i weighed a 1 foot lenght of bare copper 12 guage wire at the post office and it weighed .30 ounces.

that means 100 feet of bare copper 12 gauge wire would weigh 30 ounces or 1.875 pounds or 852 grams.

12 guage wire is .0808 inches in diameter and 15 guage wire is .0571 inches in diameter, and when you caculate the area of the wire the 15 guage wire is half the area of the 12 guage wire so 100 feet of 15 gauge wire would weigh 15 ounces, 0.937 pounds or 426 grams.

that jives with some tables i found on the internet that say 12 guage copper wire weighs 1 pound for every 50.59 feet, and same for 15 guage wire which weighes 1 pound for every 101.4 feet.

now i checked out some data on weather balloon too. in the back of my mind i though the typical weight of a weather balloon payload was 100 grams or one tenth of a kilo, .22 pounds, or about 3.52 ounces.

the weather balloons i found on the internet listed gross lift weights of 60 to 3950 grams and free lift weights from 50 to 2000 grams. so a weather balloon should easily be able to lift a 400 to 1000 gram wire 100 feet into the air.