Soft Parts FANGS' Guide to Sewing with Stretchy Fabric


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I'll start off by saying I am DEFINITELY no expert on this. I learned by trial and error and error and error. And I'll likely continue with the errors until the end of time but that's okay.

Stretch sewing is unfortunately a little more complicated in terms of skill levels when it comes to sewing. But if you break it down to it's most basic form, it's still sewing through two or more layers of fabric to create a seam just like sewing with non-stretchy fabric.

The first thing we're going to tackle here is machines.

This is a typical, mid range serger. This is in fact the model I have. I've had this machine for over 10 years and I've never had to have it repaired. I've literally sewn through most everything with it, including neoprene. This price here is in Canadian and is pretty close, if not a little less than I paid for it. I originally purchased a Singer, which, as it turns out was not a good choice. I am a big fan of Juki's (one of my sewing machines is also a Juki) but truth be told, they are almost always higher priced than is necessary just due to how their sales to North America happen. Having said that, I'd buy one again in a heartbeat because this has never let me down.


Serger's are typically divas. They are picky about thread and how much dusty bunnies have congregated on the inside. When they get in a snit and whispering sweet nothings to it doesn't fix it, completely unthread it and start over. If you must say something negative, don't say it in front of a serger. They absorb that bad juju and will eat your next project. Of course, with practice, all of that happens less and less but it still happens when you least expect it if you aren't paying attention. Sometimes it's a simple as the serger thread being too dry and dusty. While you don't have to buy the most expensive thread, do consider buying quality thread. Your machine will work much better.

A serger does a few things at the same time. You can use a serger with 2, 3, 4 or 5 threads, although most machines are only capable of going up to 4 threads, which is what my Juki is. The different thread combinations give you different stitches and different levels of "sturdiness" so to speak. I generally use 4 thread which I believe is called a basic or overlock stitch. A serger also uses 2 needles instead of one like a traditional machine when using a 4 or 5 thread stitch. you only use 1 needle for the 2 or 3 thread stiches. Two of your threads - those on the left hand side if you're looking at the front of the machine thread through the tension knobs and then through the needles. The machines generally will have colour coded paths for each thread. The two threads on the right of the machine are going to go through the tension knobs and down through the loopers. If you compare this to a standard sewing machine - the two threads on the left are much like the top thread and the two threads on the right that go through the loopers are like the bobbin.

The 4 thread stitch gives you a sturdy but still stretchy stitch whereas the 2 thread stitch gives you a much less visible stitch and would be used on fine fabrics like a chiffon to do a tiny rolled hem. The difference is that you'd want the sturdy 4 thread stitch on anything that is going to be under tension, like a seam and especially on a seam on a close fitting garment.

When sewing, your two looper threads will form the zig zaggy stitch that goes over the end of the fabric (more on this in a moment). The left needle will catch the looper threads and lock them in. The right needle does an extra stitch that gives your seam more strength. Most commercial garments are going to be made or finished with a serger. If you've ever had a seam let go, you've likely seen that it doesn't always rip right open, but sometimes only the first row of stitches does. That's where that extra line of safety stitch comes in to make your seam more durable. Plus, it helps take some of the load off of the most outer line of stitching which helps to prevent any unwanted display of your undies.

Take a moment to look at the shirt you're wearing right now. If you look at the inside of the seams, you'll see threads that wrap around the seam and you'll see straight stitches along the inner edge of the seam. That's what a serger does. On the outside you'll just see the seam but no stitches. If you look at the hem on the sleeve or on the bottom of your shirt, you'll see similar looking zig zags on the inside, but the outside will show 2 or 3 lines of straight stiches with no seam. This is done by another machine called a cover stitch. You won't be able to do that with a regular serger on it's own but never fear, there are other ways.

The zig zag part of the stitch also serves the purpose of preventing fraying of the fabric. I use my serger to serge all fabrics, even non-stretch ones, before sewing so that my seams end up looking finished and professional and I don't have to worry about the fabric fraying. may be thinking at this point - how do you consistently get your looper threads to encase the edge like that. Must be some magic perfect straight cutting and perfect straight sewing, right? Well, those definitely are things to strive for but the real magic of a serger is that it also cuts as it sews. There is a knife that is located right along the side of your needles. As the fabric passes through it first goes through the blade and gets cut and then the needles take care of getting those threads to loop around the edge. The knife makes things looks really great but it also means things can go sideways fast. You cannot let an item "out" should it be too small. When using a traditional machine you can pick out your stitches and sew a little closer to the edge to make the garment bigger, but with the serger, once it's cut, there is no going back. You can disengage the blade but then you are negating some of the purpose of a serger in that you'll still have a raw edge.

