If you have a maxed out tradeskill trophy (i.e. 15%), you summon a satchel and hand it into Jolum in the tradeskill area in the bazaar (near the PoK zone). Jolum gives you this (Artisan Essence) back. Now you put this essence (on it's own) into an appropriate tradeskill container (e.g. oven if you summoned the essence with the Denmother's Rolling Pin). You get back a 12-slot permanent 100% weight reducing bag.