For balloon arches, can the balloons be tied individually and then put together? Will you need helium for making balloon arches or can I blow by mouth?
You need helium to lift your arch, if you blow it up by mouth, it will not fly. Air filled balloons (and arches) can be used with frames - to keep them in the air and the shape you want. If you have someone to bend pipes for you, I can tell you which ones to get to keep the cost to min.
Keep in mind that you would need at least 100 balloons blown. Do you want to blow up that many by mouth?
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