I’ve become aware of a very thin 100% cotton available in 19 colors.  It is made by Swiss company  Creation Baumann, called Balloon Plus 415, and distributed worldwide.  According to Testfabrics, the US distributor,  this line is dyed with reactive dyes.  I’ve experimented a bit with it, and like most airplane cottons it should be washed before use. It is 73 g/m(2) and is an astounding .oo5 inch thick– the airplane cotton I have averages .008 inch.  Creation Baumann also makes a 100% linen called Loris 173, which is thicker at 187 g/m(2) and around .010 inch.  It is made in 12 colors.  Both can be manufactured to custom colors, if you happen to need 260 yards.

The only downside are the available colors, which are more oriented for designers rather than books, but the medium brown seems quite useful.  I can imagine these fabrics being used on their own, or as a base for additional toning, which I haven’t tried yet.  They also seem useful for other types of board attachment, rebacking, etc. when a thin, strong, natural fiber is desired.