Flax fiber is often a bundle of individual fibers and tends to be more coarse.

Flax and linen have a refractive index along its length of about 1.58 to 1.60 and perpendicular to its length of about 1.52 to 1.53.

They have a birefringence of up to 0.06 and a positive sign of elongation.

DuPont Company Techinical Bulletin X-156: IDENTIFICATION OF FIBERS IN TEXTILE MATERIALS, December 1961.

This prepares the textile substrate for downstream processes like dyeing, printing, finishing etc.

In general, synthetic fibres do not have any natural impurity.

Added impurities are the additives or chemicals which are added to facilitate certain processes like weaving (sizing) or prevention of static (lubricationantistatic treatment during melt spinning).

It is a polymer of -Galacturonic acid with a variable number of methyl ester groups.

The wax consists of long chains of fatty alcohols, fatty acids, their esters, cholesterin hydrocarbons.

The mineral matter may be water soluble or may be removed by treatment with dilute mineral acids (demineralizationsouring).

Both Fibroin, which form the actual silk fibre and the sericin are proteins.

Silk Microscopic View