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merino sheep swimming in the ocean.jpg

Dyeing wool 

Basic wool stuff II

Really basic


merino wool sheep.jpg


The fibre in the undercoat of sheep is hydrophobic and hydrophilic simultaneously. 

Structure of wool









Outer shell layer of wool fibre. 

Envelops the cortical by forming a sheath of overlapping scales 4

Each cuticle cell in the wool fibre includes a layered structure in mainly five layers 5

  • F-layer

  • Epicuticle

  • Exocuticle A Layer

  • Exocuticle B Layer

  • Endocuticle 

The F-layer and epicuticle are usually marked as the same layer, called the ‘proteolipid layer’, ‘resistant membrane’ or the ‘fibre cuticle surface membrane’ (FCUSM 6

F-layer consists of a lipid layer that provides a hydrophobic feature to the fibre




Without this layer, e.g. delipidated wool with felt-resist treatment, water can be rapidly spread across the fibre surface and wet the fibre 6

The epicuticle layer is made of protein and resists oxidation by chlorine 1

In the general wool process, this membrane is usually avoided to be damage, except some chemical finishes are designed to break down this layer 6

The exocuticle layer is firm and highly cross-linked 1

Acts as a protective shell and resists the wool fibre swells in water. 


Overlapping scale structure creates small spaces between the scales, which allow water vapour enters the fibre slowly  8

The exocuticle has two layers: the harder A-layer and the B-layer  4

The exocuticle A-layer: is mainly made by cystine residues and is highly crosslinked 6

This large amount of disulphide cross-links: Hydrophobic9

Structure of the cuticle 


The weakest part of the cuticle and is less cross-linked, hydrophilic

It has holes which could let the water vapour pass 7

Swells more in the water when compared with other parts of the cuticle
Primary responsibility is to swell the cuticle cells in water and lift the scale edges

Lipid layer

and Intercellular layer& Cell membrane complex

Lipid layerhydrophobic

Cell membrane complex (CMC)

Found between cortical cells and cuticle cells 10 

Cross-linked by isopeptide bonds 10 11 

Specific enzyme is needed 

To learn more about the breeds, dyeing, treatments, spinning, and other knowledge with me,

stay tuned! 

(Usually just literature review ;P)

What are your thoughts?



1 Lakshmanan, A. (2022). Physical and chemical properties of wool fibers. In Wool Fiber Reinforced Polymer Composites (pp. 49–71). Elsevier.

2 Eslahi, N., Dadashian, F., & Nejad, N. H. (2013). An investigation on keratin extraction from wool and feather waste by enzymatic hydrolysis. Preparative Biochemistry and Biotechnology, 43(7), 624–648.

3 Qiu, J., Wilkens, C., Barrett, K., & Meyer, A. S. (2020). Microbial enzymes catalyzing keratin degradation: Classification, structure, function. In Biotechnology Advances (Vol. 44). Elsevier Inc.

4 Ammayappan, L. (2013). Eco-friendly Surface Modifications of Wool Fiber for its Improved Functionality: An Overview. Asian Journal of Textile, 3, 15–28.

5 Woolmark Learning Centre.

6 The Woolmark Cpompany. THE CUTICLE CELLS OF THE WOOL FIBRE. Wookmark Learning Centre. Retrieved November 12, 2022, from

7 Scanavez, C., Joekes, I., & Zahn, H. (2004). Extractable substances from human hair: A discussion about the origin of the holes. Colloids and Surfaces B: Biointerfaces, 39(1–2), 39–43.

8 Wang, L., & Wang, X. (2009). Effect of structure–property relationships on fatigue failure in natural fibres. Fatigue Failure of Textile Fibres, 95–132.

9 Das, D., & Das, S. (2022). Wool structure and morphology. In Wool Fiber Reinforced Polymer Composites (pp. 13–32). Elsevier.

10 Jones, L., & Rogers, G. (2009). 2. Structure and Composition of Wool. Wool Biology and Metrology. 

11 Rice, R.H., V.J. Wong, and K.E. Pinkerton. 1994. Ultrastructural visualization of cross-linked protein features in epidermal appendages. Journal of Cell Science.:1985-1992.

12 Woolmark.. THE CORTICAL CELLS OF THE WOOL FIBRE. Woolmark Learning Centre. Retrieved November 12, 2022, from

13 Jones, D., & Brischke, C. (2017). Nonwood bio-based materials.

14 Mathison (1964), as cited in Brown, R. M. (1994). The microbial degradation of wool in the marine environment.

15 Woolmark. The Properties of wool.

16 Matsunaga, R., Abe, R., Ishii, D., Watanabe, S. I., Kiyoshi, M., Nöcker, B., Tsuchiya, M., & Tsumoto, K. (2013). Bidirectional binding property of high glycine–tyrosine keratin-associated protein contributes to the mechanical strength and shape of hair. Journal of structural biology, 183(3), 484-494.

17 Hearle & Peters (1963), as cited in Brown, R. M. (1994). The microbial degradation of wool in the marine environment.

18 Martin (1990), as cited in Brown, R. M. (1994). The microbial degradation of wool in the marine environment.

Modified in 15th March, 2024.

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