There is a great deal more to fireworks than beautiful aerial patterns that light the skies on Independence Day. Those vivid displays of patriotic pyrotechnic wizardry are made up of carefully calculated chemical formulas that can be less than wholesome when absorbed at close range or as leftover precipitate matter in soil, air and water.
Just in time for this week’s annual celebratory sound-and-light shows, a report in a scholarly chemical journal tells of developments by researchers to make fireworks environmentally friendly. Think green to add to the perennial red, white and blue colors expected to dominate the scene.
The challenge for scientists - even explosives chemists such as Darren Naud and Michael Hiskey, who have worked at the government’s laboratory in Los Alamos, N.M. - has been to create fireworks that are relatively smoke-free as well as free of potassium perchlorate, an oxidant. Perchlorate, mixed with charcoal and sulfur fuel, is responsible for speeding up the fuel-burning process and achieving the fiery effects that awe a crowd.
Unfortunately, reports Bethany Halford in Chemical and Engineering News, studies have linked perchlorate to thyroid damage. Additionally, pyrotechnics often include other potentially toxic color-producing heavy metals such as barium and copper.
“At one time, mercury and lead compounds were used as colorants, but they were phased out long ago,” she writes.
Pyrotechnics also play a role in military operations, a fact that has led the Department of Defense’s Strategic Environmental Research & Development Program and Environmental Security Technology Certification Program to “sponsor an extensive series of efforts to make pyrotechnic materials friendlier on the environment,” she writes.
Mr. Hiskey, who spent 16 years at Los Alamos making what he calls “new energetic materials for the Department of Energy and the Department of Defense,” is well-versed in both the colorant and the propellant side of pyrotechnics. Red color results from the use of the chemical element strontium, blue from copper, gold from sodium, orange from calcium and green from barium, he says.
“Blue is tricky because, while most pyrotechnic flames have a tendency to be hot, copper does not emit well in a hot flame and also is not very strong,” he says.
Eliminating excess smoke as well as perchlorate was key to improving traditional fireworks, says Mr. Hiskey, who partners with Mr. Naud in a pyrotechnics production company called DMD Systems (www.angel firepyro.com) based in Ojo Caliente, N.M. Distribution is done through Lemaitre Special Effects in London, Ontario.
DMD Systems produces what it calls “theatrical pyro stuff,” for stage shows, rock bands and circuses. Most recently it sold Disney 400 of its 300-foot comets for a Wrestlemania show in Orlando, Fla.
The breakthrough, according Mr. Naud, was substituting a material called nitrocellulose that burns with very little smoke and “no fallout or residual combustion byproducts that are nasty.”
“We solved both problems at once,” Mr. Hiskey explains. “Nictrocellulose has its own oxygen, so it doesn’t require a lot of additional oxidants, and it burns very cleanly.”
The challenge in the future is to be able to mass-produce these perchlorate-free low-smoke pyrotechnics for use outdoors at a price that can compete with the popular and inexpensive Chinese imports. At present, a fireworks display using DMD products costs twice as much as the more conventional show.
Mr. Hiskey is optimistic, noting that shipping costs and safety matters have led to a decrease in the availability of low-cost China products.
“Shipping companies won’t take them out of China because of their bad reputation,” he says. “China has had some bad accidents in transportation. Fireworks are shipped in a container that becomes a giant bomb.”
On a local note, John Conkling, an adjunct professor of chemistry at Washington College in Chestertown, Md., and author of “Chemistry of Pyrotechnics: Basic Principles and Theory,” is conducting a four-day seminar on pyrotechnics on the campus beginning July 28 meant to appeal to anyone interested in energetic materials. Now in its 25th year, the program is the only academic course of its kind in the country, he says. For information, go to www.john.conkling. washcoll.edu.