I am a manic pre-washer...but that is of no use to you right now! I would wash the back as you know it's content and it may/may not shrink. If you have used remnants for the front, there is a good chance if they are not cotton, they won't shrink anyway...but if you washed...they would probably fray and become a tangled mess. So, be brave, leave the front as is, wash and press the back and then have fun quilting it. It will be a learning experience and I reckon it will turn out well in the end....and don't forget...WE LOVE PICS! Happy quilting.