Hi...I do a lot of different arting, and only recently got to playing with enamels.
I'm fascinated by the colors I can get with transparent flux,
and now found out that an opaque white will surprize me with colors in a similar way. 
I've gotten such varied results color wise, that I think these two enamels will keep me fascinated for a long time.
I would love to know if anyone knows how to get these unique variations on a more regular basis.
I'm not concerned with total control.
I like the surprize, and the natural way the colors develop.
I'm getting everything! Reds, yellows, pinks, greens, limes, burgandys...some blues,
or maybe that's just burned out green- but it's fabulous. They sparkle!
I wish I knew how to take better photos of them...shiney things stump me.
  I'm anxious to order some opaque white. My torch is a $2.99 propane torch from Menards. 

Hi Linda,

What your witnessing is the copper oxides interacting with the white opaque enamels. Same with the flux, altho, with the flux,  once the copper oxides have been completely absorbed into the enamel, you will have a golden color as if you used gold foil.

Hello Linda

Trish has pointed to the phenomena of copper oxides migrating into the enamel and effecting colour change. I would add that the degree of colour variation depends on thickness of the white layer; a thick layer tends to be more stable. In my experience the main factor governing the hue, is temperature and time. At high temperature the white will become more transparent. Refire at a lower temperature and the true colour is partially restored.

Whether you get purples, blues, greens or pinks will depend on temperature, time, and how many refires you give it. If you use a kiln and set some control over these parameters you will begin to see this. But as you are using a torch then you will see the entire gamut of colour as you play around with the flame and adjust the torch. The gas and oxygen mix will also have an effect  - I imagine.

Firing high and then low, repeatedly, sometimes makes the whites become opalescent. That can be lovely.

Dirty, or greasy copper, will vary the oxide response and give colour variation. I quite like old and grubby copper for that reason.

Anyway, best wishes.

Harry

I'd forgotten to mention that you will get different results by trying a range of fluxes and whites - they differ according to manufacturers' mix of doping minerals. The softest (lowest melting point) enamels are more amenable. Try some with lead content also - if you can find them (they are still used in Europe).

Here is a Fred Ball technique, described on pages 118-119 of his out-of-print book.  Using Thompson's leaded Soft White (no longer available) or Bovano (Soyer) leaded 160 White [per Sandra Kravitz] you can fire to bring out strong blues, pinks, greens, and purple-gold.  Is that enough color for you?

Here's the torch firing technique: Sift the enamel directly onto copper foil which has not been counter-enameled.  Heat gently from below until fused.  Then bring the torch very close below the copper and watch while the colors develop.  Variations depend on length of time and intensity of heat.