Why I like making two ply yarn

We got a new drum carder, a Fancy Kitty.  It's awesome.  I can finally spin really thin consistent yarn.  I'm trying to make sock yarn, which runs about 14 wraps per inch.  My first try is this blue skein, which measures 11 wraps per inch.  I made two batts, one for each ply.  At over 230 yards, it's the longest single skein I've ever spun. 

My second try is in pink.  Here you can see two batts, each weighing 2 ounces.  One of them is already half spun into a yarn single. 

What I learned:  I like making two ply yarn for several reasons. The great disadvantage to plying is that you have two spin two or more times as much yarn, so you've got to have good reasons to do it.   First, and most importantly, plied yarn stronger than single ply, and since I want to make sock yarn, strength is important.  Second, when you ply two singles of yarn together, they puff up to make wonderfully springy yarn.  To get similarly springy yarn from a single thicker ply requires significantly less twist, which means that the fibers are not very well held together, and agian, the yarn isn't as strong.  I also like doing the plying, which is relatively fast and easy on my spinning wheel, and watching the two colored singles ply together is both mesmerizing and satisfying.  The plying creates sections of high and low contrast in color, which makes knitting the yarn more insteresting.