A re-enactment group I know are good friends with a venue in the Lakes District, near where iron used to be mined. They are interested in carrying out a medieval iron smelt at some point in time.
This blog post therefore is a wee summary of what I know about it at the moment, based on one particular interesting paper I found recently, along with some pictures.
The paper is this one:
There are many topics that the paper brings up, all of which are important if you wish to have as easy a re-creation of a medieval bloomery as possible. The simple fact is that our ancestors spent generations refining their metallurgical techniques, and ignoring what the archaeology and practical experiments tells us would condemn us to spend many years in re-creating the same things as have been done before. I see no need to do that, because, as with Tudor bronze casting, it will be quite difficult enough as it is even if we do everything right, so it is important to learn from previous attempts.
In the abstract is a list of topics that are examined that seem to me to be very important and I will first discuss them below based on my knowledge without having properly read the paper:
the nature of the furnaces, the bellows and blowing rates; the ore, charcoal and clay
types, quality and treatment; and the operating conditions, the products and the losses of material through the refining process.
To start with, the nature of the furnaces. I have been unable to find out much about lakes district furnaces in the late medieval period, but it seems obvious to me that since blast furnaces had not reached that part of Europe, they were the typical chimney shaped bloomery furnace. This will have to be fully confirmed by reading more widely in the archaeological literature.
They are called bloomery furnaces because they produce a ‘bloom’ of iron, like you can see being hit with hammers in the darkness in this photo:
The furnaces would have looked something like this, with the second photo showing slag flowing out of the furnace: