Neutralisation
Wet blue starts acidic. The pH is raised gradually to an article-dependent target, with bath and cross-section measurements used together.
LEATHER MANUFACTURE
Post-Tanning Operations
Understanding how wet blue is transformed through neutralisation, retanning, dyeing and fatliquoring.
FROM WET BLUE TO THE WET-END
Preparing and engineering the leather
After shaving, chrome-tanned leather has a uniform thickness but its chemical condition is not yet suitable for the next stages. This material follows the leather through the connected wet-end sequence rather than treating each operation as an isolated recipe.
Neutralisation prepares the leather by raising pH in a controlled way. Retanning then modifies structure and properties, dyeing develops colour through the cross-section, and fatliquoring lubricates the fibres to create softness and flexibility.
NeutralisationControl pH and fibre opening while preserving grain tightness and chrome stability.
Retanning & dyeingEngineer properties, manage penetration and understand how earlier processing affects colour.
FatliquoringLubricate fibres, control emulsion stability and build softness, handle and flexibility.
A LOOK INSIDE THE MATERIAL
One continuous process, not four disconnected lessons
Retanning
Different retanning systems change fullness, softness, grain tightness and handle by modifying and supporting the fibre structure.
Dyeing
Good dyeing requires penetration before fixation. Uneven colour can reveal problems created much earlier in processing.
Fatliquoring
Fatliquors coat and lubricate collagen fibres so they remain able to move after drying, producing softness and flexibility.
What the learner should understand
The important lesson is the connection between stages. Neutralisation controls uptake; retanning changes structure; dyeing reflects the condition created by earlier processes; and fatliquoring builds on everything that has gone before. Operators therefore learn to interpret process conditions rather than simply follow additions on a recipe.
The bath tells you what you are doing. The cross-section tells you what has actually happened.