All the fabric for your project must be washed separately to ensure that excess dye is removed. You do not need a detergent but the water needs to be hot. Keep rinsing until the water runs clear, which may take several rinses. If you wish to use the washing machine and have no means of collecting the waste water to check for dye, place a piece of white cloth in the machine together with the fabric. If the dye bleeds, it will do so into the white cloth. Repeat the process until no more dye runs. If dye continues to run after repeated washes, you may feel that you have to abandon this fabric. It is not advisable to try setting the dye with salt or vinegar, as it will only set it until the next wash and if you intend to wash your quilt, the color will run throughout the quilt.
After washing, partially dry, then iron the fabric while it is still damp to replace its original crispness. Press with the selvages together just as it came off the bolt.