The only things I have ever felted were recycled sweaters to make into felt shoes. In that case, you felt the crap out of them-throw them in the washing machine on hot and hot dry them a few times to make it pretty stiff and thick.
Well, I just made my first hat. It is huge and I'd like to felt it down a size or two instead of junking it (it was for my husband and is big on him-he has the largest head in the world so it isn't like it will be useful for someone else). How do you slightly felt something? I don't want it to super shrink or get really stiff so that it would be uncomfortable or too small to be any good. If it felts a little too small I could wear it instead of him and if all else fails we have 2 small boys that could wear it, I just don't want it to be really stiff. Any ideas?
You'll still need to wash it in hot water in a machine, but you'll just have to keep a very close eye on it...like stop the aggitation and take it out about every 2 minutes to see how far along it is. Every two minutes may see like a lot, but some yarn felts really fast. It's the only way to make sure it doesn't go to far.
You could try hand felting it first in a sink with hot water and swishing it around. I'm not sure how well that would work, but it seems like it would take a lot longer that way...maybe easier though since you don't want it to felt a lot anyway.