Advanced Level Tanning Course / Module 1
ADVANCED LEVEL TANNING / MODULE 1
LEARNING OBJECTIVES
Students need to fully grasp the concepts covered on the Intermediate Level Tanning Course.
In addition to the Intermediate Level Tanning curriculum, the following are covered in this module:
Skin Structure
The gross morphology, histology and the chemical make-up of all skin components
Detail on the hair, collagen, collagen-water, glycosaminoglycans and other inorganic and organic structures
Stress is placed on the development of the 1°, 2° , 3° and 4° structures of collagen and the consequent differentiation of structure into tissues
Knowledge of skin structure relative to processing
Collagen swelling curves
Effect of fibre structure on the quality of the leather produced
Skin Types / Defects
Modification of the tanning process to the skin type
Different animal skin types include cattle (calf and adult), pig, sheep (wool & hair sheep), goat, ostrich and reptile
Defects that occur in the natural animal (breed differences), living animals, slaughter, preservation, storage, tannery processes
Recovering hide value
Raw material quality
Hide and skin improvement schemes
Defects caused during wet blue processing
Prevention of grain damage during processing
Reducing veininess during processing
Fatty spews
Preservation
Preparation of the hide / skin for preservation and problems associated with curing
Mechanisms of action of the various preservation methods
Monitoring and control
Bacterial decay and growth conditions - microbiology of the curing process
The putrefaction process
Damage caused by bacteria
The effect of halophillic bacteria on grain quality
Brine curing
Chilling as a means of short term preservation
Biocide preservation
Modern approach to preservation of hides
Rawhide preservation - quality and cost
Beamhouse and Tanyard
Correct process sequences
Role of each process
Chemicals involved with each stage and possible substitutes
How each stage is monitored and controlled
Physical changes to hides and skins during chemical processing stages
The chemistry of collagen modification by preparative stages of tanning
The latest machinery developments, monitoring and controlling
Through feed fleshing machines
Movement of hides and skins in drums, paddles, mixers, multi-compartment drums
Impact of float levels on on mechanical action in processing vessels
Comparison of wooden, stainless steel and polypropylene drums
Tannery automation
Movement and handling in the beamhouse
Sammying machine requirements
Soaking
Reason for the process
Influences on soaking
Latest development to improve soaking
The role of enzymes
Weight gain during the soaking process
The effect of hyaluronic acid on soaking
Practicalities of soaking - various processes
Soaking of brine cured hides
Effect of fat on the soaking process
Effect of soaking enzymes on collagen destruction
Soaking problems
Unhairing / Liming / Reliming
Chemistry of disulphide bridge cleavage, modification of collagen, lanthionine formation and osmotic swelling
Latest developments to improve quality
Influences on the processes
Reasons for the process
Practicalities of liming - various processes
Chemistry of swelling
Effect of temperature on liming
Enzyme applications in the beamhouse
Effect of phospholipids on liming
Hydrogen sulphide - safety and prevention\
Use of lipase enzymes
Reducing natural wrinkles to maximize leather area
Lime splitting - advantages and disadvantages
Effect of the beamhouse on leather quality
Past, present and future liming processes
Avoiding limeblast in production
Controlling opening up in the beamhouse
Diffusion barrier in the unhairing process
Implications of opening up
Deliming / Bating
Ammonium salt deliming process
Chemistry of calcium hydroxide and sodium hydroxide alkalinity
Latest developments to improve quality
How the deliming / bating process is influenced
Enzyme activity
Characteristics of different bating enzymes - bacterial versus pancreatic
Pickling
Reason for the process
Preparation of the hide / skin for the penetration of chrome
Removal of glycosaminoglycans and splitting of fibre bundles
Degreasing
Advances in the degreasing of hides and skins using surfactants and lipases
Solvent free degreasing of sheepskins
Pickling chemicals
Latest developments to improve quality
Physical chemistry of electrostatic swelling and its prevention
Various pickle processes
Effect of temperature on pickling
Effect of pickle chemicals on the quality of leather produced
Advantages of using electrolyte stable fatliquors in the pickle
Bleaching
The mechanism of pigment breakdown
Bleaching agents and their formation in a CIO2 acid environment
Removal of noxious gases and excess bleaching agents
Tanning
Reason for the process
Why tanners use chrome
Factors that affect penetration & fixation of chrome
Hydrolysis of chrome salts
Chrome tanning mechanisms
Ionisation of carboxyl and amine groups
Olation
Oxalation
Basicity
Effect of pH and temperature on chrome uptake
Basification
Reason for the process
Chemicals used
Effect of pH on wet blue substance, yield and quality
Advantages of magnesium oxide for basification
Effect of different basifying agents on pH development during basification
Effect of temperature on basification
Effect of basification on uptake and distribution of chrome
The role of magnesium oxide in causing stains on wet blue
Treatment of wet blue with acid enzymes
New generation fungicides
Penetration, absorption and distribution of fungicides in wet blue
Problems caused by mould
Chemical types of fungicides
Effect of temperature and moisture on machine operations
How process stages influence the quality of wet blue
Technologies to improve the area of leather
Effect of machine processes on yield from wet blue
Factors within wet blue processing that affect yield, quality and physical properties
Testing
Shrinkage temperature
Boil test
Chrome content of effluent / leather
pH measurement of liquor and the skin
Density
Temperature
Speed
Use of microscopy in leather processing