Flash string will burn quickly and completely when get in touch with lighter or spark. There will be no smoke or ash during the ignition. It is often used as a fuse for lighting other items like firecrackers.

Nitrocellulose string should be store in wet conditions and will become a little yellow at the same time. Dry the nitrated string before using and the string will be white again. It will cause no degradation although stored for many years.