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"     Just mention the words &amp;quot;Fourth of July&amp;quot; and a wealth of sights, sounds and smells comes to mind: barbecue cook-outs on the lawn, warm afternoons spent with family and friends, the flutter of Old Glory. But perhaps none is more exciting than the booming explosion of fireworks glittering through the night sky.   Nearly a decade ago, PM reported on the crafting and history of fireworks with a profile of the Grucci family, which we called &amp;quot;America&amp;#039;s First Family of Fireworks.&amp;quot; (The Zambellis staked their claim for the international title when we caught up with them about the science of fireworks last Independence Day.)   Fireworks can be traced back to China, where the first explosives were created for entertainment and ceremonial use. Historians believe Marco Polo brought the technology to Italy in the 13th century. The Gruccis used modern forms of both Asian and Italian-style fireworks as their distinct casings produce different visual effects. &amp;quot;The spherical [Asian] shells are needed to produce perfectly symmetrical chrysanthemum bursts,&amp;quot; whereas &amp;quot;creating a Osplit comet and other multi-break effects requires the use of cylindrical Italian shells,&amp;quot; PM wrote. Originally, fireworks were only white and gold, but to produce all of the colors we have today, the Italians began adding trace amounts of metals that burn at high temperatures in the 19th century.   In the the 1997 feature, the Gruccis insisted to PM that the real art of fireworks is in the timing. The shell should break at the height of its trajectory, when it momentarily hangs motionless in the sky. &amp;quot;If it explodes too soon, some of the visual drama can be lost. If it breaks too late\u2014on the down slope of its trajectory\u2014things could get dangerous,&amp;quot; PM warned. Because shows often require the use of several different-size shells, time-delay fuses are the key to making sure each is kept on cue (though as the Mythbusters know, even that can prove difficult). Fireworks are at once a marriage of science and precision, but when it comes to the Fourth of July, we can&amp;#039;t help but be captivated by the artistry of these explosive celebrations. \u2014Daniel Tam-Claiborne   RELATED STORIES \u2022 TECH WATCH: With Green Fireworks Not So Green, Plan for Eco Alternative  \u2022 Q&amp;amp;amp;A: Inside the Synched-Up Science of Fireworks  \u2022 THIS IS MY JOB: Pyrotechnic Computer Geek  \u2022 THIS WEEKEND: 20 Ways to Do the Fourth Right (and Safely)  \u2022 TIME MACHINE: More Modern Updates on Classic PM Covers!   "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/science/a3421/4271573/>