For its mechanical strength, unbreakable, waterproof, for ease of processing and above all for the almost infinite capacity of being made in different colors, from the mid '20s celluloid became the main material used by fountain pens manufacturers and it remained so until the '40s when the [[plastic resin]] started to spread. | For its mechanical strength, unbreakable, waterproof, for ease of processing and above all for the almost infinite capacity of being made in different colors, from the mid '20s celluloid became the main material used by fountain pens manufacturers and it remained so until the '40s when the [[plastic resin]] started to spread. |