Pieces of celluloid in trays to be placed in the oven for drying.
I am not a chemist, but as explained to me, celluloid is a vegetable derivative produced by combining cellulose with nitric acid and camphor. The reulting material produces beautiful pens. But the material has challenges.
Over the years I have visited many Italian pen companies. My visits typically include being shown how the careful store of the celluloid rods. They are typically stores in steel cabinets which are often in a separate building. The raw celluloid is unstable and there have been fires. When you are around the rods, you can smell the camphor.
There is a long history of using celluloid for pens. The first patent was in 1870.
In its natural state, the celluloid has no colour. Add adding dyes and/or pigments results in the final material being very attractive. There is a depth of colour and a warmth to the hand found with celluloid.
The material costs more than resin, and material takes time to cure. If the celluloid is not cured correctly, the celluloid will continue to loose moisture and shrink.
For proper curing I have seen on visits to various pen manufactures, how the pieces of celluloid are placed in trays, and then baked in the trays places in an oven. The baking is done over a for long period of time (months) at a very low temperature.
When I visited with the staff at OMAS they explained the process in detail. In the end, they explained it took about year to cut, cure, and then shape the pen parts to create the finale celluloid pen. If it is done right, then the celluloid if very strong and durable.
Why go to all this trouble? It is because of the detail and colours of the celluloid. Also, celluloid has a great feel in the hand.