Tube and Yoke -How \"white\" was white?

[John Conyard]

It sounds like you guys are discussing buff leather,oil tanned leather, producing a buff coloured leather. Alum could be used to whiten it. From the Comitatus website,

The wet skin is oiled or greased, stretched and kneaded until moisture is lost and fat is absorbed. This is a very old process dating back to the first leather preparations. The brain tanning of the USA is linked to this, where brains and smoke were used the same way. There is a view that there is no Roman evidence for oil tanning, yet it
is perhaps the oldest method of leather preparation. In 17th century Europe marine oils were used,and some of the first machines used in tanning were made to help pummel the oil into the hide.

The hides were first soaked, often using lime, dried using sawdust and oatmeal, then oiled. Lime helps the quality of the oiled leather. The ancients may have used wood ash. The shales of North Yorkshire produced alum by large-scale chemical processing from the early 17th century. This is the origin of the white buff leather military belts. The wood ash, alum and lime opened up the fibres of the leather making it easier to oil. Back in classical times I suspect small skins could be oiled successfully without the use of alum or lime. But not large thick skins. There is a reference in Homer's Iliad where he compares the struggles between Greece and Troy to that of a man trying to stretch a huge cowhide soaked in lard. Evidence of liming dating back to Anglo Saxon
times suggests that medieval tanners were using liming to remove hair and open up the fibre structure and would have used this in their manufacture of oil tan buff leather.
Military buff leather can be seen as thick leather, usually between 3 to 5mm, which requires a heavy cattle hide. First of all the hide is washed and then treated with a liming solution which burns off the hair and swells up the hide. This allows the hide to more readily soak up the oils.

By the 18th century a band knife splitting machine was used to split the hide in uniform
thickness. Then the strongly alkaline lime residue was removed from the hide using acid salts. Before the oiling a samming machine like a mangle removed excess moisture. Then cod oil was used for the tanning, and beef tallow as a lubricant.

I am coming around to idea of full hides been made in to buff, and whitened in the process. But it is far easier to make vegetable tanned leather.