This is a great question. A few days ago I bought a loose piece of batting at an estate sale -- that is, not in a package. It has an unfamiliar feel to it, and I can't identify the brand, but I think it is cotton. I cut off a little corner and hand washed it just to make sure it didn't fall apart. It was ok.
So, I am ready to wash it and see what happens. If a batting shrinks, I want it to happen before I use it.
Also, I have been told that although fabrics are treated with pesticides for their trip across the ocean to us, batting does not have pesticides added in the manufacturing. I am not sure if that is true or not, but I think I will feel more comfortable using a clean piece of batting that I found unpackaged at an estate sale.
I paid $1.50 for this 2 yard piece of batting, so I am willing to put a little effort into it.
Dayle