The sizes, shapes and thickness decide the sound of explosion, a young man told the audience as he raised high a conical hat-shaped cracker that he had just finished making.
When he said any child can give the crackers a try, about 10 boys and girls jumped in, rolling up their sleeves.
"I never made this before. This game is a lot of fun," said Le Quoc Minh, a seventh grader from the Nghia Tan Secondary School in Cau Giay District.
"I made one small one and one slightly bigger. They did not make such a big bang, but I would love to try again."
The clay crackers were demonstrated by artisans from Hai Phong City at a spring festival hosted last weekend by the museum in Ha Noi.
The artisans from Hai Phong were joined by their counterparts from Ha Tinh and Hoa Binh provinces, who presented several folk games and art performances.
Several groups of girls, women and even little children enjoyed a bamboo pole dance introduced by people of the Thai ethnic minority community. Among the audience cheering and applauding the dancers were several foreign visitors. In other corner, many young people and even children kept onlookers entertained as they tried their best to walk on stilts.
Others tried their hand at climbing tall bamboo poles, catching loaches in big jars, a game that involved rolling pomelos (akin to bowling) through a small "goal post," sack jumping and several other of 25 games brought to the festival.
"Many localities have begun to revive and promote their folk games at spring festivals that are being held nationwide, said Nguyen Van Huy of the National Council for Cultural Heritage.
A former director of the museum, Huy welcomed the development saying: Folk games reflect the nation's culture, they enable us to understand more about friendship, love for family and the homeland, enhance community spirit and connect the neighbourhood."
The interest and enjoyment shown at several spring festivals by both Vietnamese and foreign visitors, in particular the youth, show that folk games can still be a big draw, he said. "If we go in the right direction, these games will not be lost, and can actually flourish."
The ongoing Tran Temple festivals in the northern provinces of Nam Dinh and Thai Binh have helped revitalise folk games like kylin and dragon dances, human chess, wrestling and several forms of martial arts.
Viet Nam celebrates around 8,000 festivals each year. Apart from the main activity – rituals – folk games are still considered the soul of most festivals, and as such, play a significant role in developing the nation's culture, experts say.
"Folk games are not just a form of healthy entertainment and good physical exercise. They also stimulate the players' intelligence," culture researcher Giang Quan told the Ha Noi Moi (New Ha Noi) newspaper recently. "Many games are artistic and aesthetic, and highlight the admirable skills of players."
Another culture researcher, professor Ngo Duc Thinh, told Viet Nam News that festivals are a great environment for the games that go beyond mere entertainment.
"Folk games have a religious and spiritual base. Hence they are not simply games. They also help improve physical fitness and provide moral education," he said.
Thinh gave the example of a swing competition where male-female pairor martial arts performance represents the combination Yin and Yang, or martial arts performance in which winners have the coveted honour of praying in front of the local God. The belief is that such an honour will bring them health, happiness and prosperity during the Lunar New Year, he said.
However, Thinh also said there is some worry that folk games were better conserved in mountainous and remotes areas, not in urban areas where imported toys dominate the market.
"In recent years, both culture managers and researchers have paid greater attention to conserving traditional games in an effort to keep children off these harmful toys," Thinh said.
"However, it's easier said than done. Results in terms of both quality and quantity remain limited because of inadequate organisation."
Prof. Thinh said Viet Nam, South Korea and some other Asian nations are jointly compiling documents to have some common traditional games recognised as a world heritage.
While this is good, it is much more important to ensure that folk games are brought into full play in the daily life of local communities, he said.
He said: "Any folk game, especially for children, will only fulfill its potential if it's played all year around, and not just during festivals."