Thursday, October 04, 2007

Data from Williams & Nissen smelt

This is some information (borrowed with permission) from Skip Williams - reference his smelting trip to Europe spring of this year (March 2007). Skip was kind enough to send me his draft report on the experiment, featuring the use of the tuyere plate / blow hole system.

The smelting experiments were conducted in an oven similar to the one in the picture below. This design is Michael Nissen’s interpretation of the Espevej Oven which was used in parts of Denmark in the period from 200BC to 200AD. The oven has a diameter of approximately 30cm and a height of 50cm above the blowhole. Air is supplied to the oven through a blowhole in a thin plate that is luted into the oven at the start of each smelt. Reports of Michael’s experiments with this design, in English and Danish, can be found at

The blowhole plate is made of a mixture of local sandy clay and horse manure. The aim is to make the plate as thin as reasonable so that it will not melt in the extreme heat that occurs in this part of the furnace. The plate we used was 30cm wide and 40cm tall. It was approximately 4cm thick. The diameter of the blowhole was around 4cm. Air was delivered from a blower through an air tube that rested on rocks and turf placed in front of the furnace.

This information from Skip, and what is visible on Michael\s web site, is interesting in a number of ways that relate back to our Icelandic furnace experiment series:

1) The general concept of the use of a thin / fire proof section at the tuyere. By controlling the way heat develops over the parts of the furnace that are subjected to the highest temperatures, it is possible to reduce the structure at other places, where temperatures are not as high. (We have seen this same pattern develop, This is especially clear on the bricks used in the EconoNorse test smelter.)

(Skip's photo of the resulting bloom - after sectioning)

2) The quality of the bloom produced. Note that it has a much higher concentration of slag within the mass. You can clearly see how the 'bubbles' of deposited iron have grown inside the mass, slowly filling in and squeezing the slag out as they form. If you compare the cross section from the \proto bloom\ from the first VA smelter at Early Iron 1, you can see an obvious sequence.

I will be using Skip & Michael's layout for the Thanksgiving day smelt. The rock slabs will cover from base up to about 30 cm above the tuyere / blow hole space.

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February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

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