Posts Tagged sparky

Boro colour investigations: NS Aurora

In the GBUK Journal Issue 7 (out April 2015) I had an article showing the results I got from making sets of simple test beads with a range of boro colours from Northstar (NS), Momka, Trautman Art Glass (TAG) and Glass Alchemy (GA). The idea was to give beadmakers new to boro some idea of what the various colours *could* look like, since the paddles aren’t that useful and beads look different from implosions or blown work. There’s still huge variation possible with some colours, but it’s a start!

I work on a Minor and a 10lpm oxycon.

I’m continuing my results here. That article was on beads only, but I’ll be adding implosions, pendants and anything else in here too as I experiment.

First up is a colour that took me a great deal of prodding until I understood how to work it better. I’d read the working notes, then mostly forgotten them when I made the first set of beads.

Northstar Aurora

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These are my first five beads. They all have a clear core. From left to right:
• aurora, encased in clear;
• aurora with clear frit, encased in clear;
• aurora over white, encased in clear;
• aurora over black, encased in clear;
• aurora on surface.

They are mostly brown/tan with a little dull pinky-red and slight hints of purple. On the surface I got the rod colour, which is almost black. They went through my normal kiln schedule which has a striking segment at 621C (1150F) for 10 mins and anneals at 565C (1049F).

They aren’t bad for brown, but I did know aurora was supposed to do more than that. I made a couple more, trying very hard to strike them: still browns.

So I went back to the notes. Northstar newsletter #1 says:

For NS-47 Aurora it is also possible to get a full spectrum of colors depending on which flame is used as well as whether the pieced is encased in clear or a color. To achieve vibrant blues, try working it in a highly oxidizing flame. To yield a green, work it in a neutral flame. To generate vibrant deep reds, work the piece in a neutral flame then reduce the piece when it is close to completion.

(Northstar newsletter #18 mentions using aurora as a backing colour for amber purple and others).

I tried for the high oxy flame. That’s a challenge on oxycons, even a large one, so for a while I wondered if my enough-oxy-to-be-hissing flame wasn’t even neutral, as the more I did, the more my beads remained rod colour.

I turned my oxy up as high as I could get it and the propane down a little for the hissing flame. I made these two beads. To get the lighter areas I had to really blast the surface and then allow to air cool for a long time. I still couldn’t get the whole bead light. The light areas looked greenish before encasing and going in the kiln, but came out like this.

14.12.07_auroratest2

I then made an encased stringer, which looks a dull green with occasional pinker sections (see below). These beads were made with the stringer – the blue stripe on the black bead was where the stringer was encased – I used the end left on the rod, so the black is the unencased glass. The other bead went purplish in the kiln – still very dark.

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I decided to do something a bit bigger next and with no mandrel in the way, so made a pair of scorpion claws.

One claw is solid aurora – still an awful lot of brown-black even for something with a much longer working time that was going in and out of the flame. I used a fairly high oxy flame but also enough propane to let me melt easily. For the second claw, I made a gather of aurora, encased it and then did all the shaping. It looked lighter before it went in the kiln, but came out weirdly salmony with other areas – a few dark blue-purple bits, a little almost-green haze. These were annealed with no striking segment, so at 565C all the way.

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(The natural colour is pretty good for a scorpion).

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This shows the encased stringer too.

Then I found this video clip by Milon Townsend on Firelady’s site, showing that when worked in an oxy flame aurora does indeed remain rod colour! So that was working. He gets a bright red-pink from an entirely reducing flame, no encasing.

I hadn’t been reducing it because
1) I try to work all my first bead sets in roughly the same flame so they can be compared.
2) I was trying for the greens in the Northstar newsletter, which said use a neutral flame. That note leaves out any mention of reducing it after working, apart from getting reds.

For my next beads, I melted my glass entirely in a reducing flame – I got opaque salmony pink showing up on the tip of my rod, which vanished on the bead, but rolling the bead in the edge of the flame made the surface lighten up, and then after encasing it definitely looked different. I also added a new program that doesn’t go above 538C, from a recommendation that it would stop aurora striking browner.

Here is what my rod looked like:

15.01.02_aurora_rod

And this is what I got:

15.01.02_auroratest5

The bead on the left was less reduced than the others and has come out one of those odd in-between colours that I will call taupe. Not very pretty, but different from what I was getting before. I reduced the middle bead enough to get an opaque surface then encased it – I got seagreen along with the salmon pink! The right bead is again reduced a lot, then rolled in clear frit and encased – it has gone purple under the frit and is quite pretty. Progress!

When I say reduced a lot, I had my flame so I just started getting about 2mm of yellow bushy ends on my candles. Get the rod end or bead surface properly hot in this and you’ll see the surface change after a moment or two- that’s when it develops the opaque salmon colour. It’ll tend to go away while forming the bead (even in the same flame) and you’ll have to bring it back again on the surface once you have it shaped.

I went on to make a pair of off-mandrel hearts after that.

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The base is TAG Red Elvis. I added a spiral of aurora round it, added in a reducing flame. In this one I added clear frit when the aurora was still raised, melted it in in a reducing flame, then encased in clear. (I didn’t pull the heart into the best shape here, wasn’t sure which direction to go in!)

15.01.02_auroraheart_v1_02

That’s the other side.

You can see I got a band of green and yellow on one lobe and various other colours, with a good bit of salmon pink and red from the glass that wasn’t under frit. The colour is a little muddy in areas, especially centre back. The area on top of the lobes was added last, worked least, and has the brightest colour. I’ve also got haze spread across the red Elvis areas, which looks pretty cool with the frit on top.

My second heart was a lot bigger. This has a clear core under the red and has a bit of TAG sparky inside too, though you can’t see it much unless you peer (sparky is a dense sparkle – mix it with anything to thin out).

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The aurora was all added to the gather at the same time and melted down fully before the frit was added. I prefer the colours I got the first time as these are more muted. It was also worked longer. The shape is greatly improved though!

15.01.03_auroraheart_v2_02

I went on to make this trio of beads where I tried a lighter hand with the reduction – that didn’t work and I got tiny hints of colour but mostly dark. The little yellow spots are where metals came to the surface. I was trying to brush lightly with the edge of the reducing flame and it really didn’t do much.

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Finally, I made these three.

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From left to right:
1. Formed in neutral flame, heated through in reducing flame once so it went iridescent not opaque, encased. It went a good purple.
2. Reduced a lot, added clear frit, reduced more and encased – I got blue-green and yellow, plus slightly purple round the other side.
3. Reduced a lot, added clear frit, not encased. Red and green, and yellowish round the back, which lost the surface pink.

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That is quite a difference from one glass!

Here are the beads in hand, slightly washed-out, but it shows the yellowy-green back on the last bead.

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Here are the earlier beads together.

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And here ALL the beads!

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I went on to make another large claw.

15.01.04_Aurora_scorpionclaw_01

I encased a gather of clear with aurora, reduced and added the clear frit, reduced again and encased in clear. Then I did the shaping. I got a generally more uniform colour here, mostly pastel mauve though some hints of blue and green also.

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The colour is less eyecatching again, but quite pleasing.

I made a scorpion tail, intended to be brown and black this time!

15.01.01_aurorascorpiontail_01

(This took a long time and is quite fragile because of the nature of the segment joins – I promptly dropped it a short way when taking it out of the kiln, broke it in three and had to fix it. It needs some more construction thought or deliberate smoothing of the segments into each other).

I tried imploding aurora in a jellyfish pendant.

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This came out mostly a warm peachy tan, with hints of all sorts of colours in it. The background is NS blue moon, of which more later.

In conclusion, aurora took quite a lot of work to begin to understand but I do not regret it!

Here are a few posts and pieces by other people I tracked down to give me hope that you could actually get other results from it:

Proof aurora goes green! By Heather/Ericaceae.
Pretty muted multicoloured beads by Suzanne (scroll down).
Darker red/green/blue heart by e. mort.
Brighter blues and greens heart by e. mort.
Discussion of annealing temp to avoid purple aurora going brown (no pics).

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