I traveled to bladesmith Nick Rossi’s Portland workshop recently to have him explain what metals were traditionally used in axe making in the United States from colonial times through the Civil War. In addition to creating museum quality knives which you can view on his website, www.rossiknives.com, Nick is a frequent teacher at the New England School of Metalwork in Auburn, Maine, www.newenglandschoolofmetalwork.com.
Brant & Cochran: So Nick when a lot of us laypeople talk about axes we say they are made out of iron or steel. We often use those terms interchangeably. Which I know is wrong. What is the difference between iron and steel?
Nick Rossi: Iron is an element just like oxygen or sodium. It is taken out of the ground in the form of iron ore which is simply a fancy word for a rock or soil from which iron can be extracted. The iron in this ore is mostly bound with silicates which need to be removed to create usable iron. Steel is just further refined iron – it is iron to which some carbon has been added through a chemical process.
B&C: We know that the early American colonists made axes and other tools from the time they arrived in the 1600’s. Where did they get the iron ore to make these tools?
NR: One place they got it strangely enough was from bogs and ponds. You have probably seen a spring or creek around which the surrounding ground has a reddish color. That is the naturally occurring iron coming up through the ground. Bogs sometimes have a high concentration of iron which is precipitated out by bacteria. You can see the work of the bacteria from an oily film on the top of the water. This precipitate became a source of the ore which the colonists used to produce usable iron for metalwork.
B&C: How did they turn this bog mud into iron?
NR: Through the bloomery process. A bloomery is a chimney made out of clay or stone. At the bottom of the chimney are pipes to allow air to flow into it to control the heat. The bog ore is layered in the bloomery with charcoal and the whole thing
heated. The goal was not to melt all the bog ore but to create a gooey “bloom.” The carbon monoxide from the burning charcoal reduces the oxides in the ore into metallic iron which falls into the bottom of the chimney and mixes with the impurities in ore called slag. The bloom is then removed from the chimney and beaten with a hammer or “wrought” to remove the slag. The result is usable wrought iron.
B&C: Then what is “cast” iron?
NR: Unlike bloomery iron which leaves you with a glob of iron and slag that must be worked the cast iron process produces liquid iron. The temperature of a bloomery was relatively low and so was the carbon content of the iron produced in one. Cast iron was made in a blast furnace. Into the top of the furnace iron ore, charcoal and a flux material such as oyster shells or limestone were mixed and heated to extreme temperatures by “blasting” air into the furnace. The iron that was created from the blast furnace was usually around 2-4% carbon significantly higher than bloomery iron.
B&C: Was this wrought or cast iron used for axes?
NR: Usually for part of the axe. Both wrought and cast iron are too brittle for the edge of an axe. You wanted to have a steel bit which could be tempered. To make good steel from wrought or cast iron before the 1850’s a puddling furnace was used. In this furnace, the fire did not come directly into contact with the wrought or cast iron. The heat was blown over the top of the iron lowering the carbon content of the iron.
A “puddler” would watch for the point when the de-carbonizing metal reached the desired quality and remove a ball of this puddled steel. This puddling process continued until the invention of the Bessemer process in the 1850’s.
B&C: So after making the iron you had to make steel. Sounds labor intensive.
NR: Yes, this is why steel was so expensive and was just used for the bit of the axe. You could use a softer iron or steel for the axe head, but the bit was a piece of welded steel welded. The New England School of Metalwork offers a class on making an axe using this traditional two piece method.
B&C: Sounds fun. Thanks, Nick.
More information on pre-Civil War iron and steel production and tool making can be found at:
http://flintriflesmith.com/WritingandResearch/WebArticles/ironandsteel.htm
H.G. “Skip” Brack, Art of the Edge Tool: The Ferrous Metallurgy of New England Shipsmiths and Toolmakers 1607 - 1882 (Pennywheel Press, 2008)