I have a red one here that I am planning on using on FSL earrings and see if the color stays when I rinse out the wss. If it works I'll make more pairs but I bought regular mylar made to be washed for another project. I am terribly behind in embroidery.
I have used pieces of a mylar balloon for designs, but NOT on a design that will be washed. The color on these balloons washes off. I used it on a bookmark and on a design for a card. Haven't tried it on Christmas ornaments, but that might work.
I did! I left the balloon all together (the 2 layers) and put a piece of stabilizer on the back. I used it to make the halloween earrings from Stick and was pleased with them. Hope that helps.