If you're wondering which type of balloon is best for your next party or celebration, most balloons fall into two general types: Mylar and latex. Both balloons may be filled with helium, but the amount of time they float is significantly different. Mylar balloons also should only be used indoors due to a potential unique safety hazard.
Mylar Balloon Basics
Mylar balloons, also known as foil balloons, are made from nylon with a metallic coating. These balloons look like shiny silver metal when plain, although they are often printed. Unlike traditional balloons, foil balloons are not porous, so air does not leak out of them easily, as long as they are properly sealed. Mylar balloons are also not biodegradable, as they're made from synthetic materials.
Latex Balloon Basics
Latex balloons -- the old-fashioned stretchy balloons you can blow up with lung power or helium -- are made from a liquid form of rubber. Inflated balloons made of this natural material contain tiny holes or pores that allow air inside to escape over time. Unlike Mylar balloons, latex balloons stretch and expand as they fill with air or gas. Filling a Mylar balloon, on the other hand, is more like filling a plastic bag with air -- stretching is minimal, if present at all.
Since both Mylar and latex balloons hold helium, both are used at parties and to commemorate special occasions. Inflating two balloons with the same amount of helium -- one balloon each of latex and Mylar -- and tying them with a ribbon secured to a weight results in both balloons floating in similar fashion for a while. The latex balloon slowly loses air, so it floats for 12 to 40 hours on average, depending upon the its size and the temperature of the air. The Mylar balloon may float for more than two weeks, as long as it is sealed properly.
Since Mylar is a type of metallic foil, it conducts electricity. A helium-filled Mylar balloon indoors is generally safe, but outside it could be major cause for concern if it escapes. If the balloon becomes trapped on power lines or electrical equipment connected to the lines, it could cause an outage. Regular latex balloons, on the other hand, generally are not cause for concern when it comes to electricity. If you're using latex balloons outdoors and you plan to release them, be sure that any ribbon tied to them also is not metallic, or they could cause electrical issues as well.