304 Stainless Steel heat coloring inconsistencies

Q. I have a .4mm thick and 29mm diameter piece of 304 stainless steel. One side was polished to 8k and had a protective film on it. The other side did not.

I removed the protective film and cleaned with acetone and hot soapy water.

I place my steel on an electric burner. The coil on it was red hot indicating it was well beyond the 1,000 °F-ish temp needed to turn the steel blue.

I laid my steel on the coil and let it set. When I quenced it the polished side I had cleaned was kind of a chocolatey brown color. The unpolished side which I didn't really bother to clean became purple with splotches of blue.

Why would I get 2 different colors on the thin steel? 1 side is 1 color, 1 side is a different color?

I know since I didn't get blue it tells me I didn't get my disc hot enough.

Q. I should add too, is it possible to get an even consistent color on 304 stainless steel? I am wanting a dark blue. As I tinker more I get the colors but they are splotchy. I have used a kiln set to 1,100 °F, I tried a butane torch with the piece resting on a thin piece of steel with copper shavings, and the electric burner coil.

Thanks so much for the tip. Is there a good resource to read up on to learn how to do this?

Ed. note: You can search the site for 'coloring of stainless steel' for a good start.