Topic: "Sori" or Curvature

[Moley]

I was absolutely amazed to learn that the hot metal bends the other way first on quenching and then bends all the way up to create the "Sori" (curvature).
This clip shows the metal being quenched in a see through water trough.
The amount of Sori" is dependent on the claying process.

http://www.youtube.com/watch?v=-4A2JJmWi6Y

[Lloydie]

I guess that the clay first insulates that part of the blade from the cooling process of the water, hence the cooler (outer) part contracts.  Still trying to work out why it then flexs back    does the clay then wash away, exposing the now hotter part which then cools rapidly and causes the second bend?

[Azzy_Stealth]

Just thought about it. 
The blade is made of the same steel.
- unlike a bimetalic thermostat swith made of two metals with different expansion and contraction temperatures.

So the contraction during cooling happens to the blade side first. Which is put in first and is thinner so finishes contracting quickly.
The back of the blade is thicker so it takes longer to contract and therefore bends more over a longer time in the opposite way because the blade side has stopped contracting.

Makes sense to me 
What do you think

[JimmyTheHoover]

Just thought about it. 
The blade is made of the same steel.
- unlike a bimetalic thermostat swith made of two metals with different expansion and contraction temperatures.

So the contraction during cooling happens to the blade side first. Which is put in first and is thinner so finishes contracting quickly.
The back of the blade is thicker so it takes longer to contract and therefore bends more over a longer time in the opposite way because the blade side has stopped contracting.

Makes sense to me 
What do you think

+1 Spot On 

JIm