Welcome to Stuff to Blow Your Mind, a production of iHeartRadio.
Hey you welcome to Stuff to Blow your Mind. My name is Robert Lamb.
And I am Joe McCormick, and today we're going to do another baby looked at Me style topic. My daughter is ten months old now, and after I came back on the show, after I came back from parental leave, I think I warned you all that there would probably be plenty of baby looked at Me style content in the coming years. And this is one that has really harnessed my brain. It starts with an observation that I'm sure anybody out there who has or has ever had
young children will recognize. And it is what one might call anomalous adhesion syndrome, the sudden realization that an unusual surface in your house has become sticky and you don't know how it happened. I don't know. This is one of the anomalous phenomena that we need to resort to the proof of aliens confirmed column for. But I don't know. We'll see. And in my case, it starts with my child eating like a frozen fruit smoothie pop. Rob, I don't know if you ever made these in your house.
But it's a nice little treat, you know. You like blend up some strawberries and bananas and stuff and freeze it in the freezer with a little handle.
Yeah. Yeah, we have done this plenty of times. I think we've stopped using them though, but they're still in the freezer. I don't know when we filled the mold last, but they're still awaiting use.
Well, so you give one of these to a baby. You know she loves it, but no surprise that her face gets sticky. You would expect that her hands get sticky, the floor around her gets sticky. But then later maybe you're like pulling a book off the shelf and you notice that the underside of the bookshelf is sticky. How did that happen? We could insert the X files music
sting here, but I do have a hypothesis. At first it was a little more perplexing, but I think maybe it's that the adults in the house are acting as an intermediary or as a vector of stickiness from one surface to the other. So like during frantic moments of dealing with the baby, an adult is maybe getting stickiness from the baby on themselves, and then touching you know, the bookshelf, for the refrigerator door handle or whatever it is.
Hmmm, well, that's pretty good. I mean, on one hand, you could just say sticky baby touches everything, and then therefore everything is sticky. I still think that's a solid hypothesis, this transference of sticky. This also holds what holds up well. I think another possibility is heightened stickiness thanks to baby results in heightened awareness of stickiness, and therefore you're just more inclined to notice stickiness now that there is an enhanced stickiness culprit in the household.
You know, normally, I would say that kind of explanation makes a lot of sense, but I think for me, psychologically it's the exact opposite. I used to have much more awareness of the ickiness of stickiness, but now having a baby, I am I think I am somewhat desensitized to the to the icky of the sticky.
Hmmm. Interesting. Yeah, I mean we still seem like, I still feel like we have enhanced stickiness in the household even at this point. And I think part of it too is just like you get a third body in the house, or you know, in larger family households, you know, multiple more bodies, that's more folks coming in and out of the kitchen, that's more folks handling food. Yeah, there's just kind of this exponential swell of stickiness. And then how do you handle it? Do you just become desensitized
to it? Or do you try and keep up the battle against the sticky?
Keeping up the battle is really a slog because another part of you know, a baby learning to appreciate solid foods is a lot of throwing foods on the floor, a lot of the floor.
How did people cope with carpets, wall to wall carpets and children in the past. I don't know.
Oh, I don't want to think about it. But anyway, so this got my brain cranking on the subject of stickiness, and I wanted to kick off a series today exploring the concept of stickiness and it's many wonderful, terrible and mysterious forms. So one place I was kind of foiled right at the beginning is I was like, Okay, is there just an answer to the question, sort of a chemistry or material science question, what makes a sticky thing sticky?
I think it turns out this is one of those questions that seems like it should have a very simple answer, but in fact is rather difficult and complex, because while stickiness seems like one phenomenon to us, you know, we have a single word for it, it's actually a lot of different things. And I've been reading a book that addresses this a bit. It's a book called Sticky, The Secret Science of Surfaces, by Laurie Winkless from Bloomsbury twenty twenty three. So this is a new popular science book.
It's not just about stickiness. It's also about slipperiness and generally about surface interactions, and the science thereof is by this author named Luri Winkless. And for everybody who says that you know, book jacket blurbs don't matter, I will say this is a case where I was swayed. I was convinced to go ahead and buy this one because it had a positive blurb from Mary Roach.
Oh yeah, friend of the show Mary Roach. Always a ringing endorsement.
