The term "stainless steel" refers to several types of steel that contain small amounts of chromium, which helps the steel resist rusting and corrosion. This property is appealing and useful for both practical and artistic purposes. However, stainless steel is limited in its colour. While it is possible to paint or tint stainless steel, the only ways to permanently alter the colour are through chemical changes or heat. Heat is one of the simpler methods of colouring stainless steel, but it is somewhat dangerous and the results can vary greatly.
Arrange the steel item on a pan or similar flat item that will withstand high heat.
Put the oven thermometer into your oven and turn it on to about 260 degrees Celsius )500 degrees Fahrenheit). When the oven has reached the right temperature, put the pan into the oven. If you are using a kiln, put the pan in before turning on the kiln. A kiln will most likely have a built-in thermometer, so you may not need to put one into the kiln.
Wait. Times will vary depending upon the composition and thickness of the steel. Monitor your steel closely. Turn up the temperature, if necessary, to achieve a true blue colour. Stainless steel turns blue at somewhere between 260 and 316 degrees Celsius (500 and 600 degrees Fahrenheit), so a temperature that is too low may not achieve the colour or shade that you want.
Turn off the oven or kiln when you are satisfied with the colour and wait for the steel to cool completely before handling. Put the steel into a bucket of water to cool it faster, if desired.
If your oven does not reach a high enough temperature, use an oxyacetylene torch. These torches achieve very high temperatures but are dangerous and make an inconsistent effect on the colour of metal, which may or may not be desirable.
Keep a fire extinguisher nearby and work in a well-ventilated area.