Saké has long been considered the national drink of Japan. But as its popularity spreads around the world, the secrets behind its ancient traditions have come to light.

1. Saké has more in common with beer than wine.

Though English-speaking countries often refer to saké as "rice wine," that's a misnomer. Rice wine is made from the fermentation of rice, while Western wines are made of the fermentation of grapes. Saké is made from rice, but through a brewing process that converts starch to alcohol, similar to the way that beer is made.

2. Brewing saké is an arduous process.

Saké rice is first stripped of protein and oils in "polishing," then washed of its debris and air-dried. After being steamed, Koji is kneaded into the rice by hand or by machines. Koji is a mold that will help convert rice starch to sugar, which will turn into alcohol during the two-step fermentation process (Shubo and Moromi).

This second fermentation stage lasts 25 to 30 days, depending on the type of saké being made. During this time the brewers will keep close watch on the batch day and night, adjusting temperature and ingredients as needed. Finally, in the Jo-So stage, the rice mash is pressed. The resulting saké is bottled.

3. Brewing saké can be a communal process.

In the investigatory documentary The Birth of Saké, which is currently playing at Tribeca Film Festival, filmmaker Erik Shirai takes viewers behind the scenes of the 144-year-old Yoshida Brewery in Northern Japan, which still uses manpower over mechanization for several of the steps above. To accomplish this, their workers spend half the year (October through mid-April) living onsite (and away from family and friends) to oversee the saké's creation around the clock.

4. Saké breweries have brewmasters.

Their official title in Japan is "Tōji." A brewery's Tōji is not only responsible for the taste of the brew, but also for keeping his or her team in harmony during the long winter months of work and communal living. The Tōji is a parental figure to his or her team, and will eventually mentor the next potential Tōji in an apprenticeship that can take decades.

Traditionally, the skills of saké-making are passed down through oral tradition and hands-on-training instead of through schools or books.

5. More polishing means higher-grade saké.

Saké designations like Futsu, Honjozo, Tokubetsu, Ginjo, and Daiginjo are determined by how much of the rice grain was polished away in processing. The lowest grade has 30 percent or less of its grain polished off, while the highest grade (Daiginj) has 50 percent polished away. If any of the above is paired with "Junmai" (which translates to "pure rice"), it means that bottle of sake had no distilled alcohol added to its mash. It's purely rice-made alcohol.

6. Saké has a higher alcohol content than either beer or wine.

The ABV (alcohol by volume) of beer is typically between 3 and 9 percent, while wine is between 9 and 16 percent. Saké can be upwards of 18 to 20 percent. Hard liquors have the highest ABV, with 24 to 40 percent.

7. Yeast is a key flavor component.

In Birth of Saké, Shirai shares that "Yeast plays a critical role in saké's quality. Because each strain of yeast yields its own distinct characteristics of aroma and taste, brewers must test which yeast is best for their saké." This is a delicate taste test overseen not just by the Tōji, but also by brewery executives.

8. It's the oldest known spirit in the world.

Some say the origins of saké date back to 4800 BC China. It wasn't until 300 BC that saké came to Japan with wet rice cultivation. But since then, Japan's development of the drink has made it synonymous with this nation.

By the 1300s, breweries were built that allowed for mass production of saké. The industrial revolution brought machines that did the work once done by villagers' hands. And in 1904, Japan created a research institute to study the best means of fermenting rice for saké.

9. Now a male-dominated industry, saké-making was once considered women's work.

The origin of the word "Tōji" bears a deep similarity for a Japanese word that translates to "an independent woman." Other clues to the feminine influence on the drink's history include how housewives were once called the "toji of the house," and how a woman was listed as the toji for the Imperial court. Men seemed to take over saké production in the late 16th and early 17th centuries.

10. Spit used to be a key ingredient.

Today Koji fungus is used to ferment the rice. But long ago villagers would gather together to chew on the polished rice and then spit its mashed remains into a communal tub. The enzymes of their saliva aided fermentation. Of the various tweaks saké brewing has seen over the years, this is probably the tradition least missed by even its most hardcore connoisseurs.

11. Saké can be served cold, room temperature, or hot.

Where you'd never dream of drinking a warm beer on purpose, heated saké has been enjoyed in Japan since the Heian era (794 to 1185). Temperature influences the taste; the warmer it is, the drier its flavor.

Pairing suggestions for hot saké (called joukan) are dishes with lots of oil or fat. Warm saké (nurukan) pairs well with cold foods, like sushi. And chilled saké (reishu) is recommended for lightly sweet or sour foods. But another major factor in choosing a temperature is the weather and the season. Few people prefer to drink hot saké on a sunny summer day.

12. It's kind of rude to pour your own glass of saké.

Some say serving yourself suggests you don't trust your host to take care of you. But it's more about saké-drinking's focus on friendship. Loved ones use saké to toast weddings, the New Year, and other celebrations. So pouring for a friend—and letting them do the same for you—is meant to be an act of bonding.

13. Saké serving has changed dramatically.

Traditionally saké was served one of two ways: the first was in a choko, a small ceramic cup accompanied by a ceramic flask called a tokkuri. The other was a small wooden cup called a masu, which would either have a choko in it, or would sit on a saucer. Either way, the drink might be poured so that it spilled over the cup's rim, a sign of the host's generosity.

Nowadays any kind of glassware will do, especially as saké finds its way across the world and into cocktails. But spilling saké is a custom that has not caught on abroad.

14. Saké's popularity has withered in Japan.

Reflecting a growing interest in western culture since the 1970s, Japanese drinkers have taken to beer, wine, whiskey, and shōchū, which has had a drastic impact on the saké industry. The Guardian once estimated that the Japanese public drinks about one-third of the saké now that they did 30 years ago.

In the early 1900s, Japan boasted 4,600 saké breweries. Today, only around 1,000 remain. Another reason for this decline is a 20-year-old tax agency's decision that denied breweries renewed licenses when their Tōjis retired without a successor.

15. But saké's popularity is blossoming abroad.

With breweries boarding up and Japanese drinkers turning to other boozy beverages, saké's survival may depend on its appeal overseas. The demand for saké in the U.S., Taiwan, Hong Kong, and China has been on the rise. Not only has exporting to these nations been a major help to saké breweries, but some believe that America's growing interest in saké could spur a renewed interest in it back home.

Yasutaka Daimon, the sixth-generation head of his family's brewery, told The Guardian, "The Japanese are very concerned about what foreigners think of their country, so if we have more success in the U.S. market, then Japanese consumers may give it another try."