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Blue-green / copper red glaze is transparent pale green.


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#1 docweathers

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Posted 07 March 2013 - 12:34 AM

I tried Rick Malmgren's Blue-green / copper red glaze from 15 tried and true cone 6 glaze recipes. I got a shiny transparent glaze with a slight green tint. Has anyone else tried this glaze, with what result? Any clue how to get the beautiful result that Rick displays it in that article?

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#2 esh

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Posted 07 March 2013 - 04:08 AM

I haven't tried this one, but copper red glaze recipe gets red only under reduction. So if you are using an electric kiln, you will not see the nice red of the illustration.
Erez

#3 Brian Reed

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Posted 07 March 2013 - 11:35 AM

Yup esh is right, it would seem you either fired in an electric kiln or used gas and fired in oxidation. To get a red from that copper glaze you must fire in reduction.
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#4 neilestrick

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Posted 07 March 2013 - 11:36 AM

Post the recipe.
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#5 OffCenter

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Posted 07 March 2013 - 12:38 PM

I haven't tried this one, but copper red glaze recipe gets red only under reduction. So if you are using an electric kiln, you will not see the nice red of the illustration.
Erez


Actually, you can get that red in an electric kiln. I have a really nice copper green/red that I sometimes try to fire it so that it is red on the bottom shading into green on the top by firing it in an uncovered sagger with a little coffee grounds in the sagger. Haven't been successful yet in getting that to happen but that's because it comes out red with too little or no green. When I want that glaze to come out red. I fire in a sagger with coffee. Great way to get reduction red in an electric kiln when you don't want to fire up a reduction kiln. As long as you don't overdo it, I think it affects the life of the elements very little.

Jim
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#6 docweathers

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Posted 07 March 2013 - 01:13 PM

Here is the recipe. Note that it says oxidation or reduction. I was firing in a gas kiln under oxidation. For those unfamiliar with it, I have also attached the original document. It really has a lot of nice stuff in it.


Blue-green / copper red
glaze
(Cone 6., oxidation or reduction)
Talc . . . . . . . . . . . . . . . . . . . . . . . . 3 .30 %
Whiting . . . . . . . . . . . . . . . . . . . . .14 .29
Ferro Frit 3134 . . . . . . . . . . . . . . . .13 .33
Kona F-4 Feldspar . . . . . . . . . . . . .46. .16.
EPK Kaolin . . . . . . . . . . . . . . . . . . . 6. .40
Silica . . . . . . . . . . . . . . . . . . . . . . .16. .52
100 .00 %
Add: Tin Oxide . . . . . . . . . . . . . . . . 2 .24 %
Zinc Oxide . . . . . . . . . . . . . . . .4 .37 %
Black Copper Oxide . . . . . . . . .1 .07 %
Covering with clear glaze helps reduce burning
out of red .
From Rick Malmgren,
Ceramics Monthly, October 2000

Attached Files


Larry

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#7 neilestrick

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Posted 07 March 2013 - 01:24 PM

I see nothing in that recipe that would make me think it'll go red in oxidation. I think it's blue/green in oxidation, red in reduction. The saggar trick is worth a try.
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#8 docweathers

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Posted 07 March 2013 - 01:29 PM

Look at the picture in the attached PDF. He is getting both the blue-green and copper red in the same bowl.

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#9 neilestrick

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Posted 07 March 2013 - 01:52 PM

Look at the picture in the attached PDF. He is getting both the blue-green and copper red in the same bowl.


Possibly, or he's used more than one glaze on that bowl. Also, the copper percentage is quite high for a copper red, which is probably contributing to it going blue-green even in reduction. And if you look at his Tenmoku recipe in that list it sounds like he typically fires in reduction.
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#10 docweathers

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Posted 08 March 2013 - 10:41 AM

I emailed Rick Malmgren about this.He states that "It sounds as though you are not getting proper reduction. You need to have the right amount of reduction at the right time in the firing cycle. We go into reduction at cone 010 and maintain it to the end of the firing. You’ll need to experiment with your kiln to get the right results." so the statement in the article that it can be fired "oxidation or reduction" is an accurate.

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#11 OffCenter

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Posted 08 March 2013 - 10:58 AM

I emailed Rick Malmgren about this.He states that "It sounds as though you are not getting proper reduction. You need to have the right amount of reduction at the right time in the firing cycle. We go into reduction at cone 010 and maintain it to the end of the firing. You’ll need to experiment with your kiln to get the right results." so the statement in the article that it can be fired "oxidation or reduction" is an accurate.


I think the statement is accurate. Like many copper red glazes, it can be fired in oxidation to get a green or green-blue glaze that is often as nice or nicer than the red. Obviously, Rick uses the glaze to get a copper red in a reduction firing. As I posted earlier, you can get localized reduction in an electric kiln by using saggers with organic material. So, if you don't have access to a reduction firing you could experiment with saggers. Just in case you're interested, here is a glaze that is a beautiful transparent green in oxidation and a nice red in saggers with coffee grounds or in a reduction firing.

Water Color Green (Cone 6)
Custer ... 47.8
Silica ... 16.9
Lithium Carb ... 4.0
Frit 3124 ... 5.0
Whiting ... 16.0
Strontium Carb ... 7.5
Bentonite ... 2.9
Copper Carb ... 8.0

Jim
E pur si muove.

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#12 docweathers

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Posted 08 March 2013 - 11:04 AM

Thanks for the glaze recipe. I'm using a gas kiln, so I will try it in both oxidation and reduction.

Larry

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#13 neilestrick

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Posted 08 March 2013 - 11:14 AM

Water Color Green (Cone 6)
Custer ... 47.8
Silica ... 16.9
Lithium Carb ... 4.0
Frit 3124 ... 5.0
Whiting ... 16.0
Strontium Carb ... 7.5
Bentonite ... 2.9
Copper Carb ... 8.0

Jim


I've never seen a glaze that can hold more than 5-6% copper carb without leaching, let alone 8%. Have you tested this glaze?

Malmgren should have specified that the red only happens in reduction. It's vague for anyone who's not familiar with the glaze.
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#14 OffCenter

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Posted 08 March 2013 - 11:43 AM


Water Color Green (Cone 6)
Custer ... 47.8
Silica ... 16.9
Lithium Carb ... 4.0
Frit 3124 ... 5.0
Whiting ... 16.0
Strontium Carb ... 7.5
Bentonite ... 2.9
Copper Carb ... 8.0

Jim


I've never seen a glaze that can hold more than 5-6% copper carb without leaching, let alone 8%. Have you tested this glaze?

Malmgren should have specified that the red only happens in reduction. It's vague for anyone who's not familiar with the glaze.


Yes, it does leach. Not as badly as you might expect but there is some leaching. I don't use it where it would come into contact with food. Thanks for pointing this out. I should have done so when I posted the recipe.

Jim
E pur si muove.

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#15 Marcia Selsor

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Posted 08 March 2013 - 11:51 AM

Here is the link to Rick Mailgram's article making the switch from ^10 reduction to ^6 reduction. I think he was very clear about it being for reduction.
http://ceramicartsda...leap-to-cone-6/

Marcia

#16 neilestrick

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Posted 08 March 2013 - 12:23 PM

OP got the recipe from the 16 Tried and True Glazes publication, which did not contain all the information in that article.
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#17 Marcia Selsor

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Posted 10 March 2013 - 07:55 AM

Yes, sometimes crucial information is left out of the edited down versions of articles from publications. I have had that experience with my own articles reposted in CAD.

Marcia




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