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I Forge Iron

Old style polishing...


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The Holtsappfle book talks about using a burnisher to smooth the surface of wrought iron, and if you apply enough pressure (such as with a two handed and full bodyweight approach) you can get what looks like a hard chromed surface. Certainly the surface is much more uniform and shiny, presumably the iron is being smeared over the slag holes as it is polished. I've read somewhere recently (probably in one of the photos above) about burnishers being heavy weights suspended from the roof and the operator using his bodyweight to move them across the workpiece, suggesting that they are very heavy indeed.

 

I had a flick through a couple of older reference books last night, but couldn't find much. Maybe they are worth a proper looking into by those interested ;)  Namely the works of Diderot (http://quod.lib.umich.edu/d/did/)  and De Re Metallica (http://ia600408.us.archive.org/13/items/deremetallica50agri/deremetallica50agri.pdf

 

I couldn't find anything in the Diderot catalogue, but I'm sure he wrote something on the subject of polishing iron (who wrote about everything else!). Agricola (De re Metallica) wrinting in the late 1500's, mentions the use of crushed emery for polishing.

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Yes, thanks a lot Dave - all interesting reading. Good effort. Burnishing is something I have used for years (decades... ahg!) for silver and gold work. I've neglected it and now realise it is something to have a good go at. I have some old rail track that I can polish up, not yet able to go bigger. (I have vision of an old anvil being hung up...)

 

Frosty, the rotten-stone on question used to be a common stone for sharpening stones over here (UK)before the decent oil-stones - mainly from the US - arrived. Quite fine grained and used for a final sharpening. Decomposed granite is often, but not always, kaolin (kaolinite) a.k.a. china clay.

 

I've just done a web search and see it mentioned as weathered limestone mixed with silica, hmm... Not entirely sure about that; my first degree was in geology and I recall it as being a metamorphosed calcareous sedimentary rock. Metamorphosis generally involves movement down to a higher pressure-temperature regime than nearer the surface. Later tectonics or erosion then expose the rock we see today. The change in the rock's structure and its minerals and chemistry made it more friable and easily weathered, I guess it is this that lead it to be named 'rotten' stone.

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Thanks, I'll have a look through that for case-hardened cooking utensils.

 

In my own library I have found a reference to the historical use of case-hardening for kitchen knives, this is in the book 'Irons in the fire' by Rachel Feild.

However, she has an odd understanding about a lot of metalwork and metalworking processes; so I take her writing on things other than historical fact with a pinch of salt.

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