But after 30 days, it'll become this.

High-quality bamboo salt costs almost $100

for an 8.5-ounce jar,

making it the most expensive salt in the world.

So, what is bamboo salt used for?

And why is it so expensive?

For hundreds of years,

Koreans have used bamboo salt for cooking

and as a form of traditional medicine.

It's made by placing sea salt inside of bamboo

and roasting it at a high temperature.

The goal is to infuse the salt with minerals from the bamboo

and to remove any impurities.

But the premium compared to other types of salt is steep.

Nine-times-roasted bamboo salt,

sometimes referred to as "purple bamboo salt,"

can cost over 10 times the price of pink Himalayan salt.

Most of that cost comes from the labor-intensive process.

Every single step is done by hand.

Narrator: The process starts by cutting 3-year-old bamboo

into uniform trunks,

leaving one side closed as a container for the salt.

Sea salt from the west coast of Korea

is densely packed by hand into the bamboo.

Workers load filled bamboo onto a cart

and push it into a kiln.

Traditionally, only pine logs are used.

This process takes around 12 to 14 hours.

Baking everything at over 800 degrees Celsius

burns away the bamboo, leaving a column of salt.

But the process has only just begun.

Narrator: The ninth and final roast is the hottest,

at over 1,000 degrees Celsius.

It's fired in a special kiln and operated by an expert.

Shin Tae-joong has been making bamboo salt

for over 20 years.

That experience is extremely important,

because any error at this stage

could result in wasting a month of work.

At this temperature, the salt and bamboo completely melt

and drain into a mold.

After a few days of cooling,

a blackened rocklike structure remains.

This is nine-times-roasted bamboo salt.

Workers carefully break this down by hand,

trying not to waste any material.

After a month of work,

it's ready to be packaged and sold.

Narrator: The final price varies

depending on where you buy it and what form it's in.

But nine-times-roasted bamboo salt doesn't come cheap.

Narrator: The health benefits of food

have always played an important role in Korean culture.

For centuries, bamboo salt baked two to three times

has been used in traditional Korean medicine.

But in the 20th century,

the nine-times-roasting process was developed.

Manufacturers say this process has the lowest toxicity

and highest mineral content.

Today, it's used for cooking, toothpaste, soap,

and various remedies.

Narrator: Proponents of bamboo salt say that it can help

with everything from digestion to oral health,

skin care, and inflammation

and that it even has anticancer effects.

The proposed medical benefits have likely helped it

maintain its high price.

But there hasn't been enough scientific study

to fully back up all of these claims.

Studies have shown that bamboo salt contains higher levels

of iron, potassium, and calcium

compared to regular sea salt

and that it could improve your immune system.

But these beneficial minerals constitute

only a small percentage --

the majority of bamboo salt is sodium chloride.

Even with lower toxicity,

it's unclear how potent the health benefits are.

In 2016, the WHO wrote in a report

that "the composition of specialty salts

poses no toxicological risks

but does not offer any relevant

nutritional benefits either."

The full benefits of bamboo salt compared to sea salt

have yet to be extensively researched.

But despite that, bamboo salt continues to be popular.

Insanga, a popular bamboo-salt maker,

earned around $24 million in sales in 2017.

And the traditional labor-intense process

isn't likely to change anytime soon.