Why you should always pre-wash your fabric

This is the inside of a hat I made for Miss 8 recently.  Her school swimming carnival was the other week and her team is red, so she wore it inside-out [team spirit].  The floral fabric was pre-washed, as I do with all my fabric when I first purchase it.  The red spot fabric I didn't pre-wash, as I used it to make the strawberry bags I made as Christmas gifts late last year.

Of course the day of the swimming carnival it rained.  And this photo is evidence of why you should ALWAYS pre-wash all the fabric that enters your sewing room:

 Unfortunately the photo doesn't do the pink mottled flowers justice.  I know it's annoying to pre-wash fabric before you use it, but believe me, it is worth it.