Washing applique blocks is not always the next thing on your mind when you have finished sewing them or at least it's not on mine! I'd much rather be sewing them together into a quilt top!!
Washing your blocks not only removes all the added hand dirt from working with them but also any residual glue, fabric pencil markings or spray starch if you have used these. If your blocks are made using lighter colored fabrics then this is probably a very beneficial technique to learn.
The correct washing method to use is by hand. The video below shows the entire process. Sharon uses a product called Synthrapol, hot water and time (at least 2 hours, but preferably over night).
After washing the block it is important to dry the quilt correctly. To do this you need a flat surface, clean iron, cotton batting (not a towel as the fibers will leave crease marks on your block) and several cotton pressing cloths.
1. Mix hot water & Synthrapol - a mild soap used to prevent dyes bleeding, remove fingerprints, dirt, oil etc
2. Place applique block in water and gently ensure all of the block is wet
3. Soak & Wait!!!! 2 hours minimum, overnight preferred
4. Rinse in cold water 2 to 3 times
5. Gently wring to remove excess water
6. Press to dry, from the wrong side using cotton batting, several pressing cloths and a clean iron