Re: Primaries and Copper Tubing

Subject:        Re: Primaries and Copper Tubing
       Date:    Thu, 24 Apr 1997 17:17:04 +1200
       From:    "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Organization:   Wellington Polytechnic, NZ
         To:    tesla-at-pupman-dot-com

Hi Chris,

>       From:  Chris Gardner <gchristo-at-clt.mindspring-dot-com>
>         To:  Tesla List <tesla-at-pupman-dot-com>

<snip - not too much I hope>
> In blackmithing this is reffered to a the 'critical heat', for iron and
> steel its a mild cherry red, bright enough to be seen in a well lighted
> shop, its around 1400 to 1600 degrees. Ideal annealing is acheived by
> reaching this temp. and placing the item in a trash can filled with
> vermiculite, cooling in this manner can take up to 24 hours based upon
> the mass of the piece.
> I do not know what the crit. heat is for copper, but the controlled
> cooling is just as important as reaching that temp for ideal annealing.

I simply worked my way along the pipe with the torch and let it cool 
naturally. It was a lot quicker than using an oven. I was intrigued 
to hear that you could do it at a much lower temperature. The only 
hassle (not that bad really) was the oxide layer it left which I then 
scraped/flaked off with some reasonably fine emery. I might just give 
the oven idea a run next time I have to do it. 500 degrees F did I