But anyway, in the introduction to her book, Winkless reveals something that kind of surprised me, which is that despite the fact that stickiness and slipperiness are essential and probably universally recognized properties of substances in the world around us. You know they have crucial and perfectly well understood everyday meanings. To quote from her introduction, the words sticky and slippery are also not true materials properties in the way that
say hardness and thermal conductivity are. They have no agreed upon scientific definitions and no specific metrics that can be used to quantify or compare them. Now, of course, stickiness and slipperiness do involve a number of well understood and mathematically well defined physics concepts like friction, viscosity, elasticity, and so forth. Apparently, they in themselves are kind of more vague and complex concepts, and they describe a number of
different phenomena with different causes. So when you say that glue is sticky, and velcrow is sticky, and sugar syrup is sticky, you're using one word to describe a similar property these substances have. But the explanations can go in a variety of different directions. So this exploration of stickiness over the next few episodes will not be a single straight highway, but a bunch of diverging roads. Though, I think because we started with the example of food based
substances getting on things and making them sticky. I think it might be good to stick to food for a bit.
Let's stick to the food for a bit, yes, Because, yeah, stickiness is not always a byproduct of misplaced or spilled food treats. Sometimes it's a vital part of the culinary experience. And as we'll get into this, might not be as obvious to all listeners out there when we talk about, oh, don't you love it when the food is sticky? Don't you love it when the food is chewy? There's actually some rather stark differences that can be observed across different food cultures.
Now, I'm sure when a lot of people think sticky foods, you immediately think sugar syrups and candy. But we're going to go in a slightly different direction here.
That's right, because you have most chewy and sticky candies. I mean, yeah, that's the sweet dimension. But the example we're going to bring up here, it can be enjoyed sweet, it can be enjoyed savory. I'm talking about the sticky food par excellence. Sticky rice. So you may have a counted sticky rice in different forms. I mean, there's like bamboo sticky rice, there's Oh, there's mango sticky rice, which
I think is absolutely amazing. You know, it's going to be different depending on you know, exactly what sort of mango you you have on there, but you can and sticky rice can be enjoyed with savory foods, it can be enjoyed with sweet foods. It's just absolutely tremendous.
Now, when you say the phrase sticky rice, you could just be talking about rice and using sticky as an adjective to describe the rice. Because rice is, as we'll discuss, different varieties of rice are a varying levels of stickiness. But there is also a type of rice that is specifically sticky rice.
That's right. Specifically, it's a Ariza sativa variant glutenosa, also known as glutenous rice. But don't let the name deceia view. It doesn't actually contain gluten. It is merely glutenous in that it is glue like or.
Sticky, also sometimes called sweet rice. The last time I bought it at one of our local Asian markets, it was just in a bag that had sweet rice written on it.
Yeah, and there are numerous cultivars of this particular type of rise and it's grown throughout Southeast and East Asia. This and the among the cultivars, you have mochigami, which is key to Japanese mochi, which is also one of life's great pleasures. Now where it gets interesting because ultimately the question arises where does the stickiness come in? What makes it stickier? So typical rice contains two starches, amelos and amelo pectin, but sticky rice lacks amelos and its
absence leads to this sticky quality that we have. This is due to a mutation in its waxy gene. DNA evidence suggests that it emerged a single time somewhere in Southeast Asia, and the resulting stickiness was seemingly light, preserved, encouraged. You know that we see this story time and time again throughout the history of domesticated and cultivated foods, where something changes in the particular plant and we realize, oh, this is even better than before.
Yeah, I can see that. In another way, I kind of think about a glutinous rice as blasting off of one end of the rice experience spectrum. So, just from personal experience in the kitchen, I'm familiar with the properties of different kinds of cooked rice, and there is a general pattern that longer grain rice varieties tend to be firmer and less sticky, so they stick to each other less.
So you think of the example of basmadi rice used in a lot of Indian cuisine and other long grain rice is they tend to have grains that separate from one another more easily and remain firmer after cooking. So these rices kind of flake when you toss them with a fork after cooking. Rob you know that experience.
Yeah, yeah, And of course this becomes vital too if you're going to be potentially eating with chopsticks. You know what kind of rises are going to clump together in which ones are going.