I highly recommend watching a bunch of YouTube videos about the specific machine that you'll be using. As well, look up blogs, like this one I found tonight, that set out examples of what each type of stitching looks like etc.

Serger Stitches

I learned before there were a zillion YouTube videos so I have a big collection of books that I reference. I also have made sure to keep the manual that came with my machine at hand for any information I need about how to do something specific to that machine. One option to keep your eye on is the Humble Bundle. I think once (maybe twice??) a year they will offer a giant bundle of books about costuming for incredibly low prices and they usually will include at least one or more general sewing and tailoring books. You choose the price you pay - either the lowest price possible or additional amounts as you deem fair, and some of that money ends up going to charity and you get a great digital costume construction library.

I'm going to update this post over the next few days to include a few more photos. The next posts will include what you need if you don't have access to a serger, types of stretch fabrics, fit, and patterns.
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All stretchy fabrics are not created the same!

Do yourself a HUGE favour and know what you're buying. You do not want to spend all of this time learning how to sew to create an undersuit that snags and runs like cheap tights the first time you pull it on.

First things first - there are 2 types of stretch - 2 way and 4 way. This is a tad deceiving and I must admit that many years ago when I started working with stretch fabrics this threw me for a loop. 2 way stretch means it stretches in 2 directions - to the right and to the left of centre. 4 way stretch means that it stretches to the right and to the left as well as up and down. Typically I look to work with 4 way stretch, but that isn't possible with all fabrics. If it has to be a 2 way stretch, you'll want to ensure that each pattern piece is cut with the direction of the stretch going across the area requiring the stretch. For example - for pants, you'll want to ensure that the stretch is going horizontally so that you have stretch for movement and fit. If the stretch is only going vertically, you'll have a tough time with mobility.

The other consideration is the amount of stretch that the fabric has. A fabric like a glossy PVC whether 2 way or 4 way stretch is going to have minimal stretch, but also won't stretch out and stay stretched out in areas like elbows, knees or your booty. For fabrics like this I make sure to make the item big enough to fit me without needing to be stretched and that way all of the stretch is reserved for movement and getting it on and off. Examples of this type of fabric are (Catwoman only in the below photo):


My Catwoman here was made with a 4 way stretch PVC and then I sewed in the white stitches with an elastic thread so that it would stretch as well with movement and not pull on the holes too much. More on the Harley fabric in a moment.


I made my Selene using the 2 way stretch PVC fabric. This time the challenge was the "floating" gun holsters that the arrows are pointing to. I couldn't find a better photo but basically there are no visible straps to hold them up so we put a piece of sintra on the inside that was shaped like the curve of my leg and bolted the holsters on. So it was important that the fabric choice was sturdy enough to put up with not only the weight of the holsters but also the pressure of pushing the guns in and out of those holsters. The lack of stretch vertically helped with it being more sturdy specifically for this purpose.

When I made the Harley Quinn, I used a 2 way stretch called Jumbo Spandex. Unlike the 2 way PVC however, this Jumbo Spandex is super stretchy but won't get baggy after you have it one for awhile. The stretch is sewn horizontally for a second skin like fit. This a thick, heavy weight spandex that is used in the creation of stuff like wrestling singlets etc. It is durable, doesn't snag easily and can be hand washed.

When I made Alice from Resident Evil, the bodysuit had to have the feel of a pair of long johns. It needed to have a little drape and a little bagginess to it. It wasn't necessary for any of it to be able to stand up to the rubbing of armor or to be stable enough to hold up anything like the holsters on Selene. For this I went with a pretty basic cotton jersey knit. The longer I wore it, the more "lived in" it looked. This had a 4 way stretch and raw edges to replicate it being cut. Given that the suede shorts had to go over top of this onsie, I made the bodysuit first and then made the shorts to fit over the bodysuit.


My go to for anything that needs to be under armor is a 2 or 4 way stretch fabric called Ponte de Roma. It is typically a much sturdier, thicker stretch fabric. It has a lot of stretch so the sizing is far more forgiving than say a PVC is and it stands up well to the rubbing from armor. It does not snag or run and it does not stretch out to leave bagginess after you've worn it for awhile. You can just throw it in the washing machine and it and hang to dry. My Bo Katan undersuit is a one piece bodysuit and then a second vest over top of that, all out of the same Ponte de Roma fabric. It is a 4 way heavy Ponte de Roma. All of the armor velcros on, although I think my next Bo Katan (Mandalorian version) will use magnets. The fabric does not wrinkle or pill. It has a soft feel and only comes in a matte finish. And being that it is 67% Rayon, 29% Nylon and 4% Spandex, you should be able to dye it with something like Rit Dyemore Synthetic Fabric Dye, although I have never attempted that.


