If you go to McKenna Ryan's website (pineneedles.com) there is a write up about how she does this technique (
http://www.pineneedles.com/SearchResults.asp?Cat=1877). She uses clear thread in the top and regular cotton thread in the bottom. I agree with sewingsuz, I would (and have) use this technique on wall hangings but I would be very tentative about using on a bed quilt or anyone that would be washed a lot.