To fall apart. Yes, these would be more difficult to eat with chopsticks, though you know, with enough practice you need almost anything with chopsticks. Yeah, yeah, especially if you got some kind of saucy, wet thing to kind of stick it together. But yes, the grains that separate from one another more easily like this, the long grain rices are more difficult. Meanwhile, shorter grain rices tend to be softer in texture and stickier. They stick to each other
and stick to other things more easily. So you can think of short grain rices like you know ar boreo rice which is commonly used in risotto, or short grain sushi rice which is tender and sticks together nicely to you know, make into sushi rolls or other multiple forms. And this correlates to what you mentioned, Rob that changing ratio of ammelos to amelopectin, longer grain rices tend to have more ammelos and shorter grain rices tend to have less.
Glutenous rice goes even beyond the normal short grain rice. It has especially low ammelose content and high a melopectin, which causes the rice to, once it's cooked, clump together for molding purposes in cooking, and retain a really sticky adhesion between grains while eating. It's also worth noting that sticky rice is used to create a number of secondary food products like Shoushing wine, which is used in a lot of Chinese cooking, is usually made by fermenting a
mash containing glutinous rice. In particular, Japanese sake is an alcoholic beverage that I think is also often made with fermented sticky rice. But I was getting curious about what actually makes the difference. Why do these different ratios of amelos and amlopectin change the stickiness and the texture of rice. Like what's happening at the sort of at the molecular level.
So I was looking all over for a good explanation that I could actually understand of what exactly is happening here, and eventually I found a great article about this by an author named Guy Crosby, who writes about food science for America's Test Kitchen and teaches at the Department of Nutrition at Harvard's chan School of Public Health. And so here's the way Crosby explained it. You got to start
off by understanding what starch is. Starch is a carbohydrate that is found in lots of foods, and it is the natural way that plants store energy, store food energy that they make via the process of photosynthesis. And so this is kind of an interesting connection to like, when you're thinking about the food you eat, think all the way back to like how that energy entered the planet Earth in the form of sunlight and turned into the
food on your plate. So, of course plants make their own food by way of photosynthesis, which means they are forcing a chemical reaction between carbon dioxide in the air and water, and that chemical reaction is powered by the energy from sunlight, and it produces is glucose or sugar carbohydrates as a product that's the food for the plant, and then oxygen as a byproduct. Plants then convert the sugar they produce through photosynthesis into starch, which is a polymer.
It's this huge macromolecule that is composed of smaller individual molecules all linked together in a big chain. And starch is a natural form of high density energy storage. It's a way to squeeze a ton of chemical energy into a very compact space. All of this sugar is packed into one tight, gigantic molecular structure. This starch structure is
known as a granule. So sometimes you can actually look up like microscopic imagery of starch granules and they have a interesting little little like if you look at a cross section of one. Sometimes they'll have these little rings, kind of like the rings of a tree. That's interesting. And when plants make these starch granules, they are storing the glucose in starch in two distinct molecular forms. One
is amylose and one is Amylopectin. These two starches we mentioned earlier ammelos is a linear molecule which is smaller in size, and amylopectin is a larger molecule with a kind of branching out structure, And these amelos and amylopectin pectin molecules are organized into these tight structures called granules. And then inside the granules there are layers with a
different makeup. So there are these like tightly crystallized, highly structured organized layers, and then there are more amorphous, non crystallized layers with more random arrangements of amylose molecules and amylopectin any kind of non regular pattern. So why does that matter, Well, you got to look at what happens when starch granules get cooked in hot water. When the starch granules are in water above a certain temperature, that water starts to pin trait the starch granule, causing it
to swell. So you can imagine water molecules like soaking into something I don't know, like a couch cushion or something and making it like swell up, and that makes it swell up kind of like a balloon in a way. And as these starch granules in hot water get hotter and hotter, they eventually reach a breaking point their maximum volume and viscosity, as Crosby says, and this is called their gelatinization temperature. And eventually what happens is they burst.
