So far, the examples of materials science and engineering that we’ve looked at have been quite physics based and with a leaning towards the militaristic, with two examples of sword-smithing on the trot. Today I thought it might be good to look at something a bit more bucolic, a bit more about the day to day. As a side note, this is also the topic that got me started on this year’s theme: when I was on holiday last year I saw an old mill-stone propped up and it got me thinking about milling and millers, who of course are ‘kenning’ men, in their own way, like smiths.
Modern (industrial) milling is done in a multi-stage process that produces a very even product on a large scale. The process is based around metal drums. Traditional mills, today most frequently found as tourist entertainment, are usually based around two stones, one setting on top of the other, with the bedstone* fixed in place and the runner stone sits on top and moves. Both stones are ‘dressed’**, which is to say that a pattern is cut into the stone surface. The seeds to be ground are fed into the middle and the scissoring action of the stones breaks the seeds open and moves the flour and other material to the outside where it can be collected.
*There is a whole language associated with millstones and milling and deals with aspects of the rocks and the operation of the mill. For example the gap between the stones is important to the quality of the flour and its usability, and the acts of lowering and raising the top stone are respectively tentering and lightering.
** Stones can be redressed when they become worn, but there inevitably comes a time when the stone reaches the end of its useful life.
Millstones have been made from a number of different stones at different times and in different places, but during much of European history the finest stones were said to come from Buhr in France. Strangely though, such stones did not come in one piece but rather were constructed from several pieces of the local quartz, held together with plaster and iron bands.
In terms of speculative fiction and mythology, Millers have been thought of as ‘kenning’ men, probably because of the machinery involved in a water- or wind-mill. There are a number of legends of the Fae folk clustering around mills and making themselves useful – for a price. Again, this may have something to do with the boundary between the natural world, agriculture and machinery that is embodied in a mill.
But in terms of materials, the Tales of Alvin Maker (by Orson Scott Card) came to mind. Alvin is the seventh son of a seventh son, growing up in an alternative version of late 18th/early 19th century America. ‘Knacks’ are relatively commonplace, although there is something of a backlash developing against ‘witches’. Alvin’s father is a miller, and whilst all the family have knacks, it is the uncanny youngest-but-one Alvin who is given the job of cutting millstones from the local(-ish) stone, because the stone seems to cut that little bit more easily for him. Taleswapper, an itinerant bard-like character who is collecting frontier stories for a book in exchange for his labour is helping the family with their latest effort to get a new stone – previous attempts have met with failure and there is a feeling in the air that whilst they cannot cut the stone without Alvin, he might be jinxed, or worse. Taleswapper observes that the stones appear to have been cut whole from the rock face, which should be impossible – how would you cut the back face? Normally a slab would be cut and then shaped. Alvin finishes cutting the shape of the stone and then listens to the rock face; the cutting process has apparently fractured the rock in such a way that the new mill stone has been released from the work. It is so, and as it is worked out of its hole, it turns out the face has come away perfectly dressed, in a pattern that Alvin had not used before but that Taleswapper had been describing earlier, a pattern that was supposed to be longer lasting than the more traditional pattern that the Miller family was used to.
Clearly there is a whiff of the uncanny about this, but what do you expect when you start bringing a seventh son’s seventh son into the matter? In theory, something like this might be possible – you could cut an internal surface without damaging the interior of the bulk. In fact this is already done, sort of, with glass for optical fibres and indeed for trophies and the like where an image is etched on the inside. Rather than cutting, energy can be focussed on a particular plane in order to change the properties, typically refractive, through localised heating of the microstructure. In terms of dressed rock, this is going to be a lot harder because the rock will absorb the wavelengths that we would want to use. One of the arguments in the book is that it’s all about knowing where the rock wants to break, i.e, understanding the microstructure and where any defects and fault lines lie. Whilst this is true, to some extent, and it is a principle that miners and quarry workers, masons and sculptors use on a daily basis, in the context of the book it’s very much a social fig-leaf, there to protect Alvin from other people and from getting too big for his boots.