Stuff You Should Know - Short Stuff: Yakhchāls - Ancient Fridges

Short Stuff: Yakhchāls - Ancient Fridges

Feb 12, 2025 - 11m 16s

If you lived in ancient Persia, you could do a lot worse in trying to cool things down than by building a yakhchāl. Today we break down how the early fridges worked.

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If you lived in ancient Persia, you could do a lot worse in trying to cool things down than by building a yakhchāl. Today we break down how the early fridges worked.

See omnystudio.com/listener for privacy information.

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Introduction to Yakhchāls

In this episode, the hosts Josh and Chuck dive into the fascinating world of yakhchāls, ancient refrigeration systems used in Persia. They introduce the concept by contrasting the modern conveniences of refrigeration with the ingeniously designed structures that enabled people to preserve ice in extreme conditions in 400 BC. Yakhchāls utilized innovative architectural features to exploit environmental factors for cooling.

Construction and Functionality of Yakhchāls

The hosts break down the construction of yakhchāls, highlighting the unique materials used such as goat hair, egg whites, and clay, which provided remarkable insulation capabilities. They discuss the design elements that contributed to the refrigeration process, including high walls that shielded from direct sunlight and allowed for effective ice preservation over the summer months, enabling the storage of ice and food.

Culinary Uses of Ice

Further into the discussion, Josh and Chuck explore how ancient Persians made use of ice from yakhchāls, from cooling food to creating delicious traditional desserts like Faluda. They paint a picture of the cultural significance of ice in gastronomy and how this ancient practice shaped communal and private culinary experiences.

The Decline of Yakhchāls and Modern Relevance

In the closing sections, the conversation shifts to the decline of yakhchāls with the advent of modern refrigeration technology. The hosts reflect on the health concerns tied to the traditional ice production method, highlighting how dust contamination led to decreased use. They conclude by discussing efforts in contemporary times to preserve yakhchāls as cultural heritage sites and the valuable lessons they can teach about resource-efficient cooling.

Transcription

Los Angeles 2021, a friendly neighbor appears out of nowhere and promises to make all my dreams come true.

Let's not forget that David Bloom was a professional con artist, so you didn't stand a chance.

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Hey and welcome to the short stuff, I'm Josh and there's Chuck Jerry sitting in free Dave and so this is short stuff.

How do you say this again?

Edition.

Yeah, I'm going to say it's pronounced spelled Y-A-K-H, you know, as most words are.

C-H-A-A-L, I'm going to say, Yacht calls.

I'm going with the straight-ahead Yacht calls.

All right.

Okay.

So you say it your way throughout, I'll say it my way, and I'm sure I'll inevitably unconsciously start saying it your way.

Well, see.

But what we're talking about is the promise from our refrigeration episode, a little bit more on these ancient, basically ancient refrigerators or cooling systems that were found across ancient Persia, at least as old as 400 BC, this is modern-day Iran.

And these are places where, believe it or not, the climate enables freezing of ice when you would not think you should be able to freeze ice.

Yeah, it's pretty amazing.

And apparently still today in Iran, Afghanistan and Tajikistan, to Geekstant, yeah, they said it right the first time.

They call the refrigerators Yacht Chals, which is how I would say it if I were in Iran, but that's the name for the fridge, which means that at some point someone in Iran has gone into a store and said, you got a smeg Yacht Chal?

Yeah, exactly.

And these have been the fascination of like, everyone from engineers to historians to physicists over the years because they're just, So kind of confusing and how they actually work and I'm still not entirely sure how it works.

It seems to be a little magic involved.

One thing I know goes a long way toward keeping this ice and we got to say some of the sizes is mine from the mountains and brought down and preserved.

Some is made on site.

We'll get to that.

But one big factor is the insulation of the structure itself, which is made from a mortar called Sirouge, sand clay, egg whites, lime, goat hair, and ash, quite a mixture.

Some of these were several meters thick, some of these yak chiles were, but there was a study, we got some of this information from the engineering firm Max Fordham, and they We did an analysis from 2018 of Yacht Chiles and just how effective they might have been, and they found that the walls of a Yacht Chile had the same insulative properties as a wall of concrete, three inches thick, surrounded by a one-foot thick wrapping of Styrofoam insulation.

That's how effective these things were.

Sandclay, egg whites, lime, and goat hair and ash.

I was going to say like the secret of egg whites, but...

Who knows?

You took goat hair in there and yeah.

Who knows with the secret?

I think the secret is the whole thing together, the whole se-r-ooge mixture.

Yeah, probably so.

So I mentioned that sometimes the ice was brought in from the mountains and kept there throughout the year, but usually what would happen is, is they would make ice, they would bring in water, they would divert water from an aqueduct through these underground water channels called canots.

And they would channel them to the north side of this wall.

It's another thing we haven't mentioned yet is they have these very, very high walls that act as shade for these channels to keep the wind off of it because stuff isn't going to freeze as fast if it's moving.

So to keep the water still and to keep it cooler away from that sun.

Yeah, and so the channel has a little diversion into a trench or a pit or like a very shallow like rectangular pond usually, and they'll divert water in there to fill it up, and then they let it freeze overnight.

