Mystery of the Concave bra cup?

I posted this to Bhuz today but since I have a fellow few bellydance costume designer people on my Friends list - why not ask you folks as well.


I'm used to costumes that I make for myself - and the bras fit perfectly.

But... I now own a few second hand, "professionally constructed" slightly used bedlah and they have the rigid hard cup as the base under the fabric & sequins and trim. They can easily be forced back out into the correct rounded shape but ... they seem to default to cup with inverted or depressed areas after a few minutes. This seems to happen especially in the lower part of the cup, but sometimes in both the top and bottom of the cup. Any idea what is going on here?

I tried heating the cup (with a hairdryer) and binding it around an appropriate shape to hopefully reform it but - after I remove it from the styrofoam balls it eventually goes back to it's depressed state. It's not gravity as I've tried storing the bra with the cups either direction.

This isn't a matter of stuffing or filling the bra - as that seems to make no difference. And one of these is already an exact fit. I -need- that space. This is happening in all 3 of my hard cup bras. The 4th... was such a bad fit that I stripped it and remade it onto my own bra form - Having taken apart two of them I know what the innards look like.

So.... is this just something particular to this bra construction style? poor storage? age of costume?

I'd appreciate any suggestions or ideas for a solution.