They just like leak pieces of starch molecules all out into the water around them. Exactly what temperature this is depends on the type of starch e g. What plant it comes from. And a key factor is the ratio of amylose to amelopectin in each starch granule. So the more amylose there is in the starch, the more the swelling of the granule in the presence of hot water is delayed. So you can kind of think of amylose
as an armor against gelatinization. The more amlos, the higher the gelatinization temperature, and the more the granule fights off the gelatinization process. And then Crosby uses the example of rice to show this process. He writes, quote, long grain rice contains about twenty two to twenty eight percent ammelos by weight, Medium grains contain about sixteen to eighteen percent by weight, while short grain contains less than fifteen percent
to almost no ammelos. Varieties of long grain rice have a gelatinization temperature above one hundred and fifty eight degrees fahrenheit or seventy degrees celsius, while waxy short grain rice gelatinizes at about one hundred and forty four degrees fahrenheit or sixty two degrees celsius. So the temperature in the short grain rice is the temperature for gelatinization is lower, meaning it happens more easily. So the granules of starch in short grain rice with lower ammelose content reach their
gelatinization point and burst at a lower temperature. And when the starch granules burst, they flood the surrounding one with disorganized small chunks of amylos and amylopectant of just little bits of starch, Crosby writes quote, creating an infinite network of entwined molecules that trap water and thicken to a gel on cooling. So this mesh of loose, uncrystallized starch molecules thickens the water and causes the rice grains to
stick together. And you can actually observe a similar principle when you use starch to thicken other foods thicken like a soup or a sauce. If you've ever used a roue based on wheat flour or a corn starch slurry. It's the same principle. Corn starch flour, potato starch and so forth all undergo the same gelatinization process, though at
different temperatures and rates. So the starch granules will swell up and eventually burst in hot water, and this has the effect of increasing the viscosity, meaning the thickness and the stickiness of the water based or sauce. So that is how the lower ratio of ammelos to amelopectin makes the cooked rice sticky.
Ah, fascinating, fascinating. So all that's going on at the at the micro level and at the macro level, you're just enjoying some some sticky rice. Maybe a little sweet, maybe you're a little savory. It kind of depends on the particular dish. I don't think we can properly prepare you for the stickiness just in this audio podcast is something you need to fully to fully appreciate. You need
to try it for yourself. But it's it's generally like when I've had it, oftentimes, not only could you eat it with a with a pair of chopsticks, you could eat it with like one of those little like wooden planks that comes They used to come on the top of ice creams. You could eat it with a popsicle stick, you know.
Mm hmm. Sticky rice is often used for a like molding purposes, so you can wrap it round foods, or you can just use it as sort of like forming little little bits of it or paddles of it in your hand and scoop up foods with it. But there's another thing about the texture of sticky rice, which is that I think it's because of this gelatinization that it has a similar thing going on that like risotto has, which is a creaminess.
Yeah, yeah, I can definitely take on this creamy, gooey kind of texture, has this incredible mouth feel. It can make for an overpoweringly good dessert, but again also works very well in savory and plays a very important role in various cuisines in various traditions, especially I've read in
the culinary traditions of Laos in Laotian cooking. As pointed out by Mike Ives in a Taste of Sticky Rice, Laos's national dish, it can be steamed twice during the course of the day, beginning first thing in the morning. So like traditionally sticky rice is something you make right away, like this is how you start off your day. A third steaming ives rights is said to just make it too chewy to eat at that point, but the author points out that quote a hunk of sticky rice is
a delicious bread like dipping implement. So I looked around at some other sources on this, and yet traditionally in Laotian cuisine, one rolls it up with one's fingers and then dips it into sauces, which is, you know, it is even a little bit different than other uses of sticky rice. You might be more familiar with.
One of the many great world food traditions of make your own utensils and then eat the utensil.
Yeah, yeah, I've been to I think I think I've only been to one Laotian restaurant a couple of times, and I don't remember enjoying the sticky rice like this, And now I want to. I really want to seek it out and have this experience. Anyway, the importance of sticky rice and laos goes well beyond just you know, how you start your day. It factors into Laotian Buddhist rights and traditions will come back a little to a little bit to this in just a few minutes here.