I've saved the beast for last - Neoprene. Don't be confused by a really common fabric out right now called Scuba. They are not the same. Scuba is pretty cool but I'm not sure you'd want to make an undersuit out of it. Neoprene is often asked about to use for undersuits and people always jump in and say something like "only if you want to sweat too death". This is accurate, but it's also not the complete story. Neoprene is a stretch fabric, however, it has minimal stretch, similar to a PVC fabric. I believe they are 4 way stretch. The seams are sewn together using a couple of different techniques like flatlocking or blind stitching but all result in the same end goal of encasing the seam as flat as possible. I'm sure there are a zillion reasons for this but the hard lesson I learned is that rubbing from the raw edge of neoprene will make you bleed and leave a scar.

This photo is harder to share because there is so much wrong with this Zam. Some day I'll finish it properly. Not only is it the most expensive costume I've ever made but it also taught me the most about learning all kinds of new techniques like weathering, sewing with leather, leather dying and sewing neoprene. I built it in 2009. It's also the suit that gave me scars on the inside of both knees. This suit is like wearing a giant elastic band. It is a work out to get it on and a constant work out moving around in it. Neoprene is no joke. But the original gear is made from it is what is. I sewed the inside seams the same as I would any seam. This left the raw edges to rub against my skin. We did an indoor event at a mall so I decided it would be too hot to wear under armor under it as I normally did. The seam basically rubbed a divot in my skin. This specific neoprene was custom made to have a lycra that was dyed to match the movie version laminated to the surface of the neoprene so it is incredibly hot to wear. I also made some of the suit so it was slightly stretch while on - specifically in my forearms and wrist areas. Over time this constant pressure causes numbness in my thumbs. This was how I learned how to fit a garment like this to fit without stretch so that the stretch is reserved for movement. All of this to confirm that neoprene is not a good choice for an undersuit. It looks cool but that's where it ends.


What you are using the fabric for makes all of the difference in what you should look for in a fabric. Take a trip to the fabric store and check out all of the varieties of stretch fabrics. Give them a tug in all directions to see if they are 2 or 4 way stretch and how much stretch they have. Watch how the fabric comes back in to shape (or doesn't) after you stretch it. On patterns made for stretch fabrics, there will be a measuring tool on usually the envelope flap where it is recommended that your stretch fabric have a specific amount of stretch to it. If your chosen fabric has less stretch, you'll want to make your garment larger than the recommended size. You can always take it in a bit if you make it too large. Look at the cut edge of the fabric for signs of it running. That's not to say that all fabrics prone to runs will have runs in them on the bolt BUT if you happen to see any.....RUN.

If anyone would like, I'm happy to mail you out little samples of the the various fabrics. I think I still have all of them to do so. If that helps you in your journey to get to know stretchy fabrics, I'm happy to do so.
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Reserved for advanced techniques - will be updated over time

Lots of times we need to make undersuits that have extra detailing on them. The biggest thing to keep in mind is how what you are doing may limit the stretch. As soon as you sew a regular straight line through a stretchy piece of fabric, you limit or completely remove the stretch of the that fabric. I've played around with some solutions to this.

In this example - Ultraviolet from the movie of the same name - I combined a semi stretchy faux leather with a really stretchy Jumbo Spandex to match what the original suit had. In order to get the faux leather attached, I sewed it on with a regular straight stitch which means I removed that stretch over that section of my leg. However, because the rest of the leg was the super stretchy Jumbo Spandex, I made the legs slightly bigger that I normally would and the Spandex took care of the rest. I had full mobility and nothing was straining against the stitches as I moved.


Shae Vizla has a lot of extra detail on the undersuit - this version being the concept art from the game KOTOR. I'm not sold yet on what I did here but it worked well enough until I figure out the next solution. I made my undersuit using Ponte de Roma. My armor is resin so it's pretty heavy so I definitely needed a sturdy fabric underneath. There is also a lot of armor so I needed to be wary of the rubbing of it along with velcro and strapping used to hold it all up. For the details, I used a stretchy heat transfer vinyl. It has peeled slightly under the thigh armor but otherwise, surprisingly, has held up okay. I think my next version will incorporate something like I did for Ultraviolet along with some spacer mesh to give detail with dimension. I think that this technique will be the most helpful for the detailing on Halo undersuits.

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