One other thing I would do that I didn't see on the lab sites directions would be to wash the test piece that you are sending in with hot water and soap before sending it off. Have no clue if Cadmium would fume, doubt it though, but remember that thread John B posted from Carty about copper glazed pots leaching far less in the testing if they are washed first. Probably won't make a difference for Cd but not 100% sure.
Can't remember if I have ever mentioned this in THIS thread (not reading back now)... or anywhere here on the CAD forums.........
In Japan, the famous "Oribe" green copper glaze is loaded with copper. One of the standard parts of using that glaze for Japanese potters (that is not all that well known here in the USA) is to take the pieces that are glazed with it and soak them in a solution made from crushed chestnut shells overnight. Basically it is an acid bath. It "clears" the hazy look of the glaze as it comes out of the kiln. It is taking the "loose" copper off the surface and in the immediate surface layer of the fired glaze.
I also note that many "American" versions of "Oribe" greens are so loaded with copper that they cause little black microcrystalline surface silicate precipitations to form. Those areas will be way less stable in holding the copper than fused glassy phase glaze.
The acid soak makes a huge difference in the look of the glaze.
Interesting read John, thanks. I wonder if the tannins from the shells are acting as a mordant in some way also?