Originally Posted by Prism99

In something on the order of 20 years of quilting, I had never run across that batting name. Googled it, but didn't find anything that gave shrinkage on it. I think if you were to switch to a more widely known brand of cotton batting you would be much happier.

Although muslin can shrink a lot on its own, once it's quilted to a batting the shrinkage of the batting takes over. A lot of quilters use unwashed muslin and don't get 18% shrinkage; however, few quilters seem to use thie Arctic Cotton brand of batting and it's easy to see it shrank a lot. Hard to believe you pre-shrank it too!

Edit: In a class I took, Harriet Hargrave passed around a flannel quilt she had made without pre-washing any of the flannel or the batting. It was fine! She had used Hobbs 80/20 batting. I honestly think your problem was caused by the batting.