I've been quilting for 30+ years and have used everything from cotton blends & old clothes to the nice cottons we now can get. I started stashing batiks after a trip to a Hawaian quilt shop where I learned a lot more about how they are made. Many times the paint has built up as the layers are added which can make them feel heavy or scratchy and bleed when washed. Also, if they are triple dyed (my favorite) the lightest color is added on first, then release (wax) is put on where the next color is not wanted. This can happen several times allowing each color to show through. Of course, if you've ever done any watercolor painting (not on fabric :), you know how washes are created by putting paint on a wet surface so it pools & blends. Then a sprinkle of salt for little dots of more intense color here and there.
It's quite a process -- and does add a density to the fabric. So, the first lesson is to wash 3 times as someone noted in a previous post, and make sure the rinse comes out clear before you stop. Go ahead and dry this fabric -- it has been washed and dried many times while it's on the stretcher and doesn't seem to fray much at all. I've also noted that the grain is straighter so there is less fraying when you work with anything on the bias.
So, in the middle of my closet of frabic is a shelf of loved batiks. My first finished project with them was a purse done in strips. Loads of fun playing with the colors. Hope you try them.