Degreasing
September,4th , 2021
Training Session

Agenda………..
1. Fatty spew on leather surface
2. Importance of degreasing.
3. Degreasing methods
4. Defects due to inadequate degreasing.
5. SRC Products Vs Competitor products
6. Formulation
7. Comparative report.

Important of degreasing…..
 Degreasing is of utmost importance for the oxidation behavior of leather.
 Carefully degrease with aqueous degreasing agents (Based on Fatty
Alcohol)and ensure sufficient removal of the naturally occurring residual fat,
which possesses an oxidative potential generating reactive peroxide lipids and
eventually Cr(VI).
 The fattier sheep leather are more susceptible than cowhide.
 Degreasing is most relevant in processing sheep skins, where the natural fat
content is about 10 – 20 % of dry weight.
 Degreasing as a separate process step is not usual for bovine hides.
 The nature of this fat makes it difficult to remove because of the presence of
glycerides and a high melting temperature.

Important of degreasing…..
 Excessive amounts of grease in the skin may interfere with uniform
penetration of tan or dye, causing difficulties in the finishing processes and
creating dark and greasy patches on the finished leather.
 Degreasing of greasy skins is particularly important before chrome tannage as
the chromium salts can react with the greases and form insoluble chromium
soaps, which are very difficult to remove subsequently.

1. In an aqueous medium with an organic solvent and a non-ionic surfactant
2. In an aqueous medium with a non-ionic surfactant
3. In a solvent medium.
4. Enzymatic system
Methods used for degreasing process

Fatty spew
 Definition: Fine white, crystalline coating or light film occurring on dried or finished leathers,
mainly on chrome-tanned leathers, after a short or prolonged period of storage. In most cases
distributed over the entire leather surface, sometimes occurring only in parts. Encouraged by
alternate cold and warm storage, high humidity, on leathers that have not been neutralized
completely and by the action of bacteria and mould fungi.
Testing
Contact with an open flame will melt this coating and it can thus be distinguished from
efflorescence of salt.
 Cause: If the content of natural fat is high, especially with mainly free fatty acid components
such as palmitic or stearic acid, these fats crystallize on the grain surface.
 Remedy: Besides thorough degreasing, fatty spew can be rubbed off with a cloth soaked in fat
solvent, petroleum or kerosene. Subsequent application of mineral oil or chlorinated paraffin
reduces the formation of fatty spew. However, reoccurrence cannot be entirely prevented.
Defects due to inadequate degreasing

Fat stains
Definition: Formation of oily dark-coloured irregular fat stains may occur in the renal
region, on the neck and back part of sheep and lamb skins, some kinds of goat skins, pig
skins and cattle hides, in particular if the raw-stock comes from fattened animals. In
most cases they are due to the excretion of liquid fatty substances. These unpleasant
fat stains can no longer be removed if they form insoluble soaps with lime, chrome or
aluminium salts.
Fat grooves
Found in fine-wooled and some coarse-wooled sheep skins, mainly in the neck or
shoulder region. They occur as raised parallel strips running from the back towards the
flanks and containing increased deposits of fat. Furthermore these sections are often
loose-grained and result in callouses on the grain in the leather due to an inadequate
penetration of tannin.
Remedy: Attenuation is not possible if the grooves are very prominent. Intensive
degreasing is necessary.

Fat soaps
High contents of natural fat react with cationic metallic salt such as chrome, aluminium,
zirconium tanning agents to form insoluble soaps and result in heavy staining.
Remedy: Intensive degreasing and elimination of the emulsified fatty matters before
tanning.
Testing fatty Spew
This test has been developed by Gerber Anderas Ollert. Even if he was not scientifically
verified, his testing work has always been helpful.
1. Add 50-100 ml of tap water in a 500ml lab beaker with a large opening.
2. Cut a piece of leather to be tested so it fits the beaker. Fix the leather with a rubber
band over the opening of the beaker. The leather piece should also fit into the
container.
3. Place the leather with the grain side upwards and close the beaker with it.
4. Heat the water and cook for 2 minutes or longer if the leather is thick. Steam should
emerge from the visible scars.
5. Place the leather piece inside the empty but still wet beaker and close it airtight with
plastic wrap and a rubber band.
6. Leave for 3-5 days at temperatures from 20-25°C. If the leather hasn’t developed any
fat marks during the test, then no fat rash is to be expected by the end customer.

Formation of chromium-VI compounds
 Degreasing is of utmost importance for the oxidation behavior of
leather.
 Remove natural grease, which otherwise oxidize generating reactive
peroxide lipids and eventually Cr(VI).
 Use aqueous degreasing agents (Based on Fatty Alcohol)and ensure
sufficient removal of the naturally occurring residual fat, which
possesses an oxidative potential.

Degreasing formulation
Pickled Wt:_______________
Fleshed Wt:______________
% Reagent Time pH Procedure
100 Water
7 Salt 10' Be= 7
Add Skins
2 Sod.Formate 30'
1.5 Soda Bicarb. 45' 5.5-6.0
0.5 Degreasing Agent 60' Leave over night
Next day 10' Green fleshing by machine
Add chemicals on flesh weight
200 Water 10' Drain & Rins
2 Salt
1.5 Degreasing Agent 90' Drain & Well Wash
2 Salt
1.5 Degreasing Agent 90' Drain & Well Wash
70 Water
8 Salt 5' Be= 7-8
0.5 Sod.Formate 30'
1 Formic Acid 60'
0.5 Sulfuric acid 60' In 3 equal installment each 20'
Leave over night
Next day 10' 2.5-2.8
3 Resocrome A 90'
3 Resocrome A 90' Check cross section
1.2 Soda Bicarb. 60' In 3 equal installment each 20'
3.9-4.0 Run for 5 hours
Pile for 72 hours
SRC Products
1. Resolite 1907
2. Resolite W
3. Evolite 1820
4. Evolite S-87
5. Resolan UF
Competitor products
1. Supralan UFC
2. Sialastol R687
Selected Products

Comparative Report.
Test method: SLC 405
Fat contents/Degreasing efficiency
Products Total Fats After Degreasing Product Efficiency
Resolite W 16.66% 6.87% 59%
Supralan UFC 16.72% 5.64% 66%
Resolan UF 16.55% 5.32% 68%
Resolite 1907 16.90% 6.88% 59%
Evolite 1820 16.54% 6.75% 59%
Evolite S-87 16.65% 4.87% 71%
Sialastol R687 16.45% 4.02% 72%