Reminder to Self: When pressing the colored blackwork ornaments, do NOT use the steam setting.
That's right. I inadvertently used the steam setting on a colored ornament, and the color ran. I ended up with smudges of red and blue all over it.
There are a couple of solutions; number one being "don't use the steam setting." However, the instant solution is not always the best solution; this does nothing for the possibility of your work getting wet in the future.
The other solution, the one I chose, was to give the design a quick spritz of hair spray. No need to shellac with a heavy coat, just a couple of light sweeps does what you need it to do, and keeps the fabric pliable.
Maria suggested I paint a coat of white glue over the fabric. I've used this method for patches and for framing pieces in a hoop, and yes, it's waterproof. It does, however, stiffen the fabric. I mix water into to the glue (I use Alene's Ok-to-wash-it fabric glue), creating a wash that I can then daub or paint onto the finished work. Here's a link to my tutorial. It's certainly worth a try, depending on the way you plan to finish your piece.
Hope this helps. Stitch happy!