The preschool, along with Casscar Creative Art Studio, created an eight-metre balloon sculpture that was launched at Chinaman’s Hollow cricket ground.

The balloon – made of plastic bags bonded with packing tape – was designed to inflate with air, and then lift with the warmth of the sun.

It was tied to stakes as a precaution, but it unexpectedly broke its tethers and floated away at about 8am.

The project – called Museo Aero Solar – was the first of its kind to be launched in Australia.

Contributing artist Andrew Styan was inspired by the Aerocene solar sculptures of Tomas Saraceno, seen at the 2015 UN Climate Change Conference.

Mr Styan he believed it would be “touch-and-go” whether the balloon would fly, let alone take off.

The balloon was sighted at Morpeth heading north-north-east just after 9am, so Mr Styan made his way to Clarence Town to ask around, but to no avail.

Kurri Kurri Preschool project officer Janet Murray said it was a great example of the power of the sun.

“There was a bit of cloud cover when it was inflating, but once it got the full sun on it, it really quickly lifted itself,” she said.

“No-one was anticipating that.

“Our expectations for success should have been higher.”

About 30 children from the preschool were involved in the art-and-science project over the past six months.

Families provided thousands of used plastic bags, which were opened out and decorated by the preschool children and Casscar students, then arranged into a sculpture under the direction of Casscar principal Sandii Walker and Mr Styan.

Ms Murray said the project has posed many questions for all involved, particularly around daily plastic consumption and careless use of resources.

“These bags are used for about nine minutes then discarded, yet are products of an intensive industrial process,” she said.

Despite the surprising mishap, Ms Murray said it was a great project for the children to be part of.

“The kids who were there will never forget it,” she said.

Mr Styan agreed: “It’s been really positive and engaging, creating conversations about not just recycling, but also the environment and geography,” he said.

The organisers were liaising with police and aviation safety authorities about the balloon’s whereabouts.

They were keeping their fingers crossed that the balloon would be found as the sun goes down on Tuesday.

“The project was designed to raise awareness of the sheer numbers of plastic bags that we use,” Ms Murray said.

“The last thing we wanted to do is pollute the environment.”

If it is recovered, the preschool will be looking for another school or community to join and expand the balloon for its next flight.