We get a lot of requests for private classes to sew swimwear. While my experience was very limited, I wanted to explore this new fabric to be able to help our private class requests.
Personally, I find sewing swimwear quite intimidating. The projects comes super quick together because the pieces are much smaller and very few in comparison to jackets for instance. I learnt more about my body and size. For instance, most of my bust measurements comes actually from my back due to my broad back. The very first bikini came out way to big. Also, I mostly make garments that require a bra underneath, so measure yourself naked since your swimwear is supposed to be a second skin.
Let's dive into what I have learned and what tips I can give you.
1. PURCHASE THE RIGHT FABRIC.
Choose fabric that has 4-way stretch and a spandex content of at least 10%. Make sure that your fabric has lots of stretch and also a great recovery. Stick to a fabric that can absorb the water and still hold up. Look out for fabrics that specifically labelled for swimwear.
Try to avoid natural fibres like cotton and linen. Fabrics should be nylon and spandex blend.
2. CHOOSE THE RIGHT LINING.
Lining fabrics are an important part of your swimsuit. It's the fabric that faces your skin and provides added support and stability to your swimsuit. For ready-to-wear swimsuits, you will often find thiner nylon lining fabric. You can also self-line with your swimsuit fabric, or a different colour - maybe make it reversible.
For my bikinis, I have tried both versions. Since I have made the same bikini in a few fabrics, I personally preferred the thiner lining fabric. The same fabric on the inside, feels bulky and I feel less support. I also cut the lining fabric 1/8" smaller than the outer fabric. This worked really well and gives great support and coverage; and a nice finish around the edges of your swimsuit.
For the triangle version, I didn't mind the same lining fabric. I guess the triangles are cut a little smaller than the pattern I used.
3. USE SWIM-SPECIFIC ELASTIC.
All swimsuits require elastic, avoid using standard polyester elastic (the one you put in elasticated waistbands) because it will not hold up to chlorine and salt. Instead, look for chlorine-resistant rubber elastic. Make sure it’s labeled specifically for swimwear!
4. MEASUREMENTS AND THE SIZE.
Swimsuits are harder to toile (you can’t use a cotton muslin, after all) but the good thing about swimwear is that you often don't need a lot of fabric but your local shop might only sell by the metre. So you can make your toile in the same fabric as you are planning to use and still have enough fabric left to make the final version.
When choosing a size, remember that you will have negative ease - meaning the finished measurements are smaller than you own measurements. Don't worry - this is correct. Your swimsuit is supposed to fit snuggly, like a second skin.
Based on my personal experience, it is best to go down in size as you want the swimsuit to hug you and stay up. Hence a toile is a good idea, as always.
5. CUTTING YOUR PIECES.
Swim fabrics can be very slippery. There are a few things you can do to make cutting less difficult. Try to cut your pieces on a single layer. If you don't have a rotary cutter, mat and pattern weights yet, this will be the perfect time to invest. Try to cut with the printed side of the fabric facing up, so you can be precise about pattern placement and avoid a misplaced flower or design feature.
As always, pay attention to the grainline when you are cutting your pieces.
Swimwear fabric is so stretchy, pattern designers carefully layout the pieces in such a way that the intended stretch direction matches the needs of the swimsuit design. This will most of the time be along the grainline (parallel to the selvedge). Take note of how the pattern wants you to cut the pieces and make sure you are doing so accordingly.
6. NEEDLES, THREAD, AND PINS.
Make sure you are using a stretch needle that is suitable for the weight of your fabric. As always, test the needle at some leftover scrap fabric.
I used a jersey needle, that has a ballpoint. Some people use a stretch needle instead. Try out both first before you damage your fabric or get frustrated with skipped stitches.
If you have special pins for stretchy fabric, use them. If you don't (like me), you can use your regular needles just be careful you don't damage (snag) your fabric. I use shorter glass-head pins and didn't have any trouble.
For thread, stick with polyester which will hold up best to chlorine and salt. Try to use a high-quality thread brand. Lower quality thread can cause skipped stitches, even when you are using the correct needle.
A serger or overlocker is not necessary to sew swimwear, but it can be used in combination with a sewing machine. If you have one, you can also try using woolly nylon thread in the upper and lower loopers of your overlocker. This is a great way to provide extra stretch to your swimsuit.
I tried both, regular thread and woolly nylon threads in my overlocker, and have noticed the difference when stretching the swimsuit. I also found that the woolly nylon thread is more comfortable to wear. So if you have an overlocker and can get nylon threads, I would use them. You will have to make some adjustments to your overlocker settings.
7. USE STRETCH STITCHES.
Your stitch needs to stretch, just like the fabric. Otherwise your stitches will break when the fabric is stretch.
Overlock machines are a popular choice for the inside seams of swimsuits, but you can sew your swimsuit on a regular machine. Be sure to use a zigzag stitch, triple zigzag stitch, and lightning bolt stitch. The pattern instructions might recommend specific stitch settings. As always test your choose setting first to avoid any mishaps.
Just like other knit fabrics, swimsuit fabric doesn’t fray, so raw edges are fine. Most seams might even be hidden and enclosed under the lining.
8. DON’T STRETCH THE FABRIC.
You want stretch fabrics to have some give when you wear them, so try not to stretch or pull the fabric taut as you sew. This will distort the final shape of the swimsuit and you will have wavy seams.
When you are attaching binding pieces or elastic to your suit, you’ll need to stretch those just enough so that they are the same length as the main fabric, but not any further. Keep in mind, you don't want to add gathers or puckers, so this is what I find most difficult, finding the right amount of stretch of the elastic. The first once, the instructions told me just only keep the elastic taught but you have stretch it very little. Stretching the elastic will help your pieces to stay up and against your skin.
9. SKIP THE IRON.
Synthetic fabrics are likely to melt under the heat of the iron. I didn't use the iron once during the making of my swimsuit. For flat edges and neat finished, you can finger-press, understitch as well as top-stitch using a stretch stitch. Even in places that the pattern didn't ask for understitch, I still did one and it turned out great.
10. CREATING SUPPORT.
Support can be a concern when sewing swimwear. The swimsuit other than stay up, should also give you support, especially if you have a bigger bust. In my first version, the tankini, I sewed in cups but the cups were too small for the triangle bikini top.
Foam cups are a popular option is ready-to-wear swimwear. Foam cups offer light support, and modesty in a wet swimsuit. If you plan on using foam cups, be sure to purchase ones that are specifically meant for swimwear. Foam cups intended for lingerie may not stand up to chlorinated or salt water, and may absorb large amounts of water. I tried using foam cups but the cups ended up being to be for my bust and too small for the very first bikini I made.
Underwire is another way of achieve additional bust support. Not all swimsuits are designed to be compatible with underwire. If you know that this is a feature you must have in a swimsuit, look for a pattern that features cups that are attached to a full band. Purchase underwire that corresponds to your bust size and the size swimsuit you are making.
Stays do not actually support the bust in the case of swimwear, they do support the swimsuit by making sure it doesn’t end up around your waist. Stays are applied in a very similar fashion to underwire.
Find more information on how the support is sewing on Seamwork.