PRE WASHING | How to Prewash Fabric

I must admit pre washing fabric is not one of my favorite tasks, but when you are sewing or purchasing clothing, it is a must-do task. Most fabrics will shrink slightly when washed and some will even shrink considerably. Knits, in particular, are prone to shrinking. How would you feel if the dress you spent hours sewing ended up 2 sizes too small after one wash? With a little care and a few simple steps, you can learn how to pre wash fabric.

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Pre Washing

Pre Washing – Why & How to Pre wash Fabric

Why do Pre Washing?

Without pre washing fabric, you might end up with a garment that

  • Shrinks to a smaller size
  • Seams or hems that pucker or twist after washing
  • Color that bleeds into other fabrics or patterns that run

Another important reason for pre washing is to remove finishing chemicals.

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Pre Washing

Many fabrics are finished with starch and chemicals to make it look crisp and nice when on the bolt. These chemicals may cause skin sensitivities and should always be washed out before making children’s and baby clothing.

And yes, it does often feel like an annoying extra step that you will question yourself doing. But prewashing saves time in the long run and stops you from wasting hours sewing garments that won’t look good after the first wash.

How to Do Pre Washing

Pre washing It depends on what kind of fabric you are going to be sewing.

Cotton, linen, denim, rayon, silk and natural fibers should always be prewashed as they are likely to shrink. Synthetic fabrics, while they will not shrink, should still be prewashed to check for color bleeding.

My rule is always to pre wash anything red. No matter the fabric supplier, I always find that red is the most likely color to bleed. Red and white spots often become pink spots so need to be tested.

Always check the bolt of fabric for washing instructions at the time of purchase. I have to admit, though that I do forget to check the label most of the time, so need to use some common sense depending on the fabric composition and the final use of the project.

The Pre Washing Fabric Rule

As a general rule, prewashing the fabric in the same method that you will be using for the finished garment.

So if you are planning on machine washing the finished dress or pants, then machine wash the fabric before you start.

If your final item will be hand wash only, then hand wash the fabric for pre washing.

Here are some rules that will help you decide on prewashing.

  • Cotton – Warm machine wash when pre washing cotton fabric
  • Silk – Handwash in warm water carefully or dry clean
  • Linen – Cool machine wash or handwash
  • Polyester – Cool machine wash
  • Rayon – Cool machine wash
  • Spandex/Lycra – Cold hand wash only

Do You Use Detergent When Pre Washing Fabric?

Yes you should use the same detergent you will use to wash the finished item. In most cases this will be a mild detergent suitable for your fabric type.

Drying after Pre Washing

Air dry after pre washing fabric can be done by hanging it in the shad so it doesn’t fade.

I would not recommend throwing your fabric in the dryer after pre washing. Dryers tend to over-shrink due to the heat. If you have spent hours sewing something with love, you probably won’t be throwing it in the dryer when you wash it anyway.

If you just must use a dryer on the finished garment, then throw your fabric in but do so at your own risk.

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Air Dry the Fabric

Keep some white scraps of fabric handy and throw some in when pre washing. That way, you can easily see if any of the color transfers onto other fabrics. This is especially important if you are going to be color-blocking your designs.

Further reading: How to Test for Colorfastness.

Preventing Fraying in Pre Washing Fabric

It is a good idea to serger or zig-zag the edges of the fabric before washing, as some fabrics fray badly on the edges during the wash.

If you are using a zig-zag, do a wide stitch of length 4 and width 6. A 3 step zig-zag may eliminate any bunching up of a regular zig-zag on fine fabrics.

Further Reading

After Pre Washing

After you have finished pre washing your fabric might look a little sad and crumpled. Give it a gentle press using a water spray and it will look good as new!

Trim any annoying excess fraying and you are ready to start cutting the fabric for sewing.

How to Test Fabric for Shrinkage

If you are worried about what your fabric will look like after pre-washing you can just test a little scrap instead of the entire piece.

This method is often used in commercial production as it is impractical to wash hundreds of meters of fabric at once.

Try this professional technique to test for bleeding and shrinkage.

  • Cut a square 4 x 4 inches (10x10cm). Wash it using your chosen method (machine or hand wash), putting it in with a scrap of white fabric to test the color dyes.
  • After you have washed it, then flatten and remeasure the square and check for bleeding.

The dye transfer will be obvious. A white scrap of fabric should still be white.

If, after pre washing it measures:

  • 4 x 4 inches (10x10cm) – there is no shrinkage
  • 6 x 3.6 inches (9 x 9cm) – there is 10% shrinkage
  • 3 x 3 inches (7.5 x 7.5cm) – there is 25% shrinkage

If there is 10-25% shrinkage, you would then need to go back and wash the entire amount or alternatively put labels on the clothing advising of shrinkage. For no shrinkage, I normally wouldn’t wash the full amount of fabric.

For really large productions, you might use this testing method for a yard (or meter) instead of a small scrap. It just depends on the consequences of shrinkage and how much fabric you can sacrifice for testing.

Pre Washing – Inc Conclusion

So now you can make a great decision about pre washing and save yourself from frustration later on.

Do you prewash fabric before sewing? Comment below.

I shall cast the first comment – ​​My answer is sometimes. As a general rule, I do it for knits and don’t for quilting fabrics if I am using a quality brand that I know doesn’t shrink. For clothing, I do if it is a bright color that is likely purchased to bleed. And I always do pre washing on red articles.

See also how to test your fabric for colorfastness.

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