Table III

Cellulose Fibers

Fiber Part of Plant Used Micron Size Range* Fiber Length Range Fiber Structure Elasticity Flammability Felting Potential Suitable Uses
Cotton (American, G. hirsutum) Fruit 4 - 5.5 micronaire 21 - 32mm Flattened twisted tube, lobed cross-section Low High None General purpose. 90+% of world cotton production
Cotton (Colored, Gossypium spp. and hybrids) Fruit 2.5 - 4 micronaire 12 - 30mm Flattened twisted tube, lobed cross-section Low High None Specialty garments and household goods. Minimim length for machine spinning: 23mm
Cotton (Egyptian, G. barbadense) Fruit 3 - 4 microniare 35 - 44mm Flattened twisted tube, lobed cross-section Low High None High quality sheets and towels, shirting fabrics
Cotton (Sea Island, G. barbadense) Fruit 3 - 4 micronaire 35 - 64mm Flattened twisted tube, lobed cross-section Low High None High quality sheets and towels, shirting fabrics
Flax Stem 15 - 17 µm To 1m, 20 - 30 mm ultimates Polygonal lumen, nodes along length Low High None Line: fine household goods, shirting. Tow: coarse fabrics, rope
Hemp Stem 17 - 23 µm to 3m Irregular oval lumen, nodes along length Low High None Any as flax, only coarse tow easily available
Jute Stem 15 - 20 µm to 4.5m Polygonal lumen Low High None Sacking, rope and carpet backing
Ramie Stem 30 - 50 µm ~125mm Irregular oval lumen Low High None Linen-like garment fabrics

Note on cotton fiber diameter: Cotton fineness is measured in micronaires, from a sample measurement of airflow in a controlled environment. Finer fibers (low micronaire) have a higher surface area to mass ratio and allow less airflow. Micronaire is technically unitless, but is understood to be a measure of linear density (micrograms per inch.) Cotton producers, researchers and processors use this measurement to describe cotton fiber, along with other units of linear density such as tex (grams per 1000 meters.) Typical linear measurements for the diameter of "ideal" (assumed round) cotton fibers are in the range of 12 to 20 µm. In general, green cotton is the finest type.


Maximum 192 points

Examiner 1: 183
Examiner 2: 168

Examiner 1 gave 21 points each for the American, Colored and Sea Island cotton items and the full 24 for the rest. For American, the comment is that cotton is normally referred to as a seed hair. The column was marked "Part of Plant Used" so I put fruit. I felt this was appropriate because it is the part that is harvested and then processed to recover the cotton fiber. Flax, hemp, ramie and jute also are also extracted from a plant part that is mostly discarded, although by a different process. The comment for Sea Island is that it doesn't get any longer than the Egyptian varieties. I know I found a source that said Sea Island can be much longer, I will have to go look for it again.

Examiner 1's comment for colored cotton really bothers me. "Usually less than 18 mm" may be true for unimproved wild varieties, but clearly there is longer staple cotton available because it is regularly used for industrially processed textiles. 18 mm is too short for machine spinning. Sally Fox's naturally colored cottons have been available for some years now and she recently developed a Sea Island cross with a staple length more than twice that of wild green cottons. I spoke to Sally Fox myself to get technical details of her colored cottons because most of it cannot be found from published sources.

Examiner 2 gave 21 points for each item, noting the lack of detailed flammability information as with the protein fibers.

This table was a problem because of the "Micron Size Range" column. I was able to find some representitive size data for the silks, which are generally measured in deniers, but cotton is almost never described in terms of diameter in microns. I could find only the most vague references to micron measurements. I added the note to the table to try to deal with this, but I was unsure if using micronaire units or including the note would be acceptable. The mentor thought it would be ok, so that's what I did. This is one of those "FOLLOW THE DIRECTIONS" things I was trying to figure out.