While washing batting before a quilt is made is not always recommended or required, a good first wash can reduce the minute shrinkage that can occur. Some quilters only prefer to leave the batting laid out to reduce wrinkles, and some fluff it briefly in the dryer in favor of washing before basting a quilt. However, you can wash cotton batting before using it if you don't desire the antiqued look you can sometimes get by waiting for the quilt to be finished and then washing it.
Fill your tub with warm water roughly three to four inches deep. This may need to be slightly deeper if you are working on a king size quilt. Add detergent and mix in evenly throughout the water.
Open your batting and unfold it completely. Add the unfolded batting to the tub; keep it as evenly spaced as possible. An accordion shape, or fan fold, can get the entire width of the batting into the tub fairly evenly in most situations.
Let the batting soak for 20 minutes. Do not agitate or pull at the batting, or it may create areas of weakness or tear. Simply press down on the batting and gently move it as you need to in order for all of the batting to be able to soak.
Drain the tub and rinse the batting two to three times. Refill the tub and gently rinse the batting, moving it back and forth carefully. Drain the tub again; repeat at least once more. Some darker or yellow batting materials will release a bit of coloring. If this is the case, rinse until the water runs clear. Once complete, drain the tub again.
Squeeze the batting to let excess water run down the drain. Roll the batting in a large towel and squeeze to get as much water as possible out of the batting before moving on.
Dry the batting by laying it flat on a large sheet either outside or in a large room. If you have a dryer available with a low setting, you can also let the batting dry on the cool or warm setting. When the batting is dry, you are ready to baste the quilt together.
You can follow these same steps when washing quilts, but only wash quilts you are certain will not run or bleed their colors. Only wash an antique quilt as a last resort.
If you do end up with a rip in your batting, use a left over piece of the same kind of batting. Hand baste a patch over the rip. Once the quilt is created, you will never notice the slight change in depth, and the quilt should hold up well even with the secret flaw inside it.