Technical Stuff!

What is circular knit? What's difference between lycra and spandex? Is polyester preferable to nylon? What does 'gsm' mean? And what is wicking, anyway??

Wow - there are a lot of things we seem to need to know about sportswear fabric! So I thought I would try to bring some of these little details to light in some nice friendly language.

Nylon vs Polyester

Both nylon and polyester are non-absorbent (hydrophilic) textiles. Nylon is ever-so-slightly more absorbent than polyester - that's why super-bright prints usually have a higher nylon content, because the dyes are more easily absorbed. Polyester, on the other hand, doesn't like to hold moisture at all, which is why is it so great for exercise - no sweaty fabric clinging to the skin. However, it is not just the fibre content, but also the yarn construction and the weave that contribute to a fabric's ability to move moisture. Which leads us to....

"Moisture Management" (that's wicking, folks!)

 Wicking - scientifically known as 'capillary action' - is the ability of liquid to flow in narrow spaces in defiance of gravity. Imagine a sponge in a puddle of water - the water gets sucked up into the sponge. That's pretty much how wicking works. Here's another couple of big words: intermolecular forces! Sounds like something Antman would know all about. Wicking fabrics are made in such a way as to create greater opportunity for that capillary action to take place. Bascially, when you're sweating it out on the bike or going for a run, a wicking fabric takes the moisture away from your skin, allowing faster evaporation.  

 Lycra vs Spandex vs Elastane

Spandex, lycra and elastane are interchangable words for what is essentially the same synthetic fiber, whose chemical construction is actually "polyether-polyurea copolymer" (try saying that three times fast!) Lycra is a brand name (owned by Invista, previously the well-known name DuPont) as well as being a common term for this stretchy fibre. 

Spandex fiber is created through a complicated process involving chemical reactions, polymer compounds, a spinning cell and heat treatment - okay, maybe I've oversimplified that a bit. There's a wiki here if you really want to read about how it is produced. The end result is a spool of fine stretchy fibre which can be combined with other fibres - such as cotton, bamboo or polyester - and knitted or woven into the fabrics we know and love. 

Fabric Weight

 "GSM" stands for 'grams per square metre. Basically, the higher the GSM, the heavier the fabric! Our Supplex is 280gsm and is ideal for tights; whereas Sorbtek, at 250-260gsm, is marginally lighter but more compressive. Really, we sewists tend to go by 'feel' and can usually tell if a fabric would be better for tights or tops. Want a sample? Contact me at hello@sewactivefabrics.com.au and I'll see what I can do!

Circular Knit

When I first heard this term I was reminded of a holiday in Peru several years ago, and the young men I met at a textile community, who knitted their own hats in the round.

Of course, when talking about mass production, it's a different story.

Circular knits are made on a circular machine and usually cut to create a flat fabric. These types of knitting machines are also responsible for all the ‘seamless’ garments we see such as pantyhose, tights, and underwear.

 Fabric Weight

"GSM" stands for “grams per square metre”. Basically, the higher the GSM, the heavier the fabric! Our Supplex is 280gsm and is ideal for tights; whereas Sorbtek, at 250-260gsm, is marginally lighter but more compressive, and also good for tights. Really, we sewists tend to go by 'feel' and can usually tell if a fabric would be better for tights or tops. Want a sample? Contact me at hello@sewactivefabrics.com.au and I'll see what I can do!

Stretch factor

There can be a lot of variation in how “stretchy” a fabric is. Good patterns will give an indication of how much stretch your fabric should ideally have, such as 50% or 70%. The stretchier your fabric, the looser your fit will be. You can measure your stretch by pulling a fold of fabric along a ruler and noting how far it will go. If it stretches from 10cm to 15cm, it has 50% stretch. You can find some great tutorials for working this out here and here, and a nifty free stretch gauge here

You also want to consider recovery - how well the fabric springs back after stretching out. We know that even the best tights will start to sag after a long period of hard wear (and hey, doesn't that just give us a good reason to make a new pair?) But - the better the fabric recovery, the longer the lifespan of the garment will be. When you are checking your stretch percentage, also note if the fabric quickly returns to it's original size and shape. Most natural fabrics don't have great recovery by themselves - but if our friends Spandex and Lycra are in the mix, even in a small percentage, the recovery will be much better. 

Want more? Come back soon for further explorations into the world of sewing and activewear, or sign up to the newsletter to find out about new products, patterns and offers. 


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