Fabric shrinkage is a topic that affects all quilters at some stage and is best brought to your attention early on in your quilting journey so that you can make fabric choices that are best for you. Shrinkage of your fabric is not always a bad thing, in fact sometimes it gives you the exact look you were after.
Most quilters control fabric shrinkage by pre-washing their fabrics. While this appears a good idea there are a few things to think about first.
There are several types of shrinkage that occur with cotton fabrics. Some processes are done in the manufacturing of cotton to control shrinkage. Others occur with the end user washing and/or drying the fabrics. The most common cause of shrinkage is the temperature in the tumble dryer. Removing the fabric while it is still slightly damp helps reduce this. Or you could dry the fabric on the line but this can cause other problems with colour migration and fading.
Shrink tests have been done with cotton fabrics and shown that good quality fabrics shrink less, around 2% both in length and width. Poor quality fabrics when tested shrank up to 6% in length and width.
Another factor to consider is that fabrics are stabilized when stitched together in a quilt, so they shrink less than when left in a whole piece.
Whether you prewash your fabric to control its shrinkage or not is a personal choice. Remember to consider all the implications of your choice. Also the manufacturing processes of 100% cotton fabric for quilting will only improve with time.
My personal choice is to not pre-wash my fabrics. I used to pre-wash them but hated all the wrinkling and ironing that was required as a result, not to mention all the frayed edges that caused havoc when trying to untangle the fabric.
The other thing I noticed was that the fabric was a lot softer after washing which made it less stable when being made into quilts. Sure I could add spray starch through out the process but why when using unwashed fabric worked perfectly.
I have not any problems making quilts with non-pre-washed fabrics. In fact I have made quilts with a mix of washed & non-washed fabrics and also had no problems. You need to choose the right choice for yourself and then dismiss all the naysayers to your choice. That's what I do and will continue to do.