Imagine if you made a beautiful red and white spotted dress with a white ruffle and the red ran all over the ruffle after the first wash. Disaster! Testing whether for color fastness before sewing clothing is especially important as it will be washed over and over. If would be awful if all your hard work sewing was ruined in the first wash.
Ideally, you should always pre-wash your fabrics. Not just to test for their color fastness but also to pre-shrink. If pre-washing is not possible, here is how you can still check for colorfastness. (read how to prewash fabric for shrinkage)
How to Test for Color Fastness
Step 1: Cut small pieces of your fabric and sew them onto a piece of white fabric roughly double in size. Make sure your white fabric is cotton. Polyester doesn’t absorb dye so you won’t get accurate results.
Step 2: Fold the white fabric in half so the colored fabrics are sandwiched in the middle. Wet the fabrics thoroughly. Leave it for half an hour still folded up.
Step 3: Check whether the white fabric has any dye transferred on to it.
What to do if your fabric is not Colorfast
If the colored fabric is running, then you could try washing it in a salt wash to set the dyes better. However, if you still find the color is bleeding even after washing the fabric, you might just be better using it for another project without contrasting colors.
Do you test your fabrics before washing? Comment below.