Cotton muslin most often comes in white. If the muslin has sat for a long time and was improperly stored, it might eventually turn yellow. You can restore the cotton muslin to bright white with bleach. Use another process if you are concerned about using a toxic chemical in your home. Bleach produces noxious fumes that can be hazardous to your health and can irritate your skin and eyes. Use an alternative solution that is natural and non-toxic.
Fill the washing machine with cold water.
Pour detergent into the water according to the detergent manufacturer's instructions.
Close the lid and let the washing machine run for five minutes.
Pour 3/4 cup liquid chlorine bleach in the water for a normal load. Use 1¼ cups for extra large load.
Put the cotton muslin in the washing machine.
Close the lid and let the washing machine run. Dry the muslin as normal.
Fill a washing machine with cold water. Add washing powder. Add ½ cup baking soda to the water and let the cycle run for a few minutes until the baking soda and washing powder are fully dissolved.
Put the cotton muslin in and let it soak overnight.
Close the lid and let the cycle run as normal.
Hang the muslin to dry in the direct sunlight. The sun will continue to whiten the fabric.