Prewashing trims and interfacing

I have some purple colored cotton lace to add to a dress I am making- do I need to prewash this?  If so- how do I keep it from getting all tangled up- would steam ironing it serve the same purpose?
 Also, I am supposed to wash fusible interfacing?  I have pellon featherweight fusible.
Thanks very much!
Jean

I have never prewashed trims or interfacing, although I do prewash flannel if I use it as an interfacing.

I've never washed trims either and have not had any problems. You are not supposed to prewash fusible either.  I don't think there would be a way to do that anyway. If it would shrink, the iron will take care of that.  I hope this helps you out. 

I think I would probably give it a good steaming to shrink it up OR hand wash and then tumble it dry in a lingerie bag. I would be concerned about shrinkage.

If the cotton lace were of any width I would pre shrink it.  To preshrink it I would do it in the sink, plunge it into very warm if not hot water with a good dose of vinegar to set the color. If you have ever had a trim shrink noticeably or have the color run, you would never risk it again. I pre wash all of my cotton fabrics. I made a First Communion dress for my goddaughter that shrank 2 inches when I was finished. I was sick. A dress with over $150 worth of fabric and laces shrinking will do that to you.

Fusible interfacing, I would pre shrink. I am not personally a huge fan of pellon, it does not stay fused in my experience. To pre shrink it you can soak it in the sink and hang to dry. That is how I pre shrink the fusible interfacing I use fusible woven interfacing. Usually a product known as German Interfacing and I am getting ready to order some interfacing from http://sewexciting.blogspot.com/ to try.