I would think that 77% bamboo is too much for a successful sock yarn. You could cut the proportions and spin a small amount of the bamboo with additional superwash.
I just passed this up, because my mind immediately went to thinking "I don't have fiber to spin, I already have spun yarn". Now, in my defense, I am use to buying yarn that if it is of multiple fibers, they are blended and then spun as yarn . . . no separation is possible. But as I walked to work in the rain today, the rain is a nice place to think, anyways, I realized that I didn't think this yarn was blended and maybe I could take her advice and split them up.
So, when I got home, I found that the bamboo and the merino are separate singles. Yippee! So, here is my work so far:
I have the skein on my spindle because I am going to deconstruct it. Here it is with the spin/plying to hold the singles together, undone. I am going to take this and separate approximately half to two-thirds of the bamboo out and re-ply it. The merino has two singles that are about as thick as 5 or so of the bamboo singles. There are 18 bamboo singles in the yarn, I am thinking of cutting it down to 5-7 singles of bamboo.
I will most likely end up using the rest of the bamboo singles in some future spinning venture. So thank you very much to Kim, as I think you helped me solve my problem . . . even if it took me a little while to get there! :)
I think these will end up making some perfect little socks for my niece, Justice.