Why Pre-wash Fabric?
- Preshrinking fabrics removes excess dyes and chemical finishes used in the manufacturing process.
- Most cotton fabrics shrink 2-3% when washed and dried, so if they are not preshrunk, the fabric may pucker at the stitching lines the first time it is washed.
- Some dark or vivid colours need to be checked for colourfastness to determine whether the dye bleeds to light coloured fabrics or colours the water.
How To Pre-wash Fabric
- Use a mild soap to machine wash fabric before you cut it for sewing.
- Do not use soap intended for fine woolens as it may yellow cotton fabrics.
- If the colour bleeds use a colour catcher in the wash, some people also recommend using household vinegar to prevent colour bleeding.
How To Test for Colourfastness
- Fill a glass with warm water and a few drops of mild soap, such as dishwashing liquid.
- Cut a small square of fabric and place in the water. Allow to soak until the water has cooled slightly. Swish fabric.
- Place wet fabric on a sample of light-coloured fabric; blot dry. If dye transfers to the light coloured fabric, repeat the test; if fabric still bleeds, it is probably not colourfast.