Clickspring – Ancient Tool Technology: The First Hardened Steel
An evening pause: Most of us know that steel in some variety is made by adding carbon to the iron. This video shows how it was done in ancient times.
Hat tip Cotour.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon. from any other book seller, or direct from my ebook publisher, ebookit. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Pretty much the whole ClickSpring channel is required viewing. I binge-watched all his videos over a couple days when I discovered them last year.
“The traditional method of applying the carbon to the surface of the iron involved packing the iron in a mixture of ground bone and charcoal or a combination of leather, hooves, salt and urine, all inside a well-sealed box. This carburizing package is then heated to a high temperature but still under the melting point of the iron and left at that temperature for a length of time. The longer the package is held at the high temperature, the deeper the carbon will diffuse into the surface. Different depths of hardening are desirable for different purposes: sharp tools need deep hardening to allow grinding and resharpening without exposing the soft core, while machine parts like gears might need only shallow hardening for increased wear resistance.”
https://en.wikipedia.org/wiki/Case-hardening
The process is instantly recognizable by the rainbow surface colors it gives – an effect particularly admired on firearms
https://www.ammoland.com/wp-content/uploads/2018/08/Henry-Big-Boy-Color-Case-Hardened-Rifle-Receiver.jpg
Many historic and some modern revolver frames were “color” case hardened using bone for the carbon source producing beautiful blue/brown/tan marl patterns.