See this sweater? It is a blend. I bought this to wear, and since it had a really low wool content, I threw it in with a load of laundry, and washed it on "cool". It came out lightly felted, like a merino usually does after a hot wash! Since I could no longer wear it, I was curious to see if it would fully felt, so I through it in with the next hot load. This is the results... the sweater underneath is the same size the gray one started out. My 6 year old couldn't fit into it now.

How much wool content, you ask?
Yep, 30%. Isn't that crazy? This is why I laugh when I see tutorials that say "you must use 100% wool or it will not felt". Granted, this is an unusual result for such a low content, but higher wool content blends (I only sell 70% & higher wool content blends) are pretty predictable felters.
On a completely unrelated note... I found this at the grocery store the other day, and had to try it.
It kinda tastes like an ugly sweater too ;).