But it also was apparently long sought after by monks because quote as ice rites quote, it takes longer to digest than white rice does. It states hunger for longer periods. So I thought that that was an interesting tidbit. Is
another reason to have it first thing in the morning. Now, whether that actually how much of that is the actual science of the digestion of sticky rice versus other varieties of rice, I don't know, but and I can't help but wonder too if there's some version of like food sticking to your ribs, if there's some sort of like idea of that in Laotian traditions as well. I'm not sure linguistic stickiness and so forth. Anyway, getting into the just sort of the history of rice and the possible
like history of like when did sticky rice emerge? There are various dates you'll come across for some of this. There's so a lot of work has gone into like, well, you know, when do we see this particular rice variety pop up? And what does genetic information tell us the domesticated species or Za sativa or Asian rice evolved starting approximately nine thousand years ago. I've read this according to
Filipino American biologist Michael Pruganin in twenty ten. I've also seen it written that Asian Neolithic farmers are thought to have cultivated rice more than eleven thousand years ago. There may be some wiggle room here again when you get down to exact dates and ideas about when particular plant
varieties emerged or domesticated, et cetera. Now, in the study of rice genetics and in particular sticky rice genetics, Pruganin has several different articles credited to him, and working with Kenneth Olsen for North Carolina State University back in two thousand and two, he set out to explore the origin of sticky rice because ultimately no one knew exactly where it came from. You know, we could look to its importance in these various culinary traditions, but you know, we
didn't have like hard genetic data. Apparently, they pointed out that on one hand, you had a Laotian Buddhist claim that it emerged there eleven thousand years ago. Meanwhile, Chinese folklore suggested that it existed two thousand years ago and so forth. Now I was intrigued by this, you know, mention of the folklore and mythology and so forth. Here I was able to find more on Laotian rice myths, particularly in the book that he cites Rice Legends in
Mainland Southeast Asia by Baron Jay Tierweil. And basically you can find longer versions of this online. But the basically you have this Laotian Buddhist origin story for sticky rice, and it concerns the rice goddess nang Kosap, who is essentially not only a goddess of rice, but is Rice incarnate, who like her body is rice, her identity is rice.
And you know, we see this reflected in the same idea in other traditions, other mythologies, where you have some sort of vital food crop that is personified in a given deity.
Oh well, yeah, I mean I think if the goddess series C E. R e s whose name you see the connection to cereal, the goddess of grain.
Yeah, yeah, you see similarities too to the importance of maize in Mesoamerican traditions. Anyway, the interesting thing about Nan coostop here. The thing I found really interesting is that she has this relationship with humanity, and when the actions of humans upset her or offend her, she'll recede from our world. And of course, when this happens, it results
in famine. So there are at least two vital periods of divine famine in Laotian Buddhist traditions, the second being when an evil king hoards all the rice and then
the rice stops growing elsewhere. And according to the story, after three hundred and twenty years of this particular famine, a wise hermit finally offers to fixed matters, and he does so by sacrificing the goddess pulls her into pieces, and each of these pieces would become one of the four main varieties of rice that are of special value in Laotian cuisine, black rice, white rice, anim rice, and
sticky rice. And it said that she does not resist this, she just holds her breath and dies as she's divided into these pieces. But on top of this, there's this added level of prophecy. When Maitreya, the Bodhisattva of the future, is born on this world, quote all rice varieties will reunify to become the original Rice.
Whoa Well, on one hand, I was going to say that is an apocalyptic prophecy of the future that I can get behind. But then the more I think about it, I'm like, wait, but I like all the different varieties of Rice.
But you haven't tried the original Rice.
Right, Well, that's true. Maybe maybe it would be as good as all of them put together.
There there are you know, I don't didn't have time to get into it so much for this episode, but this particular source, this book Rice Legends in mainland Southeast Asia. It you know, it also gets into these various other ideas and myths concerning Rice about how Rice used to be bigger. I think in some cases, like they're talking about back when rice was the size of like coconuts or something, you know, so.
You know their grain.
Wow, yeah, I guess so. And then there are various stories about, well, it's not as big as it used to be because it was cursed by a widow. And in some cases, like Rice in general is lost and
then found again. So it looks like there's a there's a lot of fascinating twist and turns in the sort of mythic history of rice, and you wonder about like the various disasters that that it speaks to you times when rice crops were lost, or people moved from one region to another and had to sort of refined or adapt their method of growing rice and so forth.
That's an interesting ideology.
So anyway back to the actual origins of rice as far as DNA evidence reveals. So back in two thousand and one, Programon's team found that sticky rice's genetic mutation maps to a single mutation on the genetic tree, suggesting that it occurred only once. They looked at the geographic data for the rice DNA sequences and found that Southeast Asia was in fact the likely location of its emergence.
