Fatliquoring and Dyeing
1.0 Uses, purposes and effects
1.4 "run" and handle
1.5 Ability to take up or resist water
1.6 As an aid to the resistance to abrasion
1.7 As an aid to the resistance to becoming dirty
1.8 As an aid to the resistance to chemical attack
1.9 To improve tensile strength
1.10 To improve colour
1.11 The effect achieved depends on
a. Type, state of leather
b. Type, quantity of oil, fat, wax or grease applied
c. Method of application
d. Whether it is all on the surface or has penetrated into the internal structure
2.0 The application of emulsions of oil to the leather. Process only about seventy years old.
2.1 Emulsion: milky liquid consisting of water holding in suspension minute particles of oil or resin by the aid of some emulsifying agent.
2.2 Best emulsifying agents are soaps. Na Salt, Olive oil soaps (often specified), Sodium Oleate (to be preferred)
2.3 Originally involved emulsifying grease with oil and smearing it on leather.
2.4 To provide light leather with a greater softness and flexibility.
2.5 Processing is done in drum. 1% oil put in leather plus half its weight in soap
2.6 Many soaps will come out in leather as spew with pH less than 7.
2.7 Leather must be neutralised so that soap will not break in outer layers.
2.8 Sometimes add a little alkali to fatliquor to prevent soap breaking too early.
2.9 Egg yoke is a valuable fat with good filling properties.
2.10 As amount of chrome in leather goes up less fat is needed. But more chrome can lead to a coarser grain).
2.11 COD Cheap; gives soft leather, raggy in flanks, will smell if a lot present. danger of dark patches in flanks.
2.12 SPERM usage discontinued for environmental reasons. gave a dry handle, less soft than neatsfoot, softer than cod. was sometimes used instead of neatsfoot. Proved difficult to substitute.
2.13 NEATSFOOT expensive; leather very soft, beautiful. Used with glace kid and the best calf. fast to light. Not economic with vegetable tans as its effects are not obvious.
2.14 Sulphated oils (or sulphonated) stand up to acids better than soap dispersions. They are good, fine dispersions. Penetrate well into leather before being deposited; give good lubrication. Said not to soften as well as raw oil.
2.15 Sulphated oils made by treating fish, animal or vegetable oils with 10-20% Sulphuric acid at very low temperatures. Sulphonated similar but higher temperatures used. Sulphonated more stable to acids.
2.16 Sulphated and sulphonated oils are often mixed in fatliquors.
2.17 Sulphited oils made by treating oil with Sodium bisulphite. More acid stable than sulphated or sulphonated Give better lubrication to leather.
2.18 For fatliquoring high temps, low float and a time of 20 to 45 mins is normal.
2.19 Leather out of drum should not be greasy.
2.20 Horse leather up (overnight preferably) to cool
2.21 If put hot out of drum into any drying system will come out hard, and perhaps also loose.
2.22 Control of size of globules important to get proper uptake.