[FONT=Comic Sans MS][SIZE=3][COLOR=DarkOrchid]Fulling requires three things: Change in pH (which soap, vinegar and sometimes just the water itself will do), change in temperature (sudden changes if possible), and agitation.
I find it so interesting that for so many it takes more than one cycle to full items. I generally set my machine for a 15 minute cycle and only once have had to reset it. And I let it run through the spin cycle, too, and haven't yet experienced any problems. And distortion that may occur can be fixed by blocking and/or stretching, I would think.
My tips are to use the hotest water, the lowest water setting, vinegar instead of soap so you don't have to worry about getting the soap residue out, and tennis balls. I buy the dead ones they sell as dog toys and put half a dozen in with my wool stuff. It's worked every time! I've made at least ten pairs of slippers this fall for Christmas presents and they've all fulled nicely.[/COLOR][/SIZE][/FONT]