I finished up the ripple quilt the weekend before last. I had marked the circles for quilting using a compass and a soft graphite pencil. As I went along most of the marks came out (or smudged evenly), so I wasn't too worried about washing out the last bits after binding the quilt. But just to be sure I applied some diluted Tide detergent to the most obvious marks, then headed off to the laundromat to wash this and the two other quilts I finished in August (!) in a large front-load machine.
Well, I got distracted and ran an errand or two before the laundromat, letting the detergent sit on the fabric for a little over an hour. Didn't seem like a big deal. The blankets came out of the washer looking fine, with no trace of pencil. But when it came out of the dryer there were big discolored bloches -- like dingy age stains -- everywhere I had applied detergent. Ack! And a subsequent rewashing and air drying did nothing to get rid of the stains. Ack!
After a lot of interweb consulting and Twitter hand-holding, I've managed to make things right. I didn't try all the suggestions (I would have if I had to!), but the thing that worked was distilled white vinegar. I threw the blanket in the tub, doused the whole thing with a gallon of vinegar, and let it sit for an hour. Then I filled the tub with cold water, agitated a bit, and let it sit for another hour. Finally, I drained the tub, sent the quilt through another wash cycle, and voilà, the stains are gone.
Here's a photo of the damp quilt hanging to dry. The view is from the back. The khaki strip with the orange and white circle are on the back (the side facing us) and the front, visible through the backing and batting, is an arrangement of drunkard's path blocks pieced from a Kaufman Kona charm pack and various off-white solids. Hope to have more photos of the quilt in more presentable condition soon!