Today I’ll be cutting out my pieces and get started sewing. First, let’s make some some changes to your cup pattern to work with foam.
As I mentioned yesterday, these techniques can be used with any bra cups. I’d recommend starting with a pattern that you are familiar with making. It can have any kind of seaming. If your favorite bra pattern is a frameless bra (Kwik Sew 3300 is one example of these), there are tricks to stitching in the channeling in such a way that doesn’t fold the foam back on itself. I couldn’t cover that here, but hopefully this tutorial will give you a good place to start!
Here’s the pattern I’ll be working with:
Sometimes I make these cups with a strap extension but for this tutorial I made a straight neckline to make things easier to follow.
[Edited to Add: The pattern I am using is not a commercial bra pattern for sale, but rather my own self-drafted pattern. If you are interested in turning a two-piece cup into a 3-piece cup, you might want to have a look at this tutorial.]
1. Retrace your cup pieces so that you have two sets: one for the main cup fabric and one for the foam. It’s really a good idea to trace what will be your foam pieces onto some kind of heavier weight paper (card stock, watercolor paper, manila folder, anything that keeps its edge will do).
2. On the foam cup pieces, you’ll need mark in and remove all seam allowances along these three areas: the seams that go across the cup, the underarm, and the neckline. Don’t remove the seam allowances where the cup joins the cradle (the wire seam).
Most bra patterns have 1/4″ (6 mm) seam allowances around all these edges, or don’t have seam allowances so you have to add them. I find it a good practice to keep seam lines marked in all my bra patterns so I can made accurate adjustments.
3. Next I consider how I want to finish my neckline. For this tutorial, I’m making a clean finish neckline, in which the cup fabric will roll neatly over the top of the cup.
On the fabric cup pattern, add a 3/8″ allowance to the underarm seam and the neckline. Half of this is seam allowance and the other half is cloth allowance for folding over the thickness of the foam.
There are other ways to finish the neckline. If you want to bind the entire neckline with something like foldover elastic, you would cut off the neckline seam allowances from both the foam and main cup pieces.
If you want scalloped lace along the edges, you’d also cut off the neckline SAs from both foam and main cup pieces. I also shave a little bit more off the foam neckline on top of that–about 1/8″–so that it doesn’t peek out above the scallops.
Now that all the pieces are ready, let’s get everything cut. When cutting from the foam, I gently hold down the pieces and trace around them with a ball point pen. (Sharpies and markers will bleed and make indefinite lines. Chalk and wax pencils don’t show up.)
Cut away the lines…
I also make tiny dots near the edge to mark the notch points (no snipping).
Foam Cup Assembly
1. To assemble the foam cups, butt the pieces together so that the foam lies edge to edge and is centered right under your presser foot. You’re going to zig-zag them together. You can use either a triple zig-zag or regular zig-zag. Whatever width you use, make sure it is wide enough to catch both sides of the butted seam.
As I am sewing, I am trying to gently butt the edges against each other without leaving a gap, or without forcing or squishing the edges together.
And here’s what it looks like stitched up:
2. Totally optional: At this point I can consider the foam cups finished, but sometimes I like to cover the inside seams. Covering the seams can add a bit of support to the cup and make it prettier. But don’t feel like this is necessary–there’s nothing wrong with leaving them uncovered.
I’ve tried a few different seam coverings. Narrow cotton twill tape makes a neat, trim covering but it has no give. I also tried a single layer of tricot seam tape but this was far too flimsy. My favorite is a wide bias seam tape that has been folded into thirds.
First I cut 3/4″ strips of tricot along the bias. Then I pressed each side under by a little less than 1/4″ so that the resulting width of the folded tape was just a smidge over 1/4″ (6mm). I centered this folded tape over my foam seams and stitched down each side of the tape.
You can also zig-zag down the tape (see the very top photo of this post). Sometimes stitching down either side can be tricky when you are first getting used to working with tricot. This stuff can be slithery and chiffon-like but it makes such a soft and delicate lining. I even use it as seam tape to cover delicate seams in silk dresses because it practically disappears and never ravels.
3. Now go ahead and assemble your main fabric cups.
At this point you should have two sets of cups, one from foam and one from your outer fabric. On Monday I’ll finish off by showing how I cover the cups and stitch them into the cradle. In the meantime, you can go ahead and assemble your band the way you normally do and add your hem elastic.
See more posts in the series Make a Foam Cup Bra.