How much silk yarn can be obtained from a cocoon?

Catch the cocoons before the moth emerges, and soak in hot water for a time, try 30 to 60 minutes. Start pulling the 'fluff' away and you will come to one thread that starts to unravel. Put aside and do the same with your other cocoons. When you have enough threads to make a yarn of the size you want. Put all the cocoons in a bowl of water, pull the threads through the teeth of a fine comb and start winding those threads onto a cardboard 'bobbin' or old cotton real or a wool winder. Keep going until you use up all the thread. Rescue the moth chrysalis and put it in a safe dark place like a shoe box with a lid with holes in it, and allow to emerge when ready. To mate and hatch more little silk worm eggs to later give you more silk.