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#1 Round2potter

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Posted 01 December 2012 - 04:23 AM

Dear all,

I have been mixing glazes and modifying them for about a year now and i am very curious about the Coinage Metals as colorants. I know that Gold is used in cranberry glass and i have seen glassblowers "gas" a peice with silver for a blue color.

What colors can i get from these metals in feldspathic glazes?

I am more interested in silver as i can get it readily without totally breaking the bank on just a small test batch of glaze.
I have soooo many books on glazes, some new, mostly old classics, and none of them mention these pricey metals in any glazes.

I was going to start with a sodaspar base glaze and a potash base glaze and go from there adding modifiers etc...
What would some good starting %'s be? Do they FLUX like copper does?

Although