So the picture we see of rice cultivation suddenly here is rice cultivation suddenly generates something new and exciting, and it's something where people latch onto it. There they're like, Okay, well this is different. I think we can do different things with this. And in this particular case, we're talking about chewiness. We're also talking about you know, stickiness, but I guess once it's in your mouth, it's not about
being sticky. It's about being chewy. And also in the Laotian example about like rolling up the rice and dipping it, it also shows that like the stickier the rice and or chewier the rice, it opens up new ways of using it physically in your food, Like it's no longer has to be in the bowl. Well, now we can dip it in the bowl. Like you say, it becomes the utensil.
Yeah, you can almost treat it more like like a dough or something, except it's a dough that like is already cooked and ready to eat. It's as moldible as a dough, but it's already ready to go. Yeah.
And Japanese moch is just another example of this as well, Like that chewiness, the things you can do with it. So why do we like chewy foods? Why would withou this chewy aspect of this rice, The sticky aspect of this rice, you know, cause it to be picked up and embraced and then cultivated. Well, I found an interesting article about this that touches on some of the you know the differences between particularly between Eastern and Western culinary traditions.
And this was a bone Appetite article titled everyone Loves Crispy and crunchy, But what about chewy? This is from twenty nineteen by author Elise in Nominee. My apologies if I've got the pronunciation on that last name wrong, but it's a wonderful article, and she points out that in the modern West, chewy may sometimes be associated with something that's underdone or overdone, you know, the results of poor cooking.
You know, why is this steak so chewy? Or why is this other you know, I can't think of any other specific examples off the top of my head, but this is chewy? Please take it back?
Yeah, I mean traditionally, like the way meats are priced in American supermarkets is there's a direct correlation with tender, Like the dollar amount per pound of meat directly correlates to how naturally tender is the meat. And so your quote, cheap cuts of meat are the ones that are going to be really tough unless you subject them to long, slow cooking processes.
Yeah. But according to the author, here in Eastern Cuisines, there's this richer history of chewy foods, and one of her key arguments for the enjoyment of chewy foods is that it kind of prolongs the tasting experience, which is interesting because on a basic level, you're working over the texture and flavor in your mouth much longer. She argues that across East and Southeast Asian cuisines, chewiness quote isn't just a common texture, but a powerful tool deployed to
make food taste better. So this idea of stickiness or chewiness is kind of a flavor enhancer of sorts.
That's interesting.
Something this reminds me of the discussion is also even in case you encounter these I think they're called talk rice cakes. They are these like chewy little rice cakes that you get in various Korean stews. Have you had these before, Joe.
Yes, I think so. They're made with well, I don't know exactly how they're made. I assume they're made with either rice flour or something or like mashed up grains of rice, but they are. They form like a solid white puck sort of, and yeah, they've got a really nice bouncy, chewy, springy texture, kind of like rice noodles, but very thick.
Yeah, and I can see where like having those nice chewy bits in this flavorful stew, you know, it kind of forces you to to sort of experience the flavors in that stew in a different way. So yeah, this really made me rethink a lot of the ways that I'm encountering chewy bits and various foods. Now, the usefulness of stickiness and sticky rice also goes well beyond culinary uses.
It also factors into sticky rice mortar, an ancient, apparently Chinese development that dates back a good fifteen hundred years. We'll get into some of the discussions about how far back this might go, but basically it's a mixture of slacked lime with sticky rice soup. I was reading about this in in a paper from twenty nineteen by Lee and Zang published in the Journal of Archaeological Method and Theory.
