Deleted
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Post by Deleted on Nov 29, 2016 11:59:57 GMT -6
If anyone has experienced this problem, or has an idea of its cause, I would certainly like to know. In the images below, in both vases, I used identical clay bodies, identical glazes with identical thickness of application. Both were fired together for the glaze firing. What turned the right one smoky (along with others) was a second firing to apply the gold. It seems somewhat of a stretch to think that something in the gold resin, of which there was but a small amount, caused the entire vase to turn dark, especially when I've fired gold on vessels with the same glaze and they came out fine, perhaps with a very slight tinge of smokiness. And with different glazes there was no effect whatever. The glaze components are: Ferro Frit 3110...........................48.4% Calcined Zinc Oxide.....................24.35 Calcined Kaolin.............................1.52 Flint..........................................17.95 Titanium Dioxide..........................7.78 Colorants: Copper carbonate..........3.5 Cobalt carbonate..........................0.3  |
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BillC
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Post by BillC on Nov 29, 2016 12:48:40 GMT -6
Did you crack the lid to allow the kiln to breathe? It probably is from the smoke from your luster.
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Deleted
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Post by Deleted on Nov 29, 2016 12:53:04 GMT -6
I had half the peep plugs removed, but it's hard for me to imagine that the tiny bit of gold I have on the piece would smoke the entire vase, especially in such an even way from top to bottom on both pieces. But you may be right. I suppose I can fire it all off, gold and smoke, smoke and try again.
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Post by jfox on Nov 29, 2016 14:34:15 GMT -6
may be the effect of "striking"refiring the piece to 1300 to 1500 can have major effect on colors there are many threads on it maybe Arnie will chime in He's the strike master
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Post by mohawkpiper on Nov 29, 2016 14:45:14 GMT -6
striking is what it is with the copper being your biggest culprit and the titanium a maybe second.
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Post by mohawkpiper on Nov 29, 2016 14:46:48 GMT -6
burning the gold off will only darken the glaze
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Deleted
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Post by Deleted on Nov 29, 2016 16:23:39 GMT -6
Thank you for the responses.
I only took it to cone 019 (1250F) but that seems to be the only explanation. Part of the mystery is why others, with exactly the same glaze formula, didn't do that in other gold firings.
I don't think the piece is bad. In fact I rather like the effect, but it was more or less the wild card of not knowing what the exact cause was.
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Post by mohawkpiper on Nov 29, 2016 21:41:19 GMT -6
i think because you are right on the edge of when it starts happening. copper likes it a little hotter. maybe for whatever reason that one was just a little easier or hotter in the strike. you can fire your gold on to cone 018 and still have the gold work (you might get a little matte ish with it occasionally tho) and possible get the striking effect more often but to really make sure it will work go to 017 or 016 with copper glazes.
different glazes do different things at different temps but i think generally copper gets darker the higher you go until a certain point.
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Deleted
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Post by Deleted on Nov 29, 2016 21:51:22 GMT -6
What you said, Greg, makes a lot of sense. I fired the gold on this one a little cooler, to 019, to try to avoid the issue. In a previous firing, I got a bit of matte when firing to 018, just as you suggested might happen.
Just for clarification, are you suggesting firing the gold on at 017 or 016 to avoid this effect, or to replicate it?
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Post by mohawkpiper on Nov 30, 2016 2:39:34 GMT -6
i guess i was talking about two different things. the gold luster (if its the same one i have) should be fired from 020 to 019. 018 works too but it starts to get matte. i havent fired gold luster hotter but im guessing you dont want to take it to 017 or even 016. I dont know what cone they suggest to fire it off but its obviously hotter than 018.
The striking effect of the glaze changing colors i think barely starts to happen at 019 for some glazes and not consistently. Go a little higher and the results are more consistent. for me with my copper glazes i get a pretty dark drastic change somewhere around 017 or 016.
so i guess i am saying if u want to avoid the smoky effect try firing your luster closer to 020. if you want to replicate it more consistently and still have the luster fire closer to 018. if u arent using the luster and want the smoky effect try firing to cone 017 or 016.
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Post by mohawkpiper on Nov 30, 2016 2:52:00 GMT -6
here is the only example on the web that i have before  after  |
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Deleted
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Post by Deleted on Nov 30, 2016 10:40:48 GMT -6
I get it. I've been using both Duncan liquid bright gold and Alexandar's, which recommend 019 to018. On these I did 019, so my next try will be 020. Those photos give a clear illustration of what you are describing, Greg. Thank you.
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Deleted
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Post by Deleted on Nov 30, 2016 11:28:33 GMT -6
Do you think using a dilute acid bath would alter the surface substantially?
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Post by mohawkpiper on Nov 30, 2016 15:41:55 GMT -6
i havent done the acid thing yet. i guess that is more picky on the thickness of the glaze. maybe it would.
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annie
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Post by annie on Dec 2, 2016 11:19:54 GMT -6
Gabriel,
I really like the one you say is smokey! But bung it in some acid and see what happens after some hours.
--Annie
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