From a comment by "Kristal" (September 13, 2012 at 4:44 am) on the relevant day's Worsted For Wear comment section:
There's a secret to using Red Heart. Leave it in the skein, but remove the wrapper. Get the whole darned thing damp - all the way through to the core - then wrap it tightly in a plastic bag. Tie or ziploc the bag shut so no air or water escapes, then toss it in the fridge for a few days.So, we start with a partial skein of green Red Heart.
The scratchy fades.
A lot of the scratchy, awful feel is from the sizing chemicals they put on the acrylic. The water and cold breaks these chemicals down, and gets rid of a surprising amount of that nastiness.
Then, fill a bag with water, get the air out, and put it in the fridge:
Now, in the photo on the right, the water appears to have a greenish tint - it doesn't really at this point - it's just refraction, reflection, and other neat tricks. Four days later, however....
Yeah, that water is pretty green. Next, we remove the yarn from the bag, carefully dump the oddly green water, and rinse the yarn.... and then hank it so it can dry. (My lack of tinker-toys is evident; I'd have a knitty-noddy else.)
Now, the test. Is it actually any softer than un-soaked Red Heart?
The answer: NO. In fact, the soaked yarn feels slightly sticky/tacky at this point, but the un-soaked yarn actually feels about the same scratchy-ness. I will continue the experiment later by knitting up one mitten from the soaked yarn and the second from the unsoaked, to see if there's any difference in how it feels as it's worn, but I'm thinking (at this point) that soaking Red Heart doesn't really do much. Possibly they changed the formulation of the yarn or chemicals - but this batch is no softer than it started, and feels slightly worse.
PS, if you're not reading Rachael & Josh Anderson's Worsted For Wear webcomic, you should be!!