I block EVERYTHING! How severely depends on the desired texture and feel. I use a gravity feed iron. Cannot imagine life without it. The likelihood of an acrylic garment catching fire is greatly exceeded by the likelihood of a lazy, careless, ignorant mother tossing a carefully knitted and finished woolen sweater into a hot wash load to remove kool-aid, catsup, or grape jelly, if it is not left on a bus, or in a restaurant before it even gets dirty. Acrylics that are 'killed' become soft, drapey items that keep their shape. The Bond knitting frame is my friend. I can keep nieces and nephews in warm fashion and not cry over the loss of yarn or time.