WHAT IS IT?
Prewashing is basically washing your fabric before you start cutting or sewing. That’s all there is to it!
WHEN DO YOU USE IT?
I recommend always washing your fabric before using it. Doing so eliminates the fabric’s finishing chemicals, which can irritate people with sensitive skin. You’re also reducing the chance that your fabric will shrink the first time the finished garment is washed.
WHY BOTHER PREWASHING?
To avoid shrinkage! There’s nothing worse than seeing your beautifully finished project come out of the wash shrunk. Luckily, you have control of the shrinkage if you wash the fabric before cutting.
To remove sizing and finishing. After fabric is dyed, chemicals are used in the finishing process, including sizing, a substance that adds stiffness and smoothness. It’s nice to wash the chemicals out of the fabric before you start working with it, especially if you have sensitive skin. On the other hand, these finishing chemicals are there to stabilize the fabric and might make it easier to work with, so your fabric might have more drape and softness after washing.
To prevent bleeding. Fabrics like denim or dark fabrics are heavily dyed, and it can take several washes to get out the extra dye. That extra dye can rub off or “bleed” on to other fabrics. Without prewashing, these fabrics can stain your undergarments, your furniture and even your skin! Denim fabrics, dark navy and black fabrics and red fabrics are prone to bleeding and should definitely be prewashed.
To make it clean. If you’re not particular about used fabric, buying fabric from thrift stores and online is a great and eco-friendly way to go. Vintage and pre-loved fabric may smell musty from storage, so give it a wash so it’s fresh to work with.
HOW TO PREWASH YOUR FABRIC
The general rule is to wash your fabric the same way you would wash the finished garment. If you plan to machine wash and dry your finished garment, then do the same to the fabric. That way the fabric won’t shrink or change after the garment is washed.
Another theory is to wash it harder than you’d wash the finished garment. Even if you’re going to handwash your finished garment, there’s a slight chance someone might toss it in the dryer accidentally and shrink it. If you wash and dry the fabric beforehand, then the shrinkage will happen before you sew up your project.
One last thing to consider: Prewashing may change the feel and the drape of your fabric. Crisp fabrics like taffeta or linen may become soft and limp. If you’re unsure, cut a large swatch (8″ × 8″ [20.3cm x 20.3cm]) and wash the swatch separately first, to see how washing will affect the fabric.
Prewashing cotton fabric
- Always prewash cotton fabrics! Cotton will soften up a little after washing, plus it’s the most likely fabric to shrink later.
- For cottons, including denim, consider washing your fabric harder than you normally would. This means hotter temperatures than you might normally use, a more vigorous wash cycle and a hot dryer even if you might hang the garment to dry.
- For heavy cottons or denim, or when making garments where an exact fit is required, prewash your fabric more than once. Have you ever had a pair of pants that kept on shrinking each time they were washed?
- Rayon/viscose is very similar to cotton (both are plant based), so I treat them the same way. Rayon can shrink as much as cotton, and some rayons will shrink more! However, many rayon garments are dry-clean only. You may choose to always dryclean the finished garment. Types of rayon fabric include bamboo, tencel and modal. Look for care instructions on the bolt of fabric and take note for your sewing projects.
Prewashing wool fabric
Most garments made of wool fabric are going to be dry-cleaned and not machine washed. How do you account for shrinkage? Here are some ideas on how to pretreat your wool fabric.
- Steam it. Working from end to end, hover the iron over the fabric and apply steam. Repeat until you’ve covered the entire length of the fabric.
- Get it preshrunk by a dry cleaner. You may be able to ask your local dry cleaner to preshrink your wool yardage. This is costly, but it reduces the chance that your finished wool garment will shrink and become unwearable.
Prewashing silk fabric
Silk fabrics are delicate, so handle with care. Silk can be washed, but it will often change the texture and sheen of the fabric. You can cut and sew it unwashed, knowing that you’ll have to dry-clean the finished garment. If you’d like to be able to wash the finished garment, try handwashing a tiny piece and see how it turns out. Silk may get softer, more wrinkled and less shiny after it’s washed, so you might not like how it looks. Or you might love it, and then you will be able to wash the finished garment.
Prewashing polyester, nylon and synthetic fabrics
- While synthetic fabrics are unlikely to shrink, you might want to prewash polyester and nylon fabrics regardless to remove any chemicals and to freshen them up if they’ve been in storage.
- Polyester dries really quickly, so you won’t have to put it in the dryer very long, if at all. Polyester comes out of the washer just about dry!
Tips + Notes
- To avoid your fabric fraying at the edges in the washing machine, finish the edges before washing. You can trim the cut edges with pinking shears (page link), zigzag across the edges (page link) or run them through the serger (page link).
- Prewash the trims and notions for your project. Check the packaging for notes on whether the trim is preshrunk.
Source : The Sewtionary An A to Z Guide to 101 Sewing Techniques + Definitions
About the Author : Tasia ST. Germaine