Just thinking out loud here, but from the initial description of "...using brass chips..." in the pan I'm wondering if the OP isn't asking about a pan for heat bluing, not chemical bluing. ie: the pan is heated, the part nestled on the chips (more like dust, really), and the chips conduct the heat evenly through the part resulting in a blue oxide layer. Often used with light-weight things like clock hands. Similar technique is employed for browning edges of wood veneer for those sunburst-type of inlay patterns except using a pan of sand as the heat conducting material.
-frank