I'm sure that I used Elmer's Washable School Glue. I no longer have the bottle, but I recall that it had a blackboard on the label. I added about 25% water and rolled it on with a bottle roller in a random pattern. I usually start by putting the quilt top down first, but luckily, I started with the backing this time, so I hadn't put any glue on my top yet. I've washed it several times and even let it soak for a few hours. Much of it came out, but it's still stiff in places. I think that I'm just going to trim off the unaffected edges of the backing and throw the rest away. Sad, but a lesson learned.
~ C