International School of Tanning Technology

MODULE 3 COURSE CURRICULUM

The correct process sequences in the finishing of leather are covered:
Pre-finishing processes include: setting out, drying, conditioning, staking, milling, buffing
Film formation
The means of covering defects (pigment vs dyes)
Reasons for finishing
Different finish coats
Chemicals used in finishing and possible substitutes
Water-based vs solvent-based finishing
Film flow and thixotrophy
Solvent surface tension and contact angles
Adhesion and penetration: the influence of solvent contact angle, leather hydrophobicity, dust
Finish machinery: roller coater, curtain coater, spray lines (HVLP, air-assisted, airless air-assisted), electrostatic spraying, powder coating
Impregnation
Removing defects
Acrylics & penetration theory
Corium minor vs corium major junction
Importance of buffing / dedusting

Spraying

Hand-spraying
Gun setting
Spraying defects
Finish formulation for various leather types
Cross-coat theory
Viscosity / filtration of mix
Automatic spray-booth
Viscosity / filtration of mix
Conveyor speed
Rotary spray arm
Pumps
Electronic eyes
Water or extraction system
Drying tunnel heat / humidity control
Nozzles, air and mix lines

Roller coating

Conveyor speed
Doctor blade setting
Viscosity / filtration of mix
Groove depth and pattern
Direct vs reverse
Heated rollers
Roller speed
Roller gap
Roller cleanliness

Curtain coating

Conveyor speed
Pump flow
Weir cleanliness
Wind protection
Viscosity / filtration of mix

Padding

Viscosity / filtration of mix
Rate of absorption / drying speed

Plating / ironing

Temperature
Pressure

Drying of finish

Embossing

Influence of retannage
Groove depth
Temperature / pressure
Glass transition temperature

Polishing

Polishability of the finish

Colour matching

Colour theory
Measurement of colour and computer-aided spectroscopy
Red-Green vs Yellow-Blue description
Colour difference (delta E) and tolerances

Testing of Leather Finishes

Finish adhesion
Rubfastness, crocking
Flame retardance
Taber
Flexibility