All my fabric gets washed, hot water/dryer, before it is added to my stash!
I want to know what's going to happen with it for the long term.
For sparkles, I really want to know, so I am not disappointed after I've done a lot of work.
I've had some where the sparkles virtually all disappeared.
Some minimal disappearance.
One, the sparkles were more of a plastic bead ... no problem in the wash, but if you iron it, they melt.
And some ... never has lost a thing .. it is more like a rainbow metallic melted into the fabric. I had quite a bit of it .. and now wish I had more of it, and could get other colours.