Copper Heat Treatment: Fixing Orange/Brown Patina & Preserving Vibrant Colors

Question
I heat treated a piece of copper and got a great pink and purple color.  however when i sealed the patina it turned orange and brown.  I was told to use an clear enamal spray.  can i do anything to change it back to the bright colors i had before?  and if not is there any way to keep those bright colors in the next piece i make?

Answer
Hello Rebekah,
The best thing to do  with copper is to  make some test tiles.The trick  is noting the flame size and  the  length of time  using  x  grade of copper  and at which gauge.  You will find it hard to recreate the same colour again and again as  ambient temperature and other factors, humidity, pre-preparation etc. all influence the outcome. Also  the  way you direct the flame  which gas is used and the surface on which  you are heat treating it, (as opposed to using a controlled  environment in a  furnace or kiln) all affect the  outcome, and  ability to recreate the process.
As for sealing the piece,  enamel is  best if against the skin. Otherwise a micro crystalline wax sealant is best  for preserving the colours you get. I know it is  wondrous to see  different colours revealed in the  heating of a metal , but  getting the same thing to happen twice is  happenstance without some real work!
Pinks and purples are - from  different times and  different heat concentrations on the piece.  I'm betting the pink was furthest away from the purple  which is probably where the flame was.. If you  look into some older metallurgy  books they will help explain the colours possible with varying temperatures. I hope this is  enough to  begin your experimentation with, if not   feel free to write back and I'll go into the  science involved a bit further.
Best regards,Ari