a year if that, irrigation ditches and dams require constant work. Its fairly easy to explain the need for aqueducts and water towers. Also if you can only make a small amount of soap start using it as part of a medical treatment for wounds and skin problems.
    Once a water supply has been created little things like sand water filters for drinking water can be created. A good sand filter can prevent cholera and reduce parasites.

    Liked by 2 people

  2. There were other soap-like substances. Olive oil and a scraper, of course.

    The poorest early medieval Irish seem to have had bathhouses, even if it was a little sod house/sauna out back; and “sleic” soap was pretty common. The rich, both men and women, also had oil and pleasantly smelling herbs for anointing themselves after a daily bath.

    The rich combed out, curled, and styled their hair every day; but even a slave woman had a comb, which was legally one of the essential household items that could never be taken away from her. Ascetic monks and nuns combed and styled their hair too, so it was deemed important. (And probably helped prevent lice. And kept knots out of curlyhaired people’s hair.)

    But the Irish economy ran on herd animals, and there was plenty of water and plenty of peat for burning (as well as thick forests in earlier times). And the damp climate there made daily hot baths important, much as in Scandinavia and Slavic countries.

    The richer Irish just kept a bathhouse fire going all the time, by preference, which is easier if you are dealing with a separate house out back with its own peat fire. It was probably used for laundry too, in rich households, at the off-peak times when people were not bathing.

    (The literary convention was that you washed your hands in cold water from a well or stream at the start of your day, and bathed when you came home at night, before dinner. Hospitality to travelers and guests required getting them a hot bath and hot food when they were stopping for the night.)

    Liked by 5 people

    1. Come to think of it, fosterling kids in noble households were pictured as having two sets of clothes, so that they could wear one while the other was being washed. So laundry must have been earlier in the day, on days it was being done, which goes along with the non-peak times.

      Liked by 4 people

    2. Okay… It looks like originally “sléic” meant potash. But they were using it as soap after mixing it with stuff. Also, one of the words for some kind of rouging cosmetic was sleic no ruamhnae, so sleic must have been goopy or powdery.

      But yeah, the Irish had rouge and eyeshadow for both men and women, and even monks used it for whatever reason (maybe against glare, since they traveled around a lot during the day, and they were pale).

      Liked by 3 people

  3. Forget chocolate, the one that make me wonder is all the Japanese isekai protagonists that somehow develop soy sauce.

    For reference, soy sauce is a fermented product.
    Which means several months with specific bacteria, in specific climate conditions.

    The protagonist usually makes a lifetime supply from one bag of soy beans in a few hours by borrowing someone else’s kitchen.

    Liked by 6 people

    1. Yeah, that is weird. Although there are probably “quick pickle” ways to do a sort of soy sauce.

      It wouldn’t be salty, though, unless you lived really close to the coast or something. Maybe put dried seaweed in it for salt?

      Liked by 4 people

  4. Apparently a lot of “don’t have soap” people historically used saponin-containing plants.

    And today I learned that a lot of indigenous peoples will.poison fish by dumping soapwort into the water, and then they will clean and eat the dead fish.

    Liked by 5 people

  5. This view is at best ignorant.

    :long string of characters:


    The ‘dark ages’ are, properly understood, “we have no light to see, here”- and monday fridays take it to be “we see nothing, so nothing is there!”

    Liked by 6 people

    1. Distilling it to make the alcohol more potent and/or pure would take some doing, but 1600s is late enough that everybody might have invented distilling by then.

      I’d look up what you can make by distilling previously fermented rice wine, but I’m too lazy.

      … I wonder if you need copper for a still or if you could rig one up using bamboo… and how much it would poison the final product if you did…

      Liked by 4 people

      1. I can bid in with this because we’re fumbling through it-for funzies- freezing stuff and pulling iced stuff out is a good way to get higher alcohol, that’s teh origin of brandy.

        Liked by 3 people

      2. Everyone’s thoughts on “distilling” seem to go straight to “stills” and moonshine, when that’s nowhere near the only method of distilling. Depending on the material being distilled, sometimes that’s actually the hard way. You can distill some stuff with vacuum, others with freezing, others yet with heating (and it’s three entirely different forms of heating-based distillation to do it by heating and then siphoning out the right level, vs vaporizing it and collecting the condensation, vs vaporizing some of it and keeping what didn’t vaporize), or a half dozen other methods. And no, copper is _not_ needed for any of those, at least in a “the process inherently requires it” manner. It is, however, needed for some of those _for working with specific materials_, due to specific heat transfer and timing requirements for the process for the specific material being distilled.

        Liked by 1 person

    2. Alcohol has the same drawbacks as soap. You make it from food, so need a surplus of grain, or potatoes, or milk. One of the nice things about alcohol is it can be made from a whole variety of substances. But you are going to have to take a barrel of beer from someone to make a small amount of alcohol and you have to have the still. I think Korean metallurgy is good enough to make a copper still. I don’t know about glass. Glass industry would be well worth encouraging

      Liked by 3 people

      1. Tobacco spread the fastest of any New World crops. Even faster than the useful potato. People like some mind-altering stuff, even as simple as tobacco as an anti-depressant.

        Liked by 2 people

      2. A check on Wikipedia says that the Koreans had had distilled alcohol since the 940s. If true, and if it was fairly common that would be a posssible disinfectant

        Liked by 2 people

  6. Jason is probably going to be working on the soap issue way before the “Must have Chocolate” because as nice as it is to have Chocolate, being consistently clean is much more important.

    As in, before he realizes that he and his companion might be in an alternate history.

    Not only is it important to your health, but it is also much easier to keep your view of the world as “Glass Half Full” rather than “Glass Half Empty”.

    Liked by 2 people

  7. a) Obviously everyone has to be carrying, at all times, at least three computers with more or less the same documentation on a wide range of technologies. To include the basic tools to make tools textbooks. Also, memorize everything needed to reinvent everything for the replacement power supplies.

    b) Isekai is often overlooking the opportunity to have food stuffs produced from entirely different domestication pathways from our own mainstream staple crops.

    c) You could go really over the top with b, and the ‘isekai transportee as shaman’, if the psycho-active components of common ‘special use’ herbs are metabolized different by the transportee, even compared to local humans, because of the equivelant of tens of thousands, or hundreds of thousands of years of differences in natural selection as applied to metabolism.

    d) I think vanishingly few Japanese LN isekai transportees ever ‘invent’ nukes. Technical details are of niche interest, there are a lot of controls, and how would you even plot that without being boring, and without making your otherworlder carry the idiot ball.

    Liked by 3 people

      1. May read as more snarky than I intended.

        Imagine someone who believes in routine concealed carry, and in practicing tactical thinking in daily living, commenting on the practicality of someone else’s boasts about how they never sit, it is always a ‘tactical perch’, and how their every motion is tactical and super excellent. A hyperbolic version of the latter would be someone reporting that they maintained perfect situational awareness, and readiness to respond, while spending weeks in a coma.

        I forgot to think about what you would want stored on microfiche, and what on more normal film. Properly integrating that into your everyday carry could make international travel a wee bit difficult. “No, I’m not smuggling technical information. I’m prepared for the contingency of being sent to another world.”

        If I were sent back in time to WWII, I could possibly explain enough about wall AC to supply a charger to supply a phone. I don’t think I’ve ever properly built a good dataset and loaded it onto my phone.

        I tend to keep the information content of my everyday carry pretty sparse, so I don’t get too confused about what I am actually trying to do.

        Comes to mind that someone who does prepare ‘properly’, carrying incomplete databases with /some/ fallbacks for access, is the type of person who if transported would immediately work on preparing a fall back with more data for their next transport.


    1. I believe I know of exactly one Isekai story that involves creating a nuke. What I know of said story overall makes me want to tear my hair out–I’m not sufficiently knowledgeable about the technologies involved, but how the inventions are _used_, along with the societal stuff, just has me shaking my head at the cringe writing.

      (High School Prodigies Have It Easy Even In Another World, to be precise. I tried to watch the anime adaptation and dropped it in a hurry. Just another Isekai with protagonists who are overpowered to the point of being boring.)

      Liked by 1 person

      1. …I didn’t even know about the cannibalism. Yeargh.

        Is it me, or is Isekai going increasingly bizarre in the name of standing out in the hugely-overcrowded genre?

        Liked by 1 person

      2. yes


        Part of it is a residual effect, with more bizarre webnovels that previous investors skipped. And media investors are also not necessarily great people.

        Some ‘WTF’ reaction is simple overexposure to a genre that clearly had a bubble. Other ‘WTF’ reaction is clearly to crud stories written by authors with deficiencies as artists or as human beings.

        Liked by 3 people

      3. I can think of two, offhand. One was where a “cutting spell” is easy and not very energy-intensive, but the isekai protag is the first person to ever have the mental concept of cutting/splitting *atoms*… and nearly scares themselves to death when they realize what they have now.

        The other is one of Rick Cook’s series where magic turns out to work a *lot* like computer programming, which lets the displaced computer geeks *literally* hack the universe. And one of them builds a spell to take a pint of water and squeeze it without any upper (lower?) limit. Instant H-bomb.
        (I miss that series. It was so sad when Cook lost his writing mojo after surgery)

        Liked by 2 people

  8. If you look at the Outlander series it shows some of the problems of introducing new techniques even when going back a short time — 300 years — and the same culture. The heroine had trouble persuading people to eat tomatoes and cooked greens among other things. Ether was know as an anesthetic but hard to obtain.

    Liked by 1 person

  9. The Shinigami Detective series kinda sidesteps that a bit. Jamie knows the inventions exist, and has a vague idea how they work. She gives ideas to a literal genius inventor and innovator, and then steps back. Noticeably, the tech level I think is either Victorian or Edwardian. After awhile, she can get schematics and things from Earth, and promptly does so.

    One of the very first things we know she requests? Rubbing alcohol. As a disinfectant. Because they did already have soap.

    Liked by 2 people

  10. On a semi-related note… I’m really hoping for Jason, once he realizes his historical knowledge is, perhaps not *wrong*, but definitely less reliable than it *should* be, has a moment:

    “…this must be what Wrong Genre Savvy feels like.”

    Liked by 2 people

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