Help Annealing Aurora and Multicolor

[stuwaudby]

I've been getting really frustrated this week. After getting wonderful colours and effects after working I find that both Northstar Aurora and Multicolor turn to a dark muddy brown after annealing. I am annealing at 570 Celcius, The Northstar manual states 566. It also says that both colours can handle alot of heat! The pieces are simple frilled discs wrapped in clear and melted to round.

Anyone else had this or got a solution?

[garishglobes]

It does sound as if they are overstriking when annealed, if the colours are there before they go in the kiln. I anneal at 565C, but unless your kiln is overshooting or misreading the temperature, I wouldn't have thought 570 would make enough difference to dramatically change the colours.
You could try using vermiculite/annealing bubbles following working, to check that the colours are there when the piece has cooled, and checking the flame atmosphere (both will turn to mud in a reducing flame) but if the colours are there when the beads have cooled and are not there when you have batch annealed, then I'd be a bit stumped. You could try annealing at 565 

[stuwaudby]

I give the beads about a minute to air cool below glowing before they go in the bead cube. The colours are great when they go in the Kiln and are encased so atmosphere/flame has nothing to do with it. Do you use multi / aurora?

[garishglobes]

I've used Dark Multi a bit, and Aurora on occasion. I find Aurora quite stiff and bubbly so tend to avoid it on the whole, but it has given me some nice effects with Amber Purple on the top.

Flame atmosphere could still be playing a part before encasing, might be worth a quick check - and colours can change as the bead cools. I'd be tempted to use vermiculite to cool a bead or two, check the colours when cool and then again after annealing. At least that would isolate the kiln as the problem.

[stuwaudby]

Dropped the temp to 555 last night and still got brown beads out. Interestingly I did a test bead with a white core, followed by multi then clear. The multi in that is hardly visible, just faint lines of green. Wonder of the chemistry of the bead release / mandrel is causing the problem...

[garishglobes]

Aurora by A flame with desire, on Flickr

This is a core of Aurora with a few small dots of amber purple swirled in. I cooled and reduced the aurora a bit to get that lovely rainbow sheen (which to be honest would be my preferred look for this glass - unencased and rainbowy). I then encased and added flowers.
The colours are probably more intensely blue/green in real life, with some purple and a slight sheen under the clear. The core behind the blues and greens is brown, but then, Aurora is brown and to my mind the colours only come out to play on the surface, so this is what I'd expect.