Hi there I will tell you of an incident that happened to me.
I made an 18ct/ diamond belly button ball closure ring for a
solicitor (lawyer). Cleaned it the usual way (ultrasonic). Sent
it down to the body
piercer ready for the client. The Piercer Auto claved the ring
in a steri le bag. When the ring came out ,it had turned purple.
All hell broke loose. I really did not feel that it should be
used for the clients piercing as I did not know what had
happened. The very next day I took the ring to the Sheffield
Assay office. They ran some tests for me (that should of cost
upward of A31000).
The Assay told me that it was top quality 18ct with negligable
cadmium ( less than background). The auto-clave works at about 130
degrees C. To this day I do not know ho w it happened. Maybe some
finger grease my have reacted with the gold and oxidised it. The
purple surface just wiped off after I had it tested. When I have
the time I intend to experiment with the colouring of gold as
the colour was so vibrant. If anyone else has experienced this or
has any info please let me know.