Leather Makers Part 2

Leather Makers the Gittos family of tanners and leather merchants, 18411841-1991 Lisa J Truttman, Truttman, 2008

Part 2 The industry of tanning Tanning hides to make leather is one of the oldest practices in the history of mankind. Leather’s uses for shelter, clothing, footwear, saddles and other gear for horses, and latterly to cover books such as cherished family Bibles, has meant that the skill was always in demand. Leather is the result of tannin (traditionally derived from the tan or coarsely powdered bark that is soaked and forms “tan water”) binding to the protein in animal hides called collogen which, if left untreated with the tanning preservative, readily degrades by attack from natural bacteria and fungi. Tannin binds to the cross-linked fibres of collogen, protecting and preserving them, and also (depending on the tree species used) lends a colour to the finished product as a dye. This was what Benjamin Gittos referred to when writing of his experiments with the various native tree varieties, in terms of the colour of the final product. A nineteenth century tannery required, according to the American Household Cyclopedia of General Information (published 1881): •

A ready supply of pure water for washing and soaking the skins. This softened them for the next part of the process.

•

Lime pits or places to “sweat” the hides to loosen the hairs on the hide (usually by dissolving the roots).

•

More water to clean the hides again once the hair starts to slip, and then to the “beam house” where the hair is scraped off by hand on beams of wood with long curved blunt-edged knives. All flesh from the inside is removed at this point.

•

Then there was “bateing”, soaking the skins in “bate”, water impregnated with dung, (the American source refers to pigeon’s dung, but other sources refer to animals, such as dogs, as a source). This kept the skins soft, and in a condition to absorb the tan water readily. The chemical that did the job was “muriate of ammonia” from the dung, which bonded to the lime and rendered both soluble and easily washed out of the hide.

•

To prevent uneven absorption of the “tanning liquor”, the hides were immersed in a weak or “spent” tanning solution first, handled two or three times a day until evenly coloured.

•

Then the hides were “laid away”. This involved half filling a vat with very strong extract of bark, then carefully laying the hides in the vat, one at a time, each covered with half an inch of finely ground bark. About a foot of spent tan was put on top of the pile, and then the vat covered with boards. The first layer or period in the vat lasted two weeks, after which the hides were taken up out of the vat, washed clean in the liquor, and then fresh bark and tan liquor applied again. This process continues again and again, the length of time dependent of the intended purpose of the leather and its nature (calfskins had 3 layers, sole-leather 4 to 6).

Depending on the intended use of the leather, it was further treated with an array of chemicals and substances, including gum tragacanth (a topcoat finisher for leather, formerly sold in powder form and mixed with water a little at a time to a creamy consistency, then applied to the leather in thin coats), beeswax (for finishing and shine), dubbing (cod-liver oil and melted tallow, for calf skins), solutions of alum and salt (for sheep skins), quicklime, or saltpetre. Everything in the process depended on pure, clean, running water. Unfortunately, the process didn’t keep that water pure and clean for long. Tanneries, as Auckland developed and started to slowly spread in the nineteenth century, were best out in the country, close enough to road and water transport for access to markets, yet far enough away from settlers and their farm animals so that the polluting effects of their industry on the waterways went without complaint.