I use Hobbs 80/20 all the time and I machine wash my finished quilts in cold water and I dry them in the dryer and haven't had a problem. I'm not sure what kind of Hobbs you have, so I suggest you make a little sample - about a foot square with the batting in it and put a little quilting on it - and throw it in with your laundry. Measure it before you wash it and after to see if, or how much, it shrinks and how the sample looks after it's been washed. Most likely, it will shrink a little and give a little bit of a wrinkled, old fashioned look, but that might happen even if it is hand washed.