Dictionary of leather terms

Hohenstein

Base coatUsually the first finish coat that is applied to the leather surface.
Basification
The chemical binding of the tanning chemicals to the skin protein. This is achieved by raising the pH slowly in the tanning liquor.
BatingThe softening of skins by treating them with pancreatic enzymes. The enzymes remove unwanted skin components making the final leather soft.
CollagenThe main skin protein that is tanned and which becomes leather. Most other skin components are removed during the beamhouse processes.
ConditioningThe addition of a small amount of moisture into the crust leather for lubrication prior to some of the harsh softening processes that follow (staking, milling).
CrosslinkersChemicals which are used to toughen the finish film and which are also used to improve the water resistance of polyurethane resins and lacquers.
Crust leatherLeather that has been through the dyehouse processes and has been dried, but not yet finished.
DelimingThe removal of lime from the skin usually achieved by ammonium sulphate or ammonium chloride. The skin swelling is reduced as the pH is reduced.
Drawn grain
The wrinkling of the grain layer due to uneven swelling or excess mechanical action during the liming process.
DyeingThe dyeing of the wet blue or wet white to the colour required by the customer.
Embossing A process similar to
plating but instead of a smooth plate being used, an engraved plate is used, which presses a pattern into the leather surface.
FatliquoringThe addition of oils or fatliquors to the leather to make the leather soft. The more fatliquor that is added, the softer the leather becomes.
FixationThe use of formic acid to lower the pH of the leather resulting in the binding of the dyehouse chemicals to the leather.
FleshingRemoval of the fatty layer usually by fleshing machine which helps with the penetration of chemicals into the skin in subsequent process stages.
Handle modifiersChemicals such as waxes or silicones which are used to change the feel of the surface of the leather.
Hide
The skin covering from a large animal such as a cow or ox or bull.
LacquersChemicals that are used in the top coats of finishes and which give the properties that the top coat must have.
Leather finishingThe application of a protective film onto the leather surface to make it more durable and to try and hide as many defects on the leather surface as possible.
LimingThe swelling of the skin using lime. The swelling is important for the proper opening up of the fibre structure which is important in the making of leather.
MillingThe tumbling of crust leather in wooden or stainless steel drums to soften it.
NeutralizationThe removal of acidity from the wet blue or wet white which allows the dyehouse chemicals to penetrate through the cross-section of the wet blue or wet white.
PicklingThe lowering of the pH of the skins using sulphuric acid or formic acid preparing the skin for the tanning chemicals. The tanning chemicals penetrate easily into the skin at low pH.
PigmentsColoured chemicals that give the colour to the leather finish but which also help to hide defects on the leather.
PlatingA process whereby leather is put in a press under high temperature and pressure. Plating makes the leather finish very smooth and helps it stick to the leather surface.
RechromingThe process whereby chrome is added to the wet blue or wet white. Usually used to level out chrome differences from batch to batch or used when making very soft leather.
ResinsChemicals such as acrylics, butadienes and polyurethanes which bind the pigments to the leather surface during the finishing of the leather.
RetanningThe use of various types of chemicals to give the leather the properties that the final customer wants i.e. softness, fullness, etc.
SammyingThe removal of water from hides or skins after they have been tanned.
Scud
Small amounts of hair left behind on the surface of the hide or skin after the liming and unhairing process
ShavingThe accurate reduction of the thickness of the skin. Usually done at the wet blue or wet white stage.
Side
A hide that has been cut down the backbone into two sides.
SkinThe skin covering from a small animal such as a sheep or goat or ostrich
SoakingUsually the first process in the tannery where any water lost during the preservation process is re-introduced into the skin making is soft and flexible.
SplittingThe cutting of hides into two or more layers and thus reducing the thickness of the original skin. Usually done after the liming process or when the skin has been processed into wet blue.
StakingA vigorous softening process where the leather is stretched and pummelled by machine which separates the leather fibres which have become stuck together after the drying process.
TanningThe addition of tanning chemicals to the skin.
Top coatUsually the final finish coat that is applied to the leather and which must give the scuff resistance and final feel of the finish.
UnhairingThe removal of the hair from the skin. This is usually achieved using sodium sulphide or sodium hydrosulphide.
Wet BlueHides or skins that have been properly tanned using chromium sulphate as the tanning agent. Wet blue is an internationally traded commodity as it is stable as does not putrify.
Wet WhiteHides or skins that have been tanned using aldehydes as the tanning agent.
Wetting backRe-introduction of water into wet blue or wet white. Usually the first process in the dyehouse