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Water Power

A Happy Miller Indeed

I’m going to tell you a little bit about how I came to be a Miller.

~ by Karl Grevatt.

Before taking over Charlecote Mill, I worked within building conservation around Oxfordshire and Buckingham. I originally trained as a Carpenter but also worked using lime mortars. My interest in mills was sparked when I worked on Brill Windmill, not far from Bicester – it’s a small post mill and I was fascinated by it.

Following that I was lucky enough to be asked to apply for the William Morris Craft Fellowship, which is run by the SPAB (Society for the Protection of Ancient Buildings) and I was selected to become a Fellow in 2009. The Fellowship is a unique course allowing crafts people, who work within building conservation to further their understanding and knowledge, try different skills and work with experts within their field. It’s spread over a year in two month blocks and gives you the opportunity to travel within the UK and work with crafts-people and experts within their field.

On my Fellowship I decided to concentrate on milling and millwrighting.

On my Fellowship I decided to concentrate on milling and millwrighting and spent some time with mills and millwrights around the UK. it’s then that I joined John Bedington for a week at Charlecote Mill. I was struck by how original and unspoilt the mill was and how traditionally it was run. There are only a handful of traditional mills left running commercially in the UK and I was amazed to see this one surviving so well. I went away from my time there contemplating what it would be like to be a Miller.

A year later (2010) I decided to become a trustee for the Fellowship and help support the course that had opened my eyes and introduced me to my future. I stayed in touch with John and went to help him at times on repairs and maintenance and when he said he was looking to retire, it didn’t take me long to jump at the chance. What an amazing opportunity to use my traditional skills, looking after one building. I also gain my own business and become part of the mill’s history – it was too good not to try!

It was about 2 years in the making from the initial decision to then becoming Miller.

In July 2012 I resigned from my job and went to shadow John for 3-4 months to learn from him and have a crash course in milling. I didn’t know if I was going to get to grips with milling, or running a business for that matter, but I officially took over the mill in October 2012 and I haven’t looked back since. I’m very lucky to be the custodian of Charlecote Mill, I love my job and spending my time looking after this amazing piece of working history. I thank John for his continued support and knowledge and I’m so lucky to have such supportive family and friends.

I’m a very happy Miller indeed! 😄


Karl Grevatt, Miller at Charlecote Mill – A Happy Miller IndeedKarl Grevatt, Miller at Charlecote Mill – A Happy Miller IndeedKarl Grevatt, Miller at Charlecote Mill – A Happy Miller Indeed
Karl Grevatt, Miller at Charlecote Mill – A Happy Miller Indeed
Karl Grevatt, Miller at Charlecote Mill – A Happy Miller Indeed
30th April 2016 / 2 Comments / by / in , , , ,
Essential Elements for Early Iron Smelting

When scouting for an area in which to establish a new iron smelting facility, early ironmasters asked themselves many questions –

Did the area have suitable topography for the construction of a furnace and its charging bridge? Was there a good and plentiful supply of water for turning a wheel? Were the surrounding landforms suitable for constructing water-control features, i.e., dams, canals, headraces, waterwheels, tailraces? Were there plentiful raw materials available in the area, i.e., iron-bearing ore deposits, fluxes, and wood for making charcoal? How could these supplies be brought in if local supplies ran out? Could the finished product be transported away easily? Was there an available labour supply? How would they get to the site? Where will the iron ingots be worked? Should a forge also be built onsite? What products was the grade of iron produced good for? Who has the expertise and experience to manage such a project? How will it initially be financed? It’s any wonder that they ever got off the ground!

The Iron Age occurred after the Bronze Age, so metallurgy was already known. But let’s not forget, we’re talking circa 900 BC onwards for Europe! (yes, that’s 1100 years ago). They needed to overcome the increased temperature required to smelt iron compared with tin and copper. And it was only in the 15th century that the introduction of the blast furnace really got the iron flowing!

Another important aspect of iron smelting is the carbon content as derived from the charcoal that it has to be burnt with. Only a small variation in the carbon content makes a big different to the hardness and therefore uses of the end product. Indeed it is the precise carbon content in the iron alloy that gives us steel! Less than 0.25 % is too little and over 1% is too much!

