How much weight can a single strand of hair hold before it snaps? Hair is surprisingly strong. A dry strand can support a load similar to copper wire of the same thickness. You tie a hair strand to a stand and hang a small hook on the other end. You add weight slowly and record how far the hair stretches at each step. When it breaks, you note the final weight. Then you compare treated hair to untreated hair. Bleached or permed hair is weaker. Wet hair loses up to 30 percent of its strength. You plot the results on a stretch-versus-weight graph.