C 6.14. Contraction, shrinkage
C6 damage sub-categories:
C 6.1. Rust accretion, foxing
C 6.2. Glass-like layers
C 6.3. Stains, accretion
C 6.3.1. Handling marks
C 6.3.2. Ink stains
C 6.4. Ink corrosion
C 6.5. Ink loss; fading
C 6.6. Offset
C 6.7. Ink flake off; detachment of the parchment
C 6.8. Tears, splits
C 6.9. Pleats
C 6.10. Cockling
C 6.11. Curling
C 6.12. Pleats, double folds
C 6.13. Folds
C 6.14. Contraction, shrinkage
C 6.15. Internal loss
C 6.16. Edge loss
C 6.17. Blooms; calcite deposits
C 6.18. Micro-biological damage, mould, grazing
C 6.19. Brittleness
C 6.20. Rigidity, stiffness
Shrinkage is a reduction in the volume and dimensions of the parchment.
The localised shrinkage of the parchment is almost always due to the degradation of the parchment, which is the decomposition caused by the oxidation and hydrolysis of the long (ca 300 nm) collagen molecules, which is neatly twisted into a left-handed α-helix by hydrogen bonds, into shorter molecules. The changed chemical properties are accompanied by a change in the density of the parchment and flexibility is lost.