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Al Massey

Question on Wootz- specifically, old patterns vs. new...

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Sometime in the next year I plan to try and do a couple of crucible smelts. I recall reading that the ironmasters of old would pick out crucibles from the fire and "slosh" the contents, listening for the liquid sound. 

I wonder if some of the difference in patterning between old and new wootz might be attributable to the mechanical action implied- also, wouldn't doing this also help rid the smelter of air bubbles in the material?

Just a thought...

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Someone has mislead you about wootz.  Originally it was made in small sealed crucibles with approx. 24 of them in the furnace at a time.  Each of them produced a semi-spherical billet of approx. 2.4/2.5  kilos or  about 5 lbs.  The pattern occurred during the cool down time after smelting with the furnace remaining closed so "sloshing" would have been impossible. 

There is a lot  of material online to explain the process.

Edited by Gary Mulkey

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There were almost certainly several different production methods for crucible steel in the middle/near east as there were different centres. The "sloshing sound" I'm taking from a description in Figiel's book. I'd surmise that the size of the desired ingots was often a great variation.

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This thread has more information on Wootz than my brain could comfortably manage in one go.

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Hey Al,

Your thoughts are good ones, but none of the things that you are asking about would make any difference to the patterning.  The shaking of the crucible would be simply to hear if there were any clacking from metal pieces which were not fully melted.  A crucible that was ready would have a fully melted charge and shaking the charge would in a similar way to getting bubbles out of concrete, cause some settling of the charge.  However it would still need to sit long enough after the shake or there would be a risk of having slag inside the ingot after it solidified.

The internal microstructure and microsegregation only begins to form once the ingot starts to solidify and the dendrites start to grow from the outside in.  They will always grow from the same place and only the cooling rate will control the size of the resulting dendrites. 

The dendrites are the core building block of the patterns that are formed, without them there is no pattern it is that simple.  It is what happens during the speed of solidification (size of dendrites) and the roasting period (dissolving secondary dendrites and increasing spacing of banding) and the subsequent forging temperatures (controls carbide shape and cluster sheet structure) which causes differences in the patterning.  All of these patterning factors occur after solidification and are totally unaffected by the shaking of the ingot charge.

One other thing that controls the way the pattern ends up is the proportion of reduction in the thickness of the ingot. Larger ingots have a higher degree of reduction than smaller ingots.  This could explain some of the differing pattern characteristics through different centuries.  Abbott drew a pancake style ingot that was forged edge on, this would have been about 5 inches in diameter and was from a different process which was used in the Salem district, melting steel prills in the floor of a bloomery furnace.  Not all Wootz was crucible steel... unless you consider a quartz grit covered bloomery furnace floor to be a crucible, which technically it is. These are the same pancake style ingots which Joseph Banks received with the cone style ingots, all of which came from southern India.  The ingots from Hyderabad area went to Persia and were not examined by the early scientists in Europe.  The ingots from India, described in the 16th to 18th centuries were not the ones that we think of from Hyderabad/Deccani, or the Persian egg shaped ingots, but they are the pancake, buns of steel which were described to be like the size and appearance of a penny loaf.  Penny loaves were round flat and about 5 inches in diameter. 

Other patterning differences can come from the use of shaped hammers and different forging techniques even if it may not be immediately visible to the average observer.  Also the different trace minerals which are in the ingots can make a difference in the way the pattern displays, contrast etc. 

Hope that helps and good luck with your steel making, I look forward to seeing what you come up with!

Tim.

 

 

 

 

 

 

Edited by Tim Mitchell
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On 6/18/2018 at 3:40 AM, Gary Mulkey said:

Someone has mislead you about wootz.  Originally it was made in small sealed crucibles with approx. 24 of them in the furnace at a time.  Each of them produced a semi-spherical billet of approx. 2.4/2.5  kilos or  about 5 lbs.  The pattern occurred during the cool down time after smelting with the furnace remaining closed so "sloshing" would have been impossible. 

There is a lot  of material online to explain the process.

Gary, there were many sizes of ingots depending on the different uses and also the process used and the location.... and the century.  Some ingots were round flat loaves, others were egg shaped, others were as you describe (from Hyderabad).  The crucibles were sometimes fully closed and sealed, other times they had a hole in the lid to insert a rod, and other times there was no crucible at all (a bloomery furnace floor melt).  The furnaces were in some cases open, heating the crucibles from below, some cases closed fully as you describe (at Merv) and some times able to be uncovered, checked and covered once again such as was used at Hyderabad in their round the clock process.  It was there that they needed to know if the crucibles were ready to remove because of the cyclical process.

As you can see, there were many different processes used in many different locations over a time period of close to 2000 years.  Some crucibles were shaken, others were not but the final product was not controlled by the shaking, it was just a monitoring method. Much has been written on the web by misinformed individuals and some hold the understanding, incorrectly, that there was one "Wootz Process" which there was not. 

The only things that were consistent between all the Pulad/Bulat/Wootz processes was that a high carbon steel was produced and solidified into an ingot through medium to slow cooling and the resulting ingot was forged out into blades, tools or other useful items.  Some ingots did not produce patterning due to insufficient dendritic structure in the ingot (through quick solidification), through incorrect forging temperatures, or through the ingots being so small that there was not enough reduction of thickness in the ingot to make the pattern visible.  The ingots from southern India and Sri Lanka didn't produce a watered pattern as the ingots were rod like and too small in diameter, they were made into scissors, punches etc. 

There are few true researchers in this field and even some of the historical information can not be relied upon 100%.  First hand accounts are the only accounts which are significant and what people said of the ingots in the past may or may not be true.  It is a difficult task to weed out the facts from hearsay and rumour. 

Cheers, Tim.

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