I know how you feel.  You’re excited, you have an exciting new pattern and gorgeous new fabric and you just want to get the scissors into it all, and launch at the sewing machine, and glory in the noise and the pins and the thread, and listen to your favourite CD  or audio book while everybody else is out of the way and/or asleep, and just sew.

Whether you’re a new or a seasoned sewer, this is your special time when you can really breathe freely, loosen up your shoulders and relax into creativity, chaos and construction.  You really don’t want to delay it for the sake of Extra Laundry.

What’s all this fuss over pre-washing anyway?  Do I have to?

Whether or not you need to pre-wash your fabric basically depends on whether you’re sewing something that will ever be washed, and whether it’s important that it stays its intended size.

If you’re sewing a quilt to be hung on the wall or dolls clothes that are probably never going to see the inside of a washing machine, then no, I probably wouldn’t bother pre-washing either.  And neither would I worry about pre-washing fabric destined to become a peg bag or laundry bag, because who would actually notice or care if they shrunk?

But if you intend that the finished item will require washing, and if you need it to stay the same size after washing, then I’m afraid you are probably going to need to pre-wash, yes.

Almost all fabrics need to be pre-washed in the way that you intend to wash the finished item.  This definitely includes tumble drying (if you tumble) and ironing, as the heat of these processes will shrink the fibres further.  Plus, ironing the fabric will get it nice and wrinkle-free ready for the pattern cutting.

Some people also pre-treat dry-clean only fabrics at the dry-cleaners, although I can’t comment on this as I’ve never sewn with dry-clean only fabrics, and haven’t been to the dry-cleaners since I picked up my wedding dress five years ago.

There are some fabrics which don’t require pre-treating; 100% polyester fabrics such as polar fleece and minky don’t need pre-washing, and neither do faux leather or vinyl.  While I’m far from a fabric purist and am as much of a fan of the low cost, easy-care, minimal ironing qualities of poly cotton as the next person, it would be a pretty dreary wardrobe not to have totally gorgeous cottons, rayons and wool blends included within it.  And a fairly niche wardrobe to be solely concerned with faux leather or vinyl.

How much will it shrink?

The amount of shrinkage a fabric goes through depends on its fibre content and the process that was used to produce the fabric.

Generally, fabrics with a natural fibre content such as cotton tend to shrink more than synthetics.  Woven cotton will shrink by around 2%, although some might shrink considerably more than this.  The shrinking can be reduced by careful laundry practices (a cool hand wash and a cool iron), and will be increased by a hot wash, tumble dry and a hot iron.

The shrinking doesn’t happen evenly across all directions of the fabric either.  Woven fabrics shrink more in the warp (length)  than the weft (width), so sleeve length, shirt length and collar are where you can expect to the the greatest amount of shrinkage.  Happily there isn’t usually so much shrinkage around the girth of an item.  (Except at Christmas, strangely).

Why does fabric shrink?

There’s some science at work here.  Do you remember learning about material memory in your Crafts & Design classes at school?  Well, that’s pretty much what’s going on.  When fibres go through the processes of being spun into thread and woven into fabric, they are stretched and put under tension.    Then, when you have the fabric at home and wash it for the first time, the heat and agitation of the laundry processes loosens the weave and and allows it to ease back a bit.  And voila, there’s your shrinkage.

shrinkage in high twist yarn

threads shrink along their length, so a ‘high twist’ yarn directs the thread’s ‘length’ around its girth. This squishes the yarn in as though it’s bound in a Victorian corset when shrinkage occurs, resulting in a skinnier (denser) yarn with less loss of length.

How the yarn was woven has an impact on the level of shrinkage.  A “high twist” means that the threads are more helical, so when the fibres shrink the entire yarn doesn’t shrink as much because the shrinkage is happening more around the yarn, rather than along its length.

Cover factor is another factor which affects how much or how little a fabric will shrink.  It’s a measure of how tightly the yarns are woven; the tighter the weave, the less the fibres are allowed to shrink because the shrinkage puts tension on other threads that are also trying to shrink.  Eventually the cloth reaches a state of near equilibrium where the threads are still stretched but can’t shrink any more due to the natural tension remaining in the weave.

Felting can be another factor in how much a fabric will shrink.  Certain fibres, like wool or fur, will matt together under heat, moisture and agitation, such as in the washing machine.  This matting pulls the fibres tightly together and creates a very thick, dense fabric, which is also shorter (and narrower) than it was originally.  Woven or knit woolen fabrics can be felted to create amazing, dense fabrics.  Or a really expensive dog jumper if you accidentally stuffed your best mohair sweater in with the bedding on a hot cycle with a high spin.

What should I do?

Well, you could size to allow for shrinkage – increase sleeve and body length by a few centimetres to allow it to shrink when you wear and wash it.  If you’re sewing for children, though, (which I assume you might be if you’re reading this blog) you must also accept that kids grow.  Either that means you will accept that they will outgrow your creations sooner or later, so why stress if it’s a bit sooner due to shrink, or you give them plenty of turn-ups at their trouser legs and sleeves to accommodate the shrink.  This is probably an excellent approach to sewing for kids anyway, clever you for thinking of it.

prewashed fabrics hanging on the line

The view from our garden on stash pre-wash day

Or, you could pre-wash your fabric before you start.

Now – even if you do choose to pre-wash, you should be warned that pre-washing won’t make your clothing totally shrink-proof.

Shrinkage happens over time, not all at once.  Usually fabrics will shrink most the first time they’re washed, but they can still be expected to shrink more over the life of the garment.  The first wash might get about half of the shrink out of the fabric, the second wash another quarter, the third wash another eighth, and so on.  But getting half the shrink out of the way before you start is pretty good going, in my book.

I don’t mind pre-washing, to be honest.  I enjoy the anticipation, I really like to see the fabric hanging on the line so I can appreciate its colours and patterns in daylight, and I don’t even mind ironing it.  Ironing never seems a chore if it’s linked to sewing.

Also, I’ll often pre-wash a few fabrics from my stash at the same time, so I know that when the mood takes me, when that fabric is the single best fabric for a new project that I absolutely must sew right now, this very instant, I know that it’s good to go and that I can cut straight into it without a moment’s further hesitation.  Provided my pattern has already been traced, of course.