Which was invented first the single edge or the double edge? I think it was the single edge. Are both considered to be types of safety razors?
Any razor with a guard between the edge and the skin is consider a safety razor. Even the Rolls is a safety. The first guarded razor was patented in 1770. Guarded wedge hoe/T shaped razors were around before the disposable bladed razors that we think of as safety razors. SE disposable blades evolved from wedges. I think some of Kampfe Star lather catchers could take either wedge blades, or the GEM type SE we use today. Gillette developed the DE as a way to sell disposable blades. His first patent was granted in 1901, IIRC. The first Gillette razor went on the market in 1903. I'm pretty sure Kampfe didn't introduce the first disposable SE blade until 1913. I don't have references. This is just stuff I picked up along the way. Corrections are encouraged.