Over the course of a few nights, it'll continue to freeze and freeze and freeze in layers.

And what they're taking advantage of, you know, like when it snows, and then the temperatures heat up in all the snow melts but there's a little pile of snow like in a shaded corner of your yard that never gets direct sunlight and it just takes forever to melt.

That was right.

They're giving you advantage of the same thing.

They're building that big old wall to keep it shaded and just let this ice grow and grow and grow and then once it reaches I think 50 centimeters which is like about a half a meter thick, then they'll cut it into blocks and they put it in the yacht shell and they store it through summer.

Like this stuff will stay frozen for an entire summer.

So in that sense these yacht shells are built to store cold throughout the course of a year.

Even when the summer comes around, still cold.

Yeah.

Another way that helps us out is that dome shape.

It's not domed because they like domes, even though domes are nice.

It's conical because that optimizes what's called the solar chimney effect is that's when you create a convection current letting that heat go up and out through these openings at the top and bringing in that cool air from the bottom.

They also have wind catchers that they call beggiers and they actually take wind and direct it downward into the yatchal dome and so the the area that hits it is cooled by the ice and the air that's not cooled by it or cooled enough like you said that chimney effect takes it up along the curved sides toward the hole in the top and it says see you later don't come back that's right and that feels like a good time for a break and we'll come Don't miss real-life amigos, Wilmer Valderama, and Freddie Redrigas in their new podcast, Dosa Amigos.

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Alright, so they're making ice, they're preserving ice.

What are they doing with all of this ice?

One of the things they're doing is using it as a refrigerator, you know, they'll store food in there that they don't want to go bad and just using it as a cold house.

They will also just use the ice to eat in a treat.

They have something called Faluda over there, it's a Persian traditional dessert.

has thin vermicelli noodles made from cornstarch and then you mix that up with a little semi-frozen syrup of sugar and rose water and then serve it up with the lime juice and maybe some ground pistachios and it's like a little Persian icy.

That has to be better than it sounds, don't you think?

Oh I think it sounds great.

I think the pistachios are where to throw me off.

Oh yeah.

You don't like pistachios or?

I do like pistachios.

They don't seem to go with the rest of the ingredients.

But like I said, I'm sure it's delicious.

I mean, it's a traditional Persian dessert.

It's got staying power.

So, yeah.

Who am I to question Faluda?

Exactly, how about it's delicious.

One of the cool things about this is that Yacht Charles, I mean, there's some still around.

I think there's one in Kerman Iran that's about the size of a five-story building.

So you would think, of course, obviously, this was reserved for royalty.

You would be dead wrong, because not only were Yak Chels open and available to the public, there are some that people just built for their houses that were of private use as well.

Yeah, for sure.

They would make those delicious feluda.

They would make sherbet and preserve them.

And then that's fruit and ice.

and they would put them on a donkey and go sell them at market and stuff like that.

They would sell ice directly from those places sometimes.

And one of the things they're also taking advantage of is the greenhouse effect.

The earth is going to stay fairly warm at night because of the greenhouse effect, trapping those gases in the atmosphere.

But if it's low humidity and if it's a really clear night, that effect is going to be weaker and that heat can dissipate and disappear more readily and so that's when they discovered like hey we can make these little thin layers of ice and kind of build you know day by day night by night on these clear low humidity nights eventually to get you know some pretty significant ice.

And once they figure that out someone said go get the donkey.

Exactly.

It's time to sell some sherbet.

And harvest some goat hair.

One other thing I saw in that max Fordham analysis.

They figured out that they could make about what would be equivalent to three million ice cubes a season.

Wow.

Yeah, which is a lot, but they were like, you'd think it'd be more.

And I was like, it seems pretty good to me, especially in 400 BC, you know?

Yeah, depends on how big those cubes were.

Were they big fancy cocktail cubes?

That's a lot more ice than an ice nugget.

That's right.

You're absolutely right.

I expect that they're probably all donkey head size.

So three million donkey head size ice cubes.

That's big.

Think about the poor donkey that had to cart those around.

I know, no fun.

You got anything else?

Yeah, I mean these went away obviously because of modern refrigeration came on the scene and also one thing that was happening was they were making this ice kind of out in the open and a lot of it would get contaminated with dust and it wasn't like the healthiest ice in the world and so that combined with modern refrigeration coming along they're like maybe we should just not have these much anymore but like you mentioned there is one still around at least in Kerman and there are groups there that are trying to preserve this way of life and at least keep it you know not like a chief refrigerating method but like hey we can't lose our culture and so let's work to take some of these old ones and restore them at least even if only for like museum and touring purposes.

For sure.

But also, there's a lot to learn from them, especially when we're trying to advance like passive cooling and other things that require less energy to cool things down, yak-challs or something to turn to and say, how do we do this and someone says, go get the goat here.

That's right.

We'll get some egg whites to do.

No one likes this.

All right.

What do we do with all these yolks?

Yeah.

Well, I think that's it for short stuff, right Chuck?

I think so.

Well, that means short stuff is that.

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