One thing I've noticed about me and Pinterest -- I pretty much just look at the pictures and look for key words to see if there's any special materials used and then I kinda do it my own way. (Probably not the best idea, but it worked.)
If you want to give it a try, the materials I used were:
(9 inch for large/water balloon size for small)
Hanger (for drying)After blowing up and tying several of the smaller water balloons into the size "egg" we wanted, we tied a twist tie to the stem of the balloon. Then, we simply wrapped the thread round and round the balloon every which way and I kinda dabbed the glue on as I went around making sure to cover the "top" and "bottom" part of the egg as well as the sides. For the small balloons I used one full strand of embroidery thread (.35 cents at craft stores). The bigger eggs used 2-3 strands. After you cover with the desired amount of string, I dabbed the fabric stiffener really well all around the balloon covering all threads.
We let ours dry overnight, but I think they could be dry in 4-6 hours. Now the fun part... Cut the stem off each balloon and watch the balloon deflate until you just have your pretty egg shaped threads left. (I would recommend doing it over a craft table or sink as pieces of dried stiffener do flake off as you are doing this.)
We also made bigger eggs using two or three of the full strands of embroidery thread. These were fun and my girls are planning to make round shaped ones to hang in their rooms. Whatever shape your balloon is, that's what you will end up with.
Voila!! We liked it so much, we are mass producing them over here and going to make some more later today!!
*I think the Stiffener is basically glue and water and I believe you could try mixing those and get the same affect!