Red on green and vice versa

Those Cu crystals are sharp and delicate. An achievement.
I'm not much for guessing games, but I'll try - looks like a small amount of Cu (maybe .4 gm or so) combined with a very mild reduction -

Arnie

Hi Arnie,the vase about 3 1/2 % CuOx red. Reduced at about 770c with propane, enough propane to get a stream of smoke from the kiln (outside). The dome was placed in granular activated carbon soaked in water. Same temp. No microcrystals Sherri, varying degrees of reduction from contact with the carbon pellets

Hi Gordon - If I use 3.5% CuOx with a 'moderate' reduction I get metallic Cu crystals and ground. For about how many minutes are you in a reduction atmosphere?

I get red crystals on a blue ground with CuCO3 1 CoCO3 .5 Fe2O3 .5 - the ground becomes green if I substitute Ni for the Co - or add 3 or 4 % Ti.

Arnie

was the one on the left etched?

Here are a couple of examples - 

Cu red with blue ground - It's Cu 1 Co .5 Fe 1



Cu red with green ground - Ni 1 Cu1 Fe 1





So the difference is Co makes blue ground and Ni makes green ground.

But it can get much more complicated - here is Ni 2 Cu 1 Fe 2 on top of Fe2 Co .15 Ti 4




And here's a close up of the crystal in the center - 




So the crystals aren't just Cu red, but different colors at different growth temperatures.

I've been thinking about what direction I want to go in, so I'm glad you asked the question. It got me to look back in my notes - and in the process got me thinking more about these multicolored crystals ...

Arnie