The attempt to make fireworks that ended in an explosion at Murch Elementary School on Monday, seriously injuring two 9-year-old boys, did not comply with accepted safety standards and procedures for mixing the kinds of combustible materials that were being used, specialists said yesterday.

The experiment, conducted as part of a special summer enrichment program for gifted and talented students, called for students to mix and grind several substances to make hand-held fireworks called "sparklers."

The students were injured when a bowl of the substances -- potassium perchlorate, sulfur, charcoal, iron powder and aluminum powder -- exploded. Two 8-year-olds also suffered minor injuries.

John Conkling, executive director of the American Pyrotechnics Association, said professional manufacturers of sparklers usually make sure that combustible materials are moistened with water before mixing and grinding them, to avoid any possibility of an explosion.

"The sparkler composition is prepared in a water slurry which renders it much less prone to ignite. In a dry form, there's definitely potential for ignition and a fairly violent output," said Conkling, who also serves as chemistry professor at Washington College in Chestertown, Md.

Commercial fireworks manufacturer Charles Shivery, president of Elkton (Md.) Sparkler Co., said, "We start with barium nitrate [a slow-burning combustible substance] as our oxidizer. But we don't normally mix the composition dry. We mix it with water in a mixing machine and mix the rest of the substances with it, so we never have a dry, flammable composition. Then, the wire is dipped down into the wet composition . . . . It won't even burn until it dries. By then, it's a hard surface."

The chemicals used in the Murch experiment, which school officials said was supervised by instructor Lou Jagoe, are not typically used for making sparklers, Shivery said.

"Sparkler compositions will not explode, period," he said. "The composition they were working with is very similar to firecracker powder, rather than typical sparkler compositions."

Michael Nickens, 10, one of 14 students who participated in the experiment, said, "The powders were put into two bowls dry and then they put some kind of flammable liquid on it. We were very excited about it. Everybody said, 'Oh, let's make sparklers.' "

One of the seriously injured boys "took the bowl and started shaking it and banging it," Michael said. "He said, 'Oh, nothing's going to happen,' and it exploded right in his face."

After the explosion, "his fingernails were gone and skin on his face was peeled and his hair was burning," Michael said.

The program under way at Murch, called "Summer Discovery," is not run by the school system, although D.C. school officials approve such programs before they are allowed to be conducted in school facilities.

D.C. School Superintendent Floretta D. McKenzie has called the experiment "inappropriate," and said there has been no decision on whether the school system will attempt to take any action against Jagoe or the director of the program, Charles Butta.

A chemical safety officer under contract with a federal government agency said yesterday that the experiment "violated all the standard safety measures prescribed in federal chemical manuals."

The officer, who asked not to be named, said the materials used in the experiment are "highly explosive . . . toxic and very dangerous."

The two injured boys were reported in serious condition yesterday at Children's Hospital.

Butta, a doctoral candidate at American University, said yesterday, "I wouldn't do that experiment again. It should've never happened."