I have learned another lesson about yarn. I know that you are supposed to use the same dye lot on a yarn project. I am using two dye lots because we threw half the yarn away and I had to buy more a year later from the same store. I thought dye lot was because of color. I decided that these two lots were very close in color and I thought I was home free. As I told the yarn store owner, "I'm going to let it go", meaning I'm not going to worry. The color is almost exact. However, in knitting the last four inches of the back of the sweater, I have discovered that the bulk, or the weight of the yarn is different. The new dye lot is a bit finer...and although I don't think anyone will notice, to me, working with the yarn through my fingers, there is a big difference.
I am going to forge ahead. It is still a pretty yarn, and it is just a sweater for myself. I think it will be fine, though the heavier yarn is more fun to work with, the lighter weight might even make a prettier sweater. Look on the bright side.
Have a great day.