I've done several little hearts with machine applique stitches on small squares. Should the edges be sprayed with something to keep the edges from fraying when washed?

Did you use a fusible to hold your fabrics together before you stitched? What kind of stitch did you use?

If you are using a fusible (like heat and bond lite) and a machine satin stitch, you should not have any fraying when washed. If you are using a blanket stitch and the quilt is washed repeatedly it may fray a tiny bit over time. I do not know of anything to spray on to keep it from fraying. Even fray check (which will make your edges stiff) will wash out eventually.

The idea is to let them fray. Part of the plan with raw edge.

This is a double posting.

I think part of the charm of raw edge applique involves allowing the edges to fray.

Is this a quilt or wall hanging? As some one said, it's part of the raw edge so it's supposed to fray a little. Also if it's raw edge then I don't use anything to secure the edges. If not raw and I'm not a big fan of raw, then I use a heat and bond on the edge. That way I can either satin stitch or applique stitch.

You can also zig zag a narrow braid around the edges, ric rac, or any other decorative item and it will cover the raw edges :D:D:D