1. Hard Rubber (Ebonit) back
The first and most succesful material used to manufacture pens. Natural rubbler is vulcanized whith approx. 30% of sulfur by aplying heat and pressure. The hard rubber rods can be worked on the lathe, are resistant to any agressive liquids and can be polished to a shiny gloss. The only disadvantage is the tendency to change colour with light and water, as the sulfur then turns up at the surface. Till the end of the thirties, hard rubber was the dominant material for pens. Hard rubber can best be identified by the smell of sulfur (foul eggs).