silkworms only live for about 28 days, but in that time they increase in weight 10,000 times. Then, they make a cocoon. Workers collect the cocoons and kill the silkworms with steam. Then, they put the cocoons into hot water to soften them. Next, they pull the fibers from the cocoon and spin them to make silk thread. Finally, they weave the thread into cloth on machines called looms.