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Glazes firing too dark...different colours


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#1 Nat

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Posted 02 February 2013 - 01:41 PM

Hiya, just looking for a bit of info really...

I bought some stoneware spectrum glazes last week and whilst they've fired lovely, they're not the colours expected at all.

For example, I bought the Lagoon glaze, which is blue and lime green speckled on their example. I fired according to their instructions and mine has come out as a medium brown with very pale blue highlights. Not a trace of lime green to be found, certainly didn't expect any brown.

Another one was the "Textured Cobalt"...not a trace of cobalt or the mustard yellow to be found...instead I got a buff colour with seafoam (very pale green/blue). And another...the Cinnamon Ripple...no trace of white or the cinnamon/wheat colour...instead I have a yellow/orange straw colour base with bits of pink on it.

I fired to cone 5 with a 30 minute hold, medium speed, with kiln lid open a half inch for the first two hours of firing. 11 hours total firing. I have a Paragon Caldera with Sentry Xpress 4 controller.

Any idea where I've gone wrong?

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#2 Karen B

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Posted 02 February 2013 - 04:45 PM

Hiya, just looking for a bit of info really...

I bought some stoneware spectrum glazes last week and whilst they've fired lovely, they're not the colours expected at all.

For example, I bought the Lagoon glaze, which is blue and lime green speckled on their example. I fired according to their instructions and mine has come out as a medium brown with very pale blue highlights. Not a trace of lime green to be found, certainly didn't expect any brown.

Another one was the "Textured Cobalt"...not a trace of cobalt or the mustard yellow to be found...instead I got a buff colour with seafoam (very pale green/blue). And another...the Cinnamon Ripple...no trace of white or the cinnamon/wheat colour...instead I have a yellow/orange straw colour base with bits of pink on it.

I fired to cone 5 with a 30 minute hold, medium speed, with kiln lid open a half inch for the first two hours of firing. 11 hours total firing. I have a Paragon Caldera with Sentry Xpress 4 controller.

Any idea where I've gone wrong?




These are a few things that could cause the difference.


-If these are cone 5 glazes and you hold at the highest temp for 30 mins, this could change the color
as the hold can take the temp up a bit higher.


-The samples you posted appear to be on a white clay. The clay body you use will affect the color.


-The thickness of the application will have a big impact.


-Does the glaze sample say if it is fired in oxidation or reduction?

-Usually this is not an issue with premixed glazes, but worth checking to see if the glaze was mixed well.

If you post pictures of your results, that could help figuring it out.

#3 Chris Campbell

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Posted 02 February 2013 - 04:57 PM

I agree with Karen ..... I would suspect they were over fired ... Cone 5 with a 30 minute hold is probably Cone 6 heading to 7. Always keep in mind that the proper cone is a combination of time and temperature.
Did you have witness cones inside to check on what Cone you reached?

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#4 Iforgot

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Posted 02 February 2013 - 11:24 PM

totally, i would never hold for more than 10 mins for commercial glaze.



Darrel
Derek VonDrehle

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#5 Nat

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Posted 03 February 2013 - 02:53 AM

I used a buff stoneware, will try them on white next with no hold. Have attached some pics...

The leaf (img_4100.jpg) is supposed to be the lime/blue, img_4098 is the textured cobalt and img_4121 is the cinnamon/wheat colour... As you can see, completely different. Thanks for the info, didn't realise the hold would increase the temps so much.

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#6 Chris Campbell

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Posted 03 February 2013 - 11:23 AM

Make notes of what you did to get those colors in case you decide you want them again on some other work. You never know!

Pottery making covers such huge areas of knowledge that it does take years to learn and often we learn from our mistakes .... which I think is a good way to learn as you don't easily forget.

The cone temperatures we use are a combination of time and temperature and both factors have to be taken into account ... so you want the soak to end up at Cone 5 or whatever. I start my soaks at Cone 8 and most of the kiln reaches 9 or 10 ... and I know which areas will have the hotter temps since I always use witness cones on each level. I high fire this way because I have found I get less cracks ... but, this is just what I have found with my clay ... Results will definitely vary.

Witness cones are an inexpensive way to learn your kiln and to monitor each firing. All you need is one power failure to learn that it would have been handy to know exactly how hot the kiln got and if you need to refire.

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#7 bciskepottery

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Posted 03 February 2013 - 11:44 AM

Many glazes will break over texture, during firing the low points get a pool of glaze and the high points get a thinner covering that is often a different color or more of the clay body showing through. Also, the color of your clay will have an influence on the results you get depending on what the glaze maker uses in the glaze and what is in the clay body. Make a couple test tiles, with half the tile smooth surface and half textured . . . then you will have a good reference on what the final results will be on your wares. And, vary the coats on the test tiles, one third -- one brush stroke, one third -- two brush strokes, one third -- three brush strokes; let the tiles dry between brush strokes.

If you like the buff clay for making things, you could put a white slip over the surface for glazing on.



#8 Diane Puckett

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Posted 03 February 2013 - 02:25 PM

Interestingly, Spectrum does show that color bell for Lagoon. However, when I google that glaze for other sites, it consistently comes up showing a light brown sample. I cannot imagine they have two glazes with the same name.
Axner listing for Spectrum Lagoon

I would post a photo but cannot figure out how to do that with my iPad.
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#9 Chantay

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Posted 03 February 2013 - 10:42 PM

How did you apply the glazes? Looks pretty thin. I have had the same commercial glaze look very different depending on the thickness of the application.

-chantay
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