The only way I know of to blacken stainless steel is to send it to a company for a black oxide coating, i.e. bluing. There are four classes of black oxide/blue:
Class 1: Alkaline oxidizing. For wrought iron, cast and malleable irons, common carbon, and low alloy steels.
Class 2: Alkaline oxidizing. Use on certain corrosion resistant steel alloys tempered at less than 900°F.
Class 3: Fused salt oxidizing. For corrosion resistant steel alloys which are tempered at 900°F (482°C) or higher.
Class 4: Alkaline oxidizing. For other corrosion resistant steel alloys.
I copied this information from www.techplate.com, the URL for their black oxide info page is here:
[url]http://www.techplate.com/black_oxide_coating.htm[/url]
Techplate, or any other finishing company, should be able to put a black oxide finish on your stainless.
Or, if you're set up to do hot bluing (with all the hardware required), you can get the chemicals from Brownells:
[url]http://www.brownells.com/aspx/NS/Store/ProductDetail.aspx?p=1103[/url]