In the latest round of Boston versus potholes, the city is bringing in the big guns: a Silly Putty-like material encased in portable plastic bags invented by college students. Shape-shifting goo that hardens instantly under pressure.

The innovative, eco-friendly pothole filling materials that the city will test over the next six months are more expensive than regular asphalt, but could help public works staff repair the craters more quickly than ever before.

“There’s a lot of work in materials science that can help us figure out how to make roads smoother for residents,” said Chris Osgood, cochairman of the Mayor’s Office of New Urban Mechanics, which recently introduced a pothole-
spotting smartphone app.

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It’s a perpetual problem for public works officials: What to do with potholes that are discovered on nights or weekends, when asphalt plants are closed and there are no options to permanently fill them?

Elmo Baldassari, Boston’s deputy commissioner of public works, said officials are hoping two of the test products demonstrated during a press conference Thursday could help his staff permanently repair potholes on the fly, rather than putting in temporary fixes that must be replaced weeks or months later.

“We’re not afraid to look at technology that’s cost-effective,” Baldassari said. On Bowdoin Street, a Dorchester street pockmarked with yawning cavities, city officials and representatives from three pavement material companies showed how the quick-fix products could fill a trio of the street’s worst offenders.

The fillers do not have as many ill-effects on the environment and can be carried in bags or buckets in the back of a truck, unlike asphalt.

If two of the asphalt alternatives work as promised, said Baldassari, “we won’t have to come back here in six or seven months, chasing our tails. We could do it once and be done.”

Travis Crosby, US national sales manager for Aquaphalt, demonstrated his company’s product, pouring black sticky material from a bucket into a hole, then raking it over and tamping it down with a heavy metal tool.

“That’s it,” Crosby declared. “She’s done.”

The appeal, Crosby said, is that the material stays pliable, and conforms to the pothole.

Representatives for Unique Paving Materials said their product works in a similar fashion: While the thick, black substance hardens on the surface, layers beneath remain elastic, which means that even if further chinks appear in the surrounding asphalt, the patch will hold strong.

“You’ve got cars coming through here; you’ve got freeze-thaw cycles,” said Michael Wohlfahrt, the company’s account executive. “We want the patch to be able to move with the pavement.”

The third company in the demonstration took a more unusual approach: Their product, called Hole Patch, consists of a Silly Putty-like material encased in hardy plastic bags and is meant to be temporary.

The company’s founders, recent graduates of Case Western Reserve University in Cleveland, believe the pliable bags can serve as a fix for a few hours or days, preventing damage to passing vehicles before crews can make a permanent repair.

The sack of putty is contains a thick liquid, but under pressure, such as the weight of a passing car, it becomes solid. After the pressure subsides, the product becomes putty once again, which means it could be reused in different potholes.

Nicholas Barron, one of the cofounders, demonstrated: He tossed one of the sacks in a pothole. Then he tossed another one.

In all of seven seconds, the job was done.

“It’s that easy, just throw and go,” Barron said.

The bags would not replace road crew work, said John Guilfoil, a spokesman for Mayor Thomas M. Menino’s office .

Instead, he said, officials envision that the bags could be kept in the trunks of police cars or other city vehicles. Passing a pothole, city workers could plop a few of the bags into the hole, then call the Public Works Department to report the need for a more permanent repair.

At the end of the six-month trial, city officials will decide whether to permanently incorporate any of the products into its pothole filling strategy.