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Most backpacks will indicate machine wash, gentle cycle, in cold water. Depending on the design of your bag, you still may need to hand wash if there are jewels or decals that may be damaged in a washing machine. Do not wash your backpack with other material to avoid any colors bleeding and soaking into your backpack. You may also run your washing machine through an empty wash and rinse cycle to get rid of any detergent residue. Once finished, remove your backpack from the washing machine and laundry bag and set it aside to dry. Keep it away from any direct heat and hang it upside down to allow any water out of pockets and creases. Do not use a dryer as it may damage certain fabrics.
Follow washing instructions. Ensure that the washing machine is clean and clear. Dry your backpack naturally.