The gold leaf would be beaten from a small ingot of gold. This would involve sandwiching the gold be-tween a kind of vellum or skin, aptly called gold-beater's skin. The process would continue until a pack of 500 gold leaves was created with each leaf separated from one another by the protective gold-beater's skin. The finished gold leaf was an unimaginable 0.000125 mm thick! To produce a piece of gold leaf in this way is an incredibly skilled task and goldbeaters would pass their cherished skills down through the family. It was the goldbeaters themselves who knew how to make the skin, which involved a similarly secretive and coveted technique. As such the process and ingredients involved were seldom written down.
Goldbeaters skin is made from part of a cows intestine, the outer layer of the caecum to be precise, which is also called blind gut or even the appendix. The outer layers of the blind-gut are carefully stripped off into sheets of around 60 cm in length by 25 cm in width. They are then cleaned of fat by dipping the gut in a mild alkaline solution and scraped with a blunt knife. The cleaned gut is then stretched over a frame. One quite remarkably quality of this material is that separate sheets can be joined or welded when wet by carefully rubbing the overlap of the two sheets. Several layers can be made this way as well, for example, airship gasbags usually consisted of up to seven layers of skin.
The living tissues in the sheets grew together making a seamless and Hydrogen proof join. As well as being impermeable to Hydrogen it was also light and very strong, making it the perfect gasbag material! However it was very labour intensive and time consuming to produce. Supply of goldbeaters skin ran out during the First World War, forcing the Zeppelin Company to recycle the material from older airships as well as use an inferior artificial substitute for the construction of the gasbags.
Airship gasbags were big things! For example, Hindenburg had a gas capacity of nearly 212,000 cubic meters. So it becomes clear that these sheets, each one being painstakingly prepared by hand and fused with each other and done so in many layers, were also required in unimaginable quan-tities. Moreover, when only two sheets could be obtained from the intestine of one cow, we realise that an awful lot of cows were required to service the demands of the airship industry!
In reality, the gut was obtained as a by-product of the meat industry. But over 200,000 sheets of gold-beaters skin were needed for the gasbags of a standard German naval airship that was used during World War One. But this type of airship was small in comparison to later models. The American mili-tary airship U.S.S. Shenandoah used 750,000 separate sheets of goldbeaters skin for its gasbags.
Never ever heard of 'gold beater' skins. I have heard of gasbags, tho.
ReplyDeleteheels bells that's a lot of poor cows.
ReplyDelete