Before picture is first, after is next ... (double click on the pics to see the detail.) The only discerning difference is the loose knit of the piece before felting.
I was searching for on-line instructions for felting, and finally found one page that had this topic, but the instructor said she had friends that had done that, but hadn't done it herself, so she only had a few tips.
I'm in a camper, no top-loading washing machine is available, and it'll be several days before I can felt this awesome bag I just finished so ...
I figure the washing machine has hot water only as hot as the water heater, and the agitator in the washer just keeps the piece moving 5 - 12 minutes, I've felted several pieces in the washer now.
Oh my goodness, I did not know that when you put your fine knit piece in the hot water IT STRETCHES FIRST, I mean it gets huge and misshapen.
Anyway, I got the sink full of the hottest water from the water heater, then kept a pot of boiling water going behind me, to add to keep this water hot, added a little liquid detergent, and started agitating.
A couple of hints, I started using a wooden spoon to stir to keep the knit piece moving, it didn't start shrinking and felting at first, I was uneasy about this, but knew I could rinse in cold water, dry it out and felt it in a top-loader whenever I was near one, some day.
The wooden spoon had some splintery places, where the wood had split, and the first snag to the wool, I started scrounging for a different stirring tool. This ended up being a plastic pancake flipper. Worked perfect, just keeping the piece moving in the water was the goal. Each time the water cooled down enough to put my hands in the water, I squeezed the piece several times from every direction, turned it inside out and did the same, it started felting in about 20 minutes. Now the hubby comes in and some friends are here wanting to go to dinner. I rinsed in cold water, laid the bag out on a towel and walked away...reluctantly.
The next morning I got back at it, hot soapy water, teapot full of boiling water, pancake flipper and walla!! It started felting in about 10 more minutes, I did a lot of handling of the item towards the end, and it is amazing (IIMSSM*).
Now this ended up being more like 1 1/2 hour project to felt rather than the 5-12 minutes in a top-loader, but I'm glad I did this, I felt more like a pioneer woman, closer to the earth - whew be prepared for the odor, also. Wet wool, and some yarn, I think it's the dye and the fact that fibers lay around and absorb odors, but the initial odor was really strong, kinda like the dirty lamb walked into the kitchen from the rain ... imagine.
*IIMSSM If I might say so myself!
Not an expert yet, but still trying!!