Everyone knows that cell rot is a common occurrence in razors with celluloid scales. Everyone seems to agree that some colors are more problematic than others, for example it's common in the yellowish celluloid scales like those on the DD, but not common in black scales. I wondered why that would be.

Celluloid was manufactured from the mid 19th century until about 1940. It is made from nitrocellulose (gun cotton) and camphor. A lot of people people have long put a piece of camphor into their tool boxes, since it emits a gas that creates a light coating on metal that prevents rust. So clearly the camphor is not the culprit. Looking at 19th century pigments it turns out that one of the most common pigments used for reds and yellows was iron oxide (rust). So, I'm speculating that the outgassing of the camphor is carrying traces of iron oxide (and other pigments) and depositing them on the blade as a thin film. The rust then quickly spreads from that iron oxide rich deposit. What do you think?