2. • All hides/skins are highly susceptible to
decomposition by bacteria
• In order to protect them during transport &
storage, they are preserved by various
means
• The aim of curing is to remove water from
tissue to such an extent that no
irreversible changes occur in the collagen
fibres
3. • It is only after preservation that the raw hide
becomes a commercial product
• The best quality raw hides come from
temperate countries (surroundings & type of
management)
• The best supply for sheep & goat skins in the
world market come from Australia, New
Zealand, India, Greece, China & Spain
• The best skins with regard to grain quality
come from Europe.
4. Preservation of Hides & Skins
1. Drying (removal of water) is the most
obvious method of curing
Drying does not kill bacteria but the very low
water
content prevent their multiplication & they
cannot
form any decomposing enzymes (bacterial
activity
ceases when hide contains < 14% moisture)
5. • The dried hide (10-25% moisture) returns
to its raw condition upon soaking
• Drying should be gradual & even (the
parts that get too hot may gelatinize &
dissolve away when put in water
6. Options for drying:
a) Ground drying:
The hide is spread with flesh side up on the
ground & wooden pegs used to straighten it
A disadvantage of this method is that
there is poor ventilation on the
ground side & very high temperature
on exposed flesh side
7. b). Sun-drying on poles:
The hide is laid or hung on poles or ropes
There is good ventilation and quicker
drying but heat damage & rope marks may
result
8. c). Frame-drying under shade:
Hides are dried on permanent frames that
are located under shade
Good ventilation & shade ensure slow
uniform drying; If the fastening ropes are
too tight weakness and thinness may
result
9. • Dried hides require careful packing
(bending & excessive compaction cause
cracks)
• Dried hides are prone to insect attacks
(insecticides are applied to prevent)
• Anthrax may be present on dry hides (the
danger disappear after liming in the
tannery)
10. 2. Wet salting:
• The flayed hide is spread out, flesh side up,
on a concrete floor & well sprinkled with salt
(coarse grained salt spreads better)
• A second hide is placed on top of the first
and sprinkled also with salt; the process is
repeated until the pile is 1.5m high
• Amount of salt used is 25-30% of raw hide
weight
11. • Bacteria in marine salt can give rise to red
patches on the flesh; This can be prevented
by mixing soda ash and naphthalene with the
marine salt (44kg salt, 0.5kg naphthalene &
1kg soda ash)
12. • An alternative & more efficient way of wet
salting is to hang the raw hides in a very
strong salt solution (14kg salt in 45.5kg
cold water) for 12-14hrs followed by
draining & piling (this gives uniform salt
penetration)
• Both wet salting & brining require large
quantities of salt & the cured hide remain
damp
13. 3. Dry Salting:
• The flayed skin is salted by either of the
above methods and then hung up to dry
• This reduces weight & transport cost
14. 4. Pickling:
• Done on hides after unhairing, liming &
fleshing
• After unhairing, liming & deliming the skins
are
washed & then gently drummed for 2hrs in
a
12% salt solution (5.5kg per 45kg cold
water)
at 10-21oC to which 1-1.2% sulphuric acid
15. • After pickling the hides may be stored for
several months (temperature should be
<32oC otherwise acidity may cause
damage to skin)
• Putrefying bacteria will not thrive (stop
activity at pH 2) but mould growth can
occur therefore fungicides need to be
applied
• Pickled skins should not be allowed to dry
(acids or crystals may cause damage)
