I weave with what is regarded as a very good brand of mercerized (pearl) cotton. When I finish a piece, I wash it and rinse it in cold water, but it fades/run/migrates terribly. I just finished a baby blanket using fuchsia, turquoise, purple, and dark green mercerized cotton. When I washed the blanket, I put a white handkerchief in with it. When the cycle was finished, there was so much color bleeding that the handkerchief was almost as deep a fuchsia as the mercerized cotton thread. I realize that colors with red are most likely to migrate, but I’ve had problems with other mercerized cotton colors as well. Is there a way to prevent this loss of color?
I do know what you are talking about. When I first started weaving, I was shocked when another weaver gave a program in which she said: “Handwovens are always improved by washing.” At that time, I loved exactly how everything looked when I wove it, and so I never washed anything.
Eventually, I started teaching, and one time when I was teaching overshot I had a set of placemats with me that were woven in natural 10/2 pearl cotton using a 3/2 pearl cotton weft in the color Garnet. While I was lecturing, they were on the table in the middle of a group of weavers. As I talked, I could suddenly see a sort of pink aura, growing on one end of the placemat. As it got darker and larger (twilight zone!), I reached over and pulled up a corner of the mat. It had been lying on a wet tea bag, which caused color bleeding.
After many years of experience, I have learned the joys and trials of wet-finishing (after all, can you really use placemats you don’t dare wash?). I have found that it is usually the reds that run, especially red violet. I think the issue is over-saturation of the dyes, rather than any issue about their quality. What I’ve done since the tea bag episode is wash all pieces first by hand. I wash and then rinse many times in room-temperature water (and only with the item itself in the water) until the rinse water runs clear (this usually doesn’t take very long). Then, I take the item out of the water, roll it in towels to get rid of as much water as possible, and press the piece with an iron until dry. This stops the color bleeding as it dries. Any remaining dye would run into the adjacent threads if you allowed the piece to dry on its own.
For future care, I machine wash, but again remove it from the washer, roll in towels, and press until dry. I have used that same Garnet weft since and treated the pieces that way with no running of the dyes (but no amount of washing will take out the tea bag aura from my original mat).
Learn more about the process of wet-finishing in this video from expert Laura Fry!