[TheForge] Putting an oxide finish on mild steel?

[Gladish Family]

I get a very nice version of this color when I forge ladles out of pure 
iron, wire brush, and bake them when the kids make a pizza, with a 
little olive oil on them.
I don't know if it's really consistent enough for a production piece...
Andy g.

Steve Smith wrote:

>
>
> Aaron Stavens wrote:
>
>> I had another different piece of sheet steel I had welded on with E6013.
>> I had baked it in my kitchen oven and, unintentionally, it acquired a
>> dark blue color with purple and copper highlights. There is also a nice
>> iridescence in places. My friend saw this and liked it. So, I'm trying
>> to achieve a similar effect on the bracket.
>>
>> I figured I would buff the bracket with a wire wheel and bake it in the
>> oven like I did with the previous piece. The baking didn't go so well.
>> All I could achieve was a very light translucent blue even after hours
>> in the oven. I assume my oven simply isn't hot enough, but I'm already
>> running it at the maximum of 550F. I also tried heating the bracket with
>> my welding torch. I achieved a whole rainbow of colors, but I couldn't
>> seem to control the colors I achieved.
>
>
> You're right in describing this as an oxide finish. What happens is if 
> you have a thin enough layer of oxide, light hitting the surface will 
> interfere with itself (this thin the oxide is essentially 
> transparent). This reinforces some wavelengths and reduces others, 
> which leads to colors.
>
> I think what you have might be too thick a layer of oxide, giving you 
> the translucent blue. Try running it at several lower temperatures 
> (400F? 450F?) and see what happens. Make up some test pieces and take 
> them out of the oven at different times.
>
> You might also try heating one end of a shiny piece of metal with a 
> torch. The colors "run" along the rest of the piece really quickly 
> when you get to the right temperature. It may be tricky to control, 
> even in an oven.
>
> Steve
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