I know I'm preaching to the choir, but that rayon in the picture has a paper core for added strength when used for the real purpose as "beauty coil". Like Willie said, it can be removed, but it sure is easier to buy the 100% rayon box instead. That's all I've used for over a year now. Tried cotton, once, and went back to silica, after two hits, until I found the rayon thread here. I couldn't deal with the wet sock taste of the cotton at all. Given they way rayon is produced, it's as pure cellulose as is possible to get and never any black specks of bug parts.