There are lots of reasons people chose to have foam cups in their bras. For extra “lift”, nip protection, and shape. I like sewing them into all my bras, swim tops, and dress bodices that are fitted so I don’t have to bother putting on a bra-its all included!
There are also different kinds of foam cups. Some are pre made or you can buy the foam and make them yourself. It is cheaper to buy the foam and make them yourself, but those are typically one layer (think swim cup). I like all the oomph I can get so I go for the push ones that are pre made. I off set my cost of buying them pre made by buying a dozen at a time (remember the list of how often I use them?!) I like the extra push up ones from SewSassy.com
First thing you want to do is make sure you have a left and right! Once you have a set, cut off the little tab at the top. Then you want to center them on your lining of your bra/top/whatever (I’ll say bra going forward since thats most typical and to keep it simple) you are sewing them into. You want to place your lining piece right side down (mark the center). Plan the cups curve side down. Then place your foam cup pieces evenly from the center. I like to place mine a little more towards the bottom since I use the push up kind that way I get the lift I want. Placement is really personal preference, you’ll find what you like best.
Then you will want to start with a regular stitch/backstitch to lock your stitch in and switch to a zigzag stitch. I like to try to get my stitch to go on and off my cups that way theres no weird curving/warping after lots of washes. I usually don’t get a perfect stitch the whole way, thats ok, thats just what I aim for. I also *very* slightly pull my fabric as I stitch the cups on that way the fabric is nice and tight when its all complete.
Now your cups are all sewn onto your lining! Time to continue making your garment!
Here is a link to my favorite (at this moment) maxi dress I like to make with these cups in the bodice Maxi Dress is the Leggings of Summer