Apologies for the late reply, but I was on Easter vacation.
I am afraid there is no easy way to replace a popped balloon in an arch or column. You will have to remove the cluster from the frame or line, and replace the duplet where the balloon popped with a complete new duplet. Then put the cluster carefully back in place.
So your best bet is to make sure that balloons rarely pop. Here are some tips for preventing balloons from popping:
- Use only high quality latex balloons (e.g. from Qualatex).
- First over-inflate your balloons, then deflate and inflate again, now to their proper size, using a balloon sizer.
- If you decorate outdoors, or in rooms that heat up, make sure to under-inflate your balloons (8 inches for 11 inch balloons, 9 inches for 12 inch balloons, etc.) so that the heat won't expand them to the point of popping. Some balloon professionals report best results when they use 16 inch balloons inflated to only 10 inches.
- Place table plastic on the floor underneath you column or arch, as even the tiniest bit of sand on the floor can pop the bottom balloons.
If you make a purchase through a link on my site, I may receive a small commission at no extra cost to you. I only recommend products that I believe to have good value (affiliate disclosure).