You want a foam cup, but haven’t access to seamless foam cups? You can still have the look by using cut-and-sew foam. This is a foam cup that has been attached at the cross cup seam by stitching the upper and the lower cup together. This is most useful for making foam cups under lace or other thin fabrics or for making strapless gowns, strapless bras or bustiers.
The “secret” is the foam itself. I call it “pre-finished padding” because the stuff I use all the time has an 1/8” layer of foam bonded between two layers of a nice quality tricot. There is no need to put a lining inside these foam cups when they are finished because of the inherent tricot lining already built in. There is also “swim cup foam” which has a different fabric front and back, and while it is great for swimwear (it actually molds with the heat of an iron) I don’t consider it a great choice for garments. So use swim cup foam for swimwear and use pre-finished padding for any other garment. The techy name for the pre-finished padding is Poly-laminate foam padding.
The pre-finished padding comes in standard white, black and nude, although I keep hearing rumours that the white may be discontinued because of its tendency to turn yellow in chlorine, and customers are complaining. ANY white will eventually turn yellow in chlorine, but we can still use the foam in garments that won’t be spending most of their day in chlorinated pools.
The foam is so easy to use, it’s almost scary. It works better than most fabrics for doing manipulation of the cups for style changes, and is, in fact, the first step in the process of changes to the style lines of any cup.
As with anything in the bra industry, there is more than one way to use any given product. There are three slightly different methods used to stitch the foam cups and the method you use depends on the look you are trying to achieve, and the fabrics you are using with it.