OK I am fairly new to gumpaste flowers, and I am NOT good at taping really thin wires. I was in Hobby Lobby looking for pre-taped wires, and they did have them, but they were pretty thick (probably did not split the tape before covering). I mentioned this to the sales girl and she asked why I couldn't just use the green coated wires without taping them. I realized the only answer I had was because I read you have to tape them, but I don't really know why. What is the purpose of the tape?
I am by no means an expert, but from my experince, the tape helps old the gumpaste on the wire and in place. When I made some leaves for my poinsittas on unwrapped wires the leaves spun around on the wires.
Instead of looking at local craft stores, I'd suggest order from cake supply websites. They sell all kinds of sizes of wires that are wrapped in white or green, ready to use.
Unwrapped wires--or even the cloth/thread covered wires--will rust immediately upon exposure to moisture in the cake--YUCK!
Not that wrapped wires should ever be put directly into a cake--no matter WHAT we see Duff & Buddy do......so, that's one reason to wrap with tape--it's pretty moisture proof.
As TS said, another reason is to stabilize the gum paste item on the end of the wire. The tape definitely keeps them from spinning & sliding.
The wires available at the craft store are generally cloth/thread wrapped. They're really not for making gum paste flowers because the thread releases as soon as it gets wet.
The best wires are the paper wrapped wires from Japan---Sunrise is one brand--and you can order those from a variety of cake deco site, including globalsugarart.com
Another reason is that depending on what wire you are using the wire could contain food safe metals so wrapping the wires in tape or sticking them in picks or straws helps to avoid the metal from coming into contact with the cake.
Thanks all. That makes sense.