[TheForge] Iron in the Fire

[xlch58 at swbell.net]

Ben Barrett wrote:
> I'm also thinking
> that the griddles & cast perform via both conduction and convection,
> whereas thinner cookware is almost entirely conduction... somehow it
> seems, that makes a difference.  
No reason for thinner to be by conduction alone, though I expect they 
all use conduction, convection and radiation, with conduction doing the 
lion's share of work.   Heat transfer rate for conduction is a property 
of a number of variables, but in your thick vs thin issue, the one that 
plays the biggest role is the cross sectional area at ninety degrees to 
the path the heat must travel.   A thin griddle will be less able to 
spread heat evenly along the face of the griddle as it has a smaller 
"heat pipe" due to less cross sectional area.   This smaller "heat 
pipe"  will require a bigger temperature gradient to make the heat 
flow.   This is one reason that thicker pieces are less likely to warp, 
they can spread the heat more quickly and evenly.     As a blacksmith 
this should get to be intuitive.  Take a  two foot long 1/4" diameter 
rod and heat the end of it to orange heat, holding the other end in your 
bare hand.  No problem.   No do it with a 1 inch diameter bar.   Or 
switch to aluminum or copper, which have higher thermal conductivity.   

Charles