This was this is an interesting when the authors looked at three hundred and seventy eight ancient mortar samples from throughout China across one hundred and fifty nine ancient buildings in archaeological relics. Two hundred and nineteen mortar samples from ninety six buildings contained organic components. One hundred and twelve samples contained starch, eighty seven oil, fifty nine protein, fourteen sugar,
and five blood. Who now on the blood point. I'm not going to go too deep into this here, but I think there might be a temptation for us to instantly think about, you know, some of like sacrificial aspect, and you do see sacrificial rites associated with various building traditions throughout the world, you know, foundation sacrifices and so forth. But also you see a lot of these sorts of organic ingredients used in various things like dyes and paints,
et cetera. So you know, one thinks too like the use of organic bits from egg and paints that were used to create various works of art. But the authors here point out that the of course, the line portion of mortar goes way back to somewhere between seven and
twelve thousand BCE and Palestine and Turkey. Various inorganic additives were used throughout the history of mortar, such as volcanic ash, which was often added by the Greeks, but organic additives were used as well, including just about anything you could think of animal here, plant seeds, plant fibers, egg wides, egg yolk, animal glue, fish oil, whale oil, all sorts
of stuff. Now, Chinese use of lime mortar goes back a good five thousand years, they say, but there's evidence of different additives being used at different points in different places. Sticky rice in particular pops up in tombs and pagodas dated to the Southern and Northern dynasties. This would have been between the years four twenty and five to eighty nine. The starch content of their samples are directly linked to the extremely common practice of using sticky rice mortar. Some
of the samples included city walls. They also point out that while the Southern and Northern dynasties are generally considered the earliest possible time for sticky rice mortar to have been used in China, they claim to have found one starch sample from the Eastern Han dynasty that would have been between the years twenty five and two twenty, which, if accurate, would push that estimate back.
All right, So why would you be adding food substances like sticky rice or any of these other things to the mortar you were using to build buildings.
I mean, basically it comes down to, like trying to make a better mortar. Things you can add to increase the bond strength in the mortar, And that seems to
be the case here. A twenty ten paper published in the American Chemical Society monthly journal Accounts of Chemical Research by Yang at All looked into the legendary strength of sticky rice mortar, because all these stories about how strong it was and how strong it still is, how well it holds up, they're like anecdotes about like modern bulldozers
not being able to knock it down. And they found that, you know, first of all, it's the emelopectin that's the key ingredient in the sticky rice soup that helps strengthen the mortar. It acts as an inhibitor, controlling the growth of the calcium carbonate crystals, producing a compact microstructure. So this results in improved mechanical strength, makes it less permeable
to water and more resistant to weather related stresses. They also point out that it's it's key to recreate ate this sort of mortar for restoration work on ancient buildings. I hadn't thought about this, but they make the case that because modern mortar, of course, it's come a long ways, and it can actually prove too strong and it can damage older, softer bricks, which, of course I'm not sure we're necessarily talking about situations where we're using mud bricks.
But it makes me think back to our discussion of mud bricks on the show previously.
Oh interesting, but in this case, if they found it's the amelopectin which gives the mortar the desirable quality. Here, So this is why sticky rice in particular would be useful because it's got the highest ratio of amelopectin the lowest ratio of ammelose.
Yes and therefore apparently resulted in just a superior mortar for a very long time. And you know that again frequently used in things like like walls and tombs and so forth, city walls in particular, so defensive structures.
The sticky rice is not just delicious, it's not just and muldable. It keeps us safe.
Yeah, So it's a it's fascinating to try and sort of imagine these developments, you know, like how much of it is just let's try anything. Let's let's just experiment with adding different organic and inorganic ingredients to mortar to see what we can get, but also that kind of experiential level of like, well, look at what happens with this particular type of rice. We know how sticky it can get. We know how chewy it can get. Let's experiment with just with adding this to the mortar. It
makes sense and then it pays off gorgeous. Yeah, because that what you want your buildings to stick together? Right?
All right, Well, maybe that is going to do it for part one of the series, but we will be back to talk about stickiness and sticky things more in part two.
That's right. We already have some avenues mapped out for us here, but it's possible there's something we haven't thought of. So if there's a particular sticky topic or sticky stickiness related topic'd like for us discuss to discuss on this series,
just write in. We'd love to hear from you. A reminder that Stuff to Blow Your Mind is primarily a science podcast with regular core episodes on Tuesdays and Thursdays, but on Mondays we do a little listener mail, on Wednesdays we do a short form artifact or monster fact, and on Fridays we set aside most serious concerns to just talk about a weird film on Weird House Cinema.
Huge thanks as always to our excellent audio producer JJ Posway. If you would like to get in touch with us with feedback on this episode or any other, to suggest topic for the future, or just to say hello. You can email us at contact Stuff to Blow Your Mind dot com.
Stuff to Blow Your Mind is production of iHeartRadio. For more podcasts from my heart Radio, visit the iHeartRadio app, Apple Podcasts, or wherever you listening to your favorite shows.