So in the beginning there were no blast furnaces and no coke (derived from coal). The metallurgists had to make their magic in bloomeries with charcoal, that they derived from carefully selected woodlands. Broadleaved trees were preferred because of their higher carbon content and because they produced a greater heat than coniferous trees. The size of the charcoal was also a major consideration. Charcoal larger than about 5 or 6 cms in diameter was too easily reduced to dust when transported or crushed by the weight of the furnace charge. Charcoal dust was most undesirable because it lowered the efficiency of the furnace. This served as an incentive to conduct cyclic coppicing of the surrounding woodlands, the evidence of which we can often see today!  Charcoal was fragile and was too costly to be transported very far. The demanding charcoal needs of the ironmasters, coupled with that of the other glass works, potteries, and shipbuilding saw Britain’s forests rapidly dwindle.

Bloomeries varied tremendously, but a bloomery was generally a clay and stone kiln construction with a central chimney and an access hole at the bottom. The iron-ore was mixed with the charcoal and hand-bellows got the fire going. When the fuel was spent, the bloomery was emptied out and the spongy metallic lump of wrought iron and slag was recovered.

Bloomery Bloomery-2 RomanBloomery

 

 

 

 

 

 

 

 

As time went on, much was learnt about the fuel and temperature variations based on the emerging product. Water-powered bellows soon replaced the hand operated ones and the bloomeries were made taller. Soon a ramp was required to fill the furnace and careful layering of products was employed. Mistakes were costly, both in time and materials, so I should think lessons were learned quickly and knowledge closely guarded.

The iron-ore and charcoal was added to the furnace via the hole in the top in alternating layers of carefully considered thickness! This kind of knowledge was passed on from ironmaster to apprentice and learned from experience not out of a book!

If a furnace was blown out or extinguished, it had to be rebuilt, causing a one-or two-month delay before high-quality iron could again be made. Therefore, it was imperative that the iron-smelting production process was not disrupted.

But the Chinese were well ahead of the game and were already using a continuous kiln at a higher temperature that was able to drive-off the oxides and liquify the iron. It was recharged at the top with iron-ore, limestone flux and charcoal and molten iron and slag were tapped-off separately at the bottom.

Introducing the blast furnace!

 

Chemistry-in-a-Blast-Furnace

 

It was introduced to the Weald in 1491 or 2, but despite the arrival of the blast furnace in the 1490s, bloomeries were still operating in the West Midlands region beyond 1580. And in Furness and Cumberland, they operated into the early 17th century!  The last one in England (near Garstang) did not close until about 1770.

Waterwheels, bellows, blast furnaces, and the continuous melt!

 

Early-Blast-furnace

 

Blast furnaces were the new fashion. The well-known bloomery was being replaced with the more permanent and larger blast furnaces, with waterwheel-driven bellows and charging ramps.

The monks cottoned on quickly and blast furnaces were thrown up at Abbeys such as Tintern and centres such as the Forest of Dean and Ironbridge emerged.

The technology didn’t change drastically until 1709, when Abraham Darby of the Coalbrookdale Co in Ironbridge introduced Coke (a form of coal) as a fuel in place of charcoal. This allowed the size of furnaces to physically increase, because charcoal collapsed under the weight. So improved were the results that coke was almost universally adopted within 100 years.

 

Another improvement was that of pre-heating the blast air. It was achieved by using heat recovered from the exhaust gases. This enabled the temperature within the furnace to remain uniform and high!

Amazingly, (apparently) you can tell from the texture and colour of the slag whether or not a furnace had a hot or cold blast!

They also pre-mixed the coke and iron-ore and roasted it, producing sinter. This helped to drive-off impurities and improve the iron product.

All in all, a proper job!

15th December 2015 / by / in ,
Big Wheels Keep On Turnin’

Waterwheels are an incredibly versatile bit of kit! Growing up, I thought they were just a clever art installation adorning a wooded valley walk. However, as usual, I was wrong, so very wrong!

We’ve had wooden wheels, metal wheels, vertical, horizontal, overshot, breast and undershot wheels. Wheels for lifting water and rotating drive shafts for a whole host of machinery! Once in motion, the rotational energy could be transferred to gears and machinery, sometimes by leather belts or rods. We’ve had flat grinding stones, edge runners, trip hammers, ore-crushers, textile and paper mills all reliant on waterwheels!

Cast your minds back to 700 BC, this is when the ancient world saw its 1st non-human operated lifting device – the Egyptian Noria. The wheel was desperately needed to irrigate the dry lands for agriculture. It was a vertical wheel with clay pots and was turned by the current of the river – and undershot, if you will. The pots filled naturally at the bottom (dipped in the river) and as it got pushed round the upper buckets emptied into a well-placed trough or aqueduct.

Noriasmall

 

Lovely! Water raised from river to purpose built infrastructure, where upon gravity took over.

 

Another use of the wheel was employed by the Persians in 250 BC to lift water out of the ground like a pump, but driven by animals on the surface – not water-powered – so doesn’t count!

 

The Romans didn’t do wheels by halves (as you can imagine). However, Vitruvius, an engineer of the Augustan age (31 BC – 14 AD) wrote about all things engineering, gave an account of the use of waterwheels, but basically said there was usually no point in using a waterwheel because of all the cheap slaves available!! Madness!!

Barbegalsmall

 

 

Anyway, in Southern France in about the 4th century, they built a superb flour grinding complex on the side of a slope, consisting of 2 runs (side by side) of 8 waterwheels in series. It’s at Barbegal, Arles and was only discovered in 1940!

 

Ever heard of floating flour mills? Well, when Rome was under siege in 537 AD and the Goths cut off their water supply, they ingeniously took their mill operations onto the river. They made barges of floating mills with waterwheels operating between them. The piers anchoring the floating mills in place actually channelled and speed up the flow of water to the wheels – soon the whole of Europe was doing this apparently!

 

 

Meanwhile over in China, they were favouring horizontal style waterwheels. These, dipped in the edge of a flowing water course and span other wheels. Image definitely needed here! They also used the vertical wheel formation from around the 5th century AD, especially for their grinding ‘edge runners’ and trip hammers. Europe didn’t see these innovations for another 800 years!

Back to the UK and what do we know? Well, there seems to have been a medieval boom! Circa 900 AD there were thought to be less that 100 mills in England, but the Domesday Book, an English survey made in 1086 AD, lists 5,624 watermills! Boom!

There were boat mills, moored under the bridges of early medieval London and other cities in the 12th century; eventually to be replaced by structures joined to bridges. And there were tidal mills. Tidal mills were coastal dwellers and operated only when a head of water was caught by dam gates; they were opened as the tide came in and closed before it went out trapping sea water and channelling it through the mill race to the tidal mill. Most rivers sported a waterwheel to grind something or to spin blades for sawing wood!

 

Why the boom? It was because of the increase in grain production and the loss of cheap labour by plagues and wars. Agricultural methods were on the up and it had to be processed without people power.

 

The monks played a huge part – by the 12th century the Benedictine Monks were leaders in hydropower, metallurgy, beer and agriculture. They ran their enterprises around water power, using waterwheels to drive milling, wood-cutting, forging, and olive crushing machinery. It also provided running water for cooking, washing, bathing and sewage disposal! Tidy!

 

DeReMet

 

 

But then there was mining!  In 1556 the book De Re Metallica, compiled by Georgius Argicola, shows us how they employed these beasts in early mining practices – underground as well as overground!

 

 

 

 

The mining industry needed the wheels for 3 reasons;

  1. to lift ore out of the ground and lower supplies down,
  2. to pump the water out,
  3. to crush the ore on the surface using stamps!

 

IMG_6981small WaterwheelsmallStampssmall

 

 

 

 

 

 

 

The main issue was the supply of water and unlike the grinding mills (or cotton mills as we shall shortly see) they had to be sited where the ore was, not where the water was. So elaborate leat systems were created (like the Mary Tavy Leat on Dartmoor) to deliver the water from the reservoirs to the overshot wheels located at the pit head.

 

Armley Mill Water Wheel by Ashley Dace and licensed for reuse under (CC BY-SA 2.0)

There’s more though – the water wheels powered the cotton industry, not just the shipping and mechanisation! In 1771 Richard Arkwright opened a factory in Derbyshire powered by water, filled with his new spinning frames. This was the very first water-powered factory, but many others soon followed. They used increasingly larger wheels to turn gearing to drive an overhead belt system, delivering power to each machine from above. Less workers were required and in France the people smashed the machines in protest.

Also, the clever Cornish used the wheels in the clay industry to crush their clay into powders – like in the Tregargus Valley!

 

So, we have the parched Egyptians, the creative Chinese and the rampant Romans to thank for the early clever applications of the waterwheel, but then every practical profession from thereon for adapting and reinventing the technology to fit their circumstances – until steam hit the headlines in the 1700s that is!

2nd December 2015 / by / in