Originally Posted by bearisgray
Some commercial/ready-made bias tapes and trims also shrink.
I was surprised to learn that a cotton/poly bias tape would shrink - but that would explain the "cupping" that occurs after something like a bib is washed that has been bound with bias tape.
One of the first things my Home Ec teacher, back in the early 80's taught us was to wash all bias tape and trims in boiling hot water (leave on the card) and let it dry to pre-shrink it. She is also the one that taught us to pre-wash all our fabric before we made our clothing from it....dry clean what can't be washed.