copper went blue!

[Trudi]

Hi

I'm very new to fusing - but I thought that any copper would turn to red under glass - i made 2 pieces and they both went blue!!


The other one won't show up too well as it's on a black bacground.

While I was expecting red - I really like the blue in this one!! Is there a reason why it's blue? Could it be to do with black??

Thanks

Trudi

[Zeldazog]

Trudi, I sometimes get it red, others that gorgeous greeny, blue, and I have even had a combination.

Not sure why though! 

I don't think its a reaction with the other glass as I have had it occur on same colour but both ways (if you get what I mean - on two same white bases I got two different copper colours come out).

And I can't even say its something to do with hold times, or soak times, but it could be. 

I also wonder if its something to with if oxygen has or hasn't got to the copper before the glass has started to melt, seeing as copper goes green in reduction.  I made a set of six coasters for someone, and she fortunately she didn't mind what colour they came out, so long as they were all the quite similar - the pair she ordered them from were one mainly red and another that had gone half and half!

So I was meticulous in which way I faced the glasses, as most of them have a smoother side, so I made sure they were all the same so they got the same amount of oxygen, in case that is the reason.

This was the first pair that I hadn't been meticulous about, as I didn't know this was going to happen:

You can just see that the top one has more green on one side, the bottom one was all red.  The only explanation I have is the air thing.

Lovely pendant!

[Trudi]

Thanks for that!!

And I really like the cool 2 tone effect on the coasters! I guess that's the beauty of working with glass, you don't always know what you're going to get!

T

[Margram]

That's what I love about the limited amount of fusing I've done - the surprise
element!  I like the bluey-green look that sometimes comes from the copper.
I wonder if it is anything to do with the tin side of the glass, or is that only
with float glass?  Or it could be the heat differences in various parts of the
kiln...or if the copper sheet has been exposed to air for different times... or
if oils from the skin are on there...(or kiln pixies at work  )

Marg x

[Lottie]

I also wonder if its something to with if oxygen has or hasn't got to the copper before the glass has started to melt, seeing as copper goes green in reduction. 

I think you're onto something there.  I was chatting to a lady potter at a craft show the other week,she had some glorious frilly-edged bowls with internal glazes in amazing shades of blue and green. I asked how she'd achieved the colours [being a nosy mare   ] and she told me she chucks copper in the glaze before firing; she let the glaze stand longer for the blue colours and gets the green from 'fresh' glaze.

[Zeldazog]

+I wonder if it is anything to do with the tin side of the glass, or is that only
with float glass? 
Marg x

Only float glass has a tin side, Bullseye doesn't.

[Redhotsal]

Doesn't cooper go green/blue when it's oxidised not reduced? Copper oxide is blue green. Reduced copper is red or, well copper coloured 
Copper roofs go verdigris when they're exposed to the atmosphere (oxidised).
Float glass can have a fine tin layer on the side which is floated on the molten tin when it is formed. Maybe that has some reaction?

[bluefairy]

I know if you put copper under the glass it goes blue ie. it's got more airflow, so it oxidises.  Also, there is a bullseye clear (think it might be crystal clear? but don't quote me) that does react and make the copper go blue, whereas with tekta, if the copper is inside two pieces, it usually (but not always!!) stays red x

Oooh, and they look fab Trudi, I've got some lovely bullseye murrini from lovely Charlotte, that I will get round to trying when i've stopped stroking it 

[Zeldazog]

You can get the blue/green or the deep red with either Bullseye or float glass, so its nothing to do with the tin as far as I can see (or else you wouldn't get the variance in bullseye?) - well, I suppose I can't say that the tin DOESN'T react, but not tinned glass does react either way, as does float glass, so there must be another factor.

I never know which way round it is with reducing copper.  With glazes, I know some ceramists use a gas reduction firing to bring out the strong colours, but I am not very knowledgeable with glaze technology!


Helen, the coasters I did where they went both red and blue/green were done with all Tekta!

I know there is a colour reaction with silver foil turning the normal clear a yellowish colour, so they recommend Crystal clear if using silver wire or foil.

They (bullseye) have recently introduced the reactive glasses, which react with copper based glasses, and possibly foils, but they haven't got much info on them yet.

[Zeldazog]

Just found this....

http://www.susanhutsko.com/inclusions.php

It says:

During the process of firing, copper oxidizes. The areas that oxidize the most turn turquoise, the areas with less oxidation turn red. The oxidation occurs in the kiln in the hours before the glass begins to fuse. Once the edges of the glass have fused, the oxidation process stops.


Sal, you were right.  I am sure some glazes are reduction fired to bring out the blues/greens, so that's probably where I got that from (and I know reds are a bugger to get!)

I might have to experiment with some slooooooooooooow firing schedules, with a long, long bubble soak to see if I can force the blue/green

[Trudi]

well - I did base my firing on Helen P's SC2 schedule - and held for a little longer - extra 5 mins and a tincy bit hotter to allow for the bead door!

[Redhotsal]

Blimey - didn't know we had to be chemists to do this glass malarky! I always remember that metals are "metally looking" and oxides are brightly coloured. If you reduce something you take away it's oxide so reducing is more likely to make something metally looking.

It's a bit simplistic but seems to work for me when trying to remember which way round it is!   

Meant to say - (how rude I am!) that the pendant is really beautiful Trudi!   

[Trudi]

Thanks Sal!

Seems like I sparked off a whole conversation  - amazing stuff this glass!

[Calico Cat]

Love the pendant.

At risk of being a real smart a**e  , there are two oxides of copper :

Cu₂O - in pure form this is red in colour and probabaly responsible for the red colour you would normally expect.

CuO - in pure form this is black in colour but can be used to create red/blue/green - it's the oxide used in ceramic glazes

In theory, the higher the oxygen concentration the more likely you are to get CuO

[Trudi]

Love the pendant.

At risk of being a real smart a**e  , there are two oxides of copper :

Cu₂O - in pure form this is red in colour and probabaly responsible for the red colour you would normally expect.

CuO - in pure form this is black in colour but can be used to create red/blue/green - it's the oxide used in ceramic glazes

In theory, the higher the oxygen concentration the more likely you are to get CuO

you lost me there!