Dear Friend Kokotailo,
Thanks for your message.I think you are more than excited to show that Iron artefacts were not prevalent in India before 9the Century A.D. I hope your statement date about Iron artefacts in China about 6th Century B.C is confirmed.If any change pl let me know. Now let me classify my message : 1) Indus valey civilization Iron laddle ,1800- 2000 B.C 2) The laddle acquired from a Collector. (does it belong to Indus valley civilization) As far as my First message was concerned whether the Laddle I acquired is actually as old as Indus valley civilization ,1800 -2000 B.C as per the Collector.If not then I requested a reasonable reason from the Group Members. Well, My reason for why I believed it to be belonging to Indus valley civilization had been mentioned in the previous message.Apart from that I have no idea about it. But if you think that because Iron was not made or even INVENTED in India before 9th Century A.D. Then I would definitely deny your statement.As far as Iron artefacts in India are concerned I would say I am more aware about its existence in India about or before 2000 B.C. Also the reference I had mentioned clearly suggests the cire perdue method of Casting, which not only persisted to Brass and Gold but also included Iron and Zinc.I would be more than glad to hear from you that when do you think Zinc was first discovered in India and rest of the world. As you said Wiki is just for guidance and not as a valid proof.I would say pl refer to http://tinyurl.com/38579f . It is from a Google Book, written ,published by the Conference on Investment casting ,NCIC 2003 at the Durgapur,WestBengal,India Central Mechanical Engineering Research Insitute. I Hope you dont find Google Books unreliable.And you are comfortable with the Mechanical Engineering Research Institute , Or could visit it personally to challenge them about their Papers in the National conference on Investment casting.
Secondly going into how many degrees Celsius is required to melt Iron, copper and Gold and other metals is a Long subject,I would be glad to rather confine the message to Iron casting method and Iron artefacts in India as about 2000 B.C. If you wish We would discuss the topic of temperature for casting metals in detail later or in private. I would just like to conclude that, whether Ancient Indians were aware of which technology was not a matter,but what We are aware of those Ancient Technologies in India is surely in Doubt. Regarding the Iron Pillar that some one stated to be of 4 th Century A.D. My dear friend could you pl explain me what research made you conclude that it was not of good quality Iron and had much phosphorus init. Because it would of much help that you have solved the Big mystery which other websites are still exploring. Regards, Nirav
--- On Tue, 3/18/08, Robert Kokotailo <robert@calgarycoin.com> wrote:
From: Robert Kokotailo <robert@calgarycoin.com>
Subject: [Ancientartifacts] Re: Indus valley civilization Iron Ladle ,1800- 2300 B.C
To: Ancientartifacts@yahoogroups.com
Date: Tuesday, March 18, 2008, 1:11 PM
At 11:19 AM 3/18/2008, Ancientartifacts@ yahoogroups. com wrote:
Thirdly , I read in a message that There was No
casting method in the period of Indus valley civilization
belonging to mature harappan period 1800- 2300 B.C.I would like
to request you to pl refer
Metallurgy and Jewellery section in http://tinyurl. com/f9jyx
< http://tinyurl. com/f9jyx>
I did not say there was no casting method, I said there was no casting of Iron. Gold and bronze casting were well established technologies by then, but iron was not even a known metal at the time. Your reference does not say anything to dispute this.
Casting iron is much more difficult than casting gold or bronze, mainly because of the much higher temperatures needed to melt the metal. Pure Iron melts at 1535 degrees C, which is about 2800 degrees F. Ancient Iron was not pure, and the actually temperatures needed could be a little lower but not a lot lower. Steel is even lower, but there was no steel until fairly late in the iron age.
To cast ancient iron you have to get the fire hot enough to not only melt it, but to stay molten until it fills the mold, which mean several hundred degrees higher than it's melting point. That temperature will depend on the size of the object being cast, but for a laddle this size it would certainly be in the temperature range of about 3000 F. In spite of one website I found that contradicts this, building a fire big enough to melt a quantity of iron, and maintaining it at least 3000 degrees F, was simply not possible for most ancient cultures. They could get it to 3000 degrees briefly with bellows blowing air onto the fire, but to maintain the temperature a continuous air flow was needed, and the early simple open-close type bellows most cultured used could not accomplish that because it only pushed air out while closing, and not while opening.
The technology that allowed the Chinese to melt and cast iron in about the 6th century BC, was a push pull (rather then open close) bellows with a flapper valve and two outlets both pointed at the fire. It operated much like an accordion and no matter which way the bellow was moving, one side of it was pushing air out to the fire, giving that continuous flow.
Copper melts at 1984 degrees F, which is the minimum temperature needed to make bronze, but once the bronze alloy is made the melting temperature would be slightly lower for most bronze alloys. Gold melts in a similar temperature range. A fire in the 2000 degree F range was all that was needed to cast gold or bronze, and that is a full 1000 degrees lower than for iron casting.
So it all comes down to their bellows technology, with a continuous flow bellows appearing in China by the 6th century BC, but not in Europe until about the 9th to 10th century AD, with India and the middle east somewhere in between.
I was just researching forge welding of iron and it appears forge welding iron requires temperatures of at least 2400 degrees F. This is still on the high side for most ancient cultures but enough lower than the melting temperature that some cultures will have been able to develop forge welding of iron before they developed iron casting technology, but as far as I can see, iron forge welding was not wide spread until the early middle ages.
Someone earlier pointed out the Delhi Pillar as a forge welded object from the 4th century AD, and used it as evidence to show my statement above is incorrect. I just spend a little time looking into this and while they are correct about it's nature, it is not necessarily and good example for this.
It turns out that the iron in that region is special in that it has a naturally high phosphorous content, and the pillar has been tested and shown to be significantly high in phosphorous. High phosphorous- iron alloys melt at much lower temperatures than normal iron, and it can be by as much as 1000 degrees lower. This brings the melting and/welding properties of that iron source into the same temperature range as gold and bronze which is why they could make that pillar at that time. But this has no implications as to the iron found in most of the ancient world which does not contain significant amounts of phosphorous.
This also solves the other mystery of why the pillar does not rust. What scientists have found is that the phosphorous causes the formation of a protective patination which inhibits rusting. This has apparently been known for many years, but but many websites about the pillar still discuss the lack of rust as if it were some big mystery.
Robert Kokotailo
Robert Kokotailo Calgary Coin |
