One of the first rules in sewing is to pre-wash your fabric before you cut it out, so that any fabric shrinkage is taken care of before the garment is made. Who wants to spend hours sewing a new garment, wear it once, then find out after the first wash that it has shrunk beyond wearable? I think we all live in fear of that!
So we diligently follow the rule – we pre-wash our fabric as we are told to do, so our precious hand made garments remain wearable past the first wash. But is pre-washing always the right strategy? Yes and No. Read on – and I’ll let you decide!
Some fabrics are known shrinkers – like cotton and viscose, but it might surprise you to know that many modern fabrics shrink a negligible amount. There are disadvantages to pre-washing, and sometimes they outweigh the advantages. I personally prefer not to pre-wash unless I have to, but I believe it is important for sewers to know the advantages and disadvantages of pre-washing so they can make their own judgement call.
The first disadvantage is pretty obvious – time and inconvenience. To be honest most of us sewing at home are quite happy to spend the time and forgo the inconvenience of pre-washing (not to mention drying, and ironing!) to ensure our garments don’t shrink. I mention this point mainly because in the garment industry pre-laundering is a major inconvenience and time cost – imagine having to wash several bolts of fabric before going into production! It is simply not practical, so the industry has developed other ways which I will mention later.
The second major disadvantage of prewashing is the loss of finish. New fabric has undergone finishing and pressing which makes it look nice and polished. You have probably noticed how washing disturbs this finish and your fabric softens a bit and doesn’t look so new anymore:
This is going to happen anyway with your finished garment, but fabric finishing actually makes the fabric easier to handle when laying up, folding, cutting and sewing. I really notice the difference during handling, so it seems a shame to remove it!
Distortion is another disadvantage of prewashing. In the textile industry final pressing occurs with the fabric tensioned out flat and squared. Compare this to running a hand iron over a large piece of fabric, with irregular steam and pressure, with most of the fabric hanging off an ironing board – distortion of the grain is inevitable. Crepe weaves are especially susceptible to this, when washed they ‘crepe up’ and are flattened again when pressed. Uneven pressing will lead to uneven width and length of the piece, and the grains are no longer straight and perpendicular.
Not only would the seams, hemlines and fit be crooked, but a wiggly grain makes sewing more difficult! Cutting the fabric accurately and on-grain is far more important to me than experiencing slight shrinkage after the garment is complete.
As you can see there are some disadvantages to prewashing. So – what should you do?
I don’t suggest that you abandon prewashing fabrics altogether, but maybe you can check to see if it is really necessary. This is essentially what we do in the garment industry. Although it is quite different to the home sewing industry, there are a lot of things we can take from it. One is that we always test fabrics for shrinkage. If a fabric shrinks too much we either:
- Source a better less-shrinking option.
- Declare the shrinkage factor to the customer. In a loose fitting garment (like an oversized shirt) shrinkage may be imperceptible. If the garment is close fitting (like a fitted shirt) shrinkage may noticeably change the fit and needs to be acknowledged at retail level – like labelling with 5% shrinkage after washing.
- Enlarge the pattern according to the fabric shrinkage specifications, then wash/press the garment after making to return it to the correct size. This involves a lot of testing for accuracy.
- Specify drycleaning only (which is not immune to shrinkage either.)
Not many of these options are great for the home sewer. Instead I suggest you test your fabric for shrinkage to find out if it is necessary to pre-wash in the first place. Here’s what I do for my fabrics:
- Make a test square pattern in card – 20 x 20 cm, with a lengthwise grain arrow. A bigger square will give a more accurate the result, but I’ve found 20 cm to be a workable size. 10 x 10 cm is too small for accurate results.
- Cut out this square with a rough 1″ allowance. If you think it is going to fray horrendously in the wash, allow a bit more and overlock the edges. Cut off any selvedge. Notch either end of the grainline so you can easily recognise the warp direction once washed.
- Wash and dry the swatch according to the fabric instructions. You could wash it more aggressively if there is a risk that could happen to the garment in real life.
- Measure the swatch down the middle. Measure warp and weft directions to assess the different shrinkage in length and width, and measure pre and post pressing if you want to see how this changes things too.
- Calculate % shrinkage = pre-wash cm – post-wash cm/pre-wash cm x 100
- As you can see I’ve written this formula on my 20cm square because I can never remember it off-hand!
- Example: my 20cm square post-wash measures 18.6cm in lengthwise grain and 19.1cm in crossgrain:
- % shrinkage in lengthwise grain = 20-18.6/20×100, =1.4/20×100, = 0.07×100 =7%
- % shrinkage in crossgrain = 20-19.1/20×100, = 0.9/20×100 = 0.045×100 = 4.5%
- Hate maths? For a 20cm square, 1cm shrinkage = 5%, 0.5cm shrinkage = 2.5%. Easy.
- Some fabrics grow! You can use the same formula but will end up with a negative value.
Now you know the % shrinkage of your fabric, but what does that mean in practice? Imagine a pencil skirt. If your hips measure 100cm, and your fabric shrinks 5% on the crossgrain, it would end up fitting a 95cm hip – that is exactly one garment size smaller! Obviously in this case you would need to prewash your fabric.
This fabric is pretty bad with values of 4.5 to 7.5% for shrinkage, and I would reject it if I was manufacturing garments – maybe that is why I discovered it at a designer garage sale! 2.5% is considered within acceptable limits in the garment industry, and in reality most consumers would not notice this amount of shrinkage unless the garment is very fitted. I often make garments for myself knowing that 2-3% shrinkage will occur after washing, but only if there is slight ease to do so.
Lengthwise shrinkage usually affects the length of a garment, so you might prefer to allow for it when cutting rather than prewashing. For example if the lengthwise shrinkage is 2.5% and your skirt is meant to be 50cm long, you’ll need to add 1.25cm.
Another factor to consider is that lengthwise shrinkage might cause things like that zip on your bomber jacket to become wavy. To prevent shrinkage inconsistencies like this I recommend blockfusing all the way.
Once you start measuring the shrinkage of your fabrics, you might be surprised to find out that many fabrics don’t shrink as much as you think. With time you will learn which fibres and weaves do, and which don’t. Some fabrics will always shrink, but armed with the facts you can now weigh up the pros and cons of pre-washing versus the expected shrinkage of your fabric. Knowledge is key.
Are you a diligent pre-washer, or do you only pre-wash when you remember?! Or do you already test wash your fabrics? I always throw viscose into the wash first!