Should I Pre shrink and pre wash my fabrics before I sew with them?
The short answer is...Yes do it (most of the times). The long answer is bellow ;)
The main reasons why you should pre wash your fabric:
- To pre shrink
- To wash out dirt and chemicals from the production process
Most fabrics from natural fibers shrink when you wash them. Cotton fabrics often shrink around 5%. But a shrinkage between up to 10% is not uncommon in fabrics made from natural fibers. So if you don't wash your fabric before sewing, and then wash your final garment, your garment you might not fit correctly.
To prevent this you'll need to wash and dry the fabric like you'll wash and dry the final garment. So if you plan on doing a hand wash...give the fabric a hand wash. If you plan on washing it in the machine on 30c then do that.
Some of the shrinkage tends to ease as you wear a garment (like with jeans after washing) but lengthwise shrinkage not so much. So it's worth it to pre wash, if it's a garment that has a fitted style or if the fit and size really matters.
Another important reason is to wash out the dirt / remove chemical sizing / starch treatments / excess dye from the production process. The treatments make it easier to handle the fabric during production and strengthens the yarn for weaving, washing them out will soften your fabric.
When not to pre wash fabric?
If it's an accessory that you wouldn't wash in a washing machine, like if I would sew a zippered pouch or shoulder bag where you would only do spot cleaning.
For fabrics that are dry clean only and garments that are more structured like a woolen, tailored jacket. In those cases I would simply steam the fabric prior to sewing and cutting by hovering the iron above (not on! ) the fabric. The steam helps to pre-shrink the fabric too.
When you pre wash raw indigo denim, creases and fold in the fabric might lead to white lines on your fabric, that's why some don't pre wash denim and use it right away.
100% synthetic fabrics might not need pre washing to prevent shrinkage, but it might still be a good idea so you can work with a clean material.
How to pre wash fabric?
I've already mentioned you should wash and dry your fabric like you want to wash the finished garment, but there is another thing to consider...unfinished fabric frays and you could loose some of your length if you don't treat your raw fabric edges first.
How to prevent your fabric from fraying when you pre wash your fabric?
The selvedge does not fray, but the cut ends do. There are a few options to prevent and reduce fraying:
- Use a serger to finish the fabric edges.
- Use a zig zag stitch on the edge of the fabric.
- Zig zag or serge the cut ends together to create a tube.
- Use pinking shears to reduce fraying. I think this works best for fabrics that have a finer weave that don't easily fray.
- Pre fray your fabric. Pull out the about a cm or 3/8"of the weft thread (that goes from left to right or selvedge to selvedge) this creates an almost decorative frayed edge that prevents further fraying. You'll see this on scarf ends and on linen place mats.
- don't...let it fraaay, let it fraaay, and cut of the fray edge after drying.
To be honest I can only remember doing fray prevention once. I have a silky woven bamboo viscose that is an absolute tangled nightmare if you just throw it in the washing machine. I ended up serging the edges. And for cotton muslin rectangles that I used to print on, I pre frayed the edges to look decorative and prevent further fraying.
A few more tips for pre washing your fabric
- wash a test swatch. If you cut a 10cm or 4" square its easy to measure it after washing. If you finish the edge prior to washing, you can check how much it shrinks and how well it holds up in the wash.
- Unfold your fabric before you put it in the washing machine.
- Don't over crowd the washing machine.
- Wash similar colours together since there might be excess dye in the new fabric that could stain other fabrics.
- bonus points if you immediately iron your pre washed fabric, and catalogue it in your fabric swatch library
That was the long answer. It safe to say that for most garments it's a good idea to pre wash the fabric, but it depends on the project and the type of fabric. If you are unsure ask the shop where you bought the fabric for tips and if in doubt wash a test swatch first.