I'd recommend to use either 1/4 inch or 1/2 inch aluminum rod for the frame. Draw the stiletto shape on a large piece of cardboard, then bend the rod into shape.
You might want to use a pipe bender to help you shape the frame.
You'd then add your balloon clusters to the frame, and pack them tightly, so that the frame doesn's show.
Option #2: Without a Frame
You can also create the shoe by simple using a garland made of 4-balloon clusters, and tied together with 260Q balloons.
Follow this video tutorial for step-by-step instructions:
Which Size of Balloons Should You Use for Your Stiletto Sculpture?
Use 5 inch balloons for the heel, inflated to 3.5 inch at the bottom and to 4 inch at the top.
Use 9 or 11 inch balloons, inflated to 7 inch.
The above are the sizes used in the video. The larger the whole sculpture, the bigger you can inflate the balloons. Use smaller balloon sizes for smaller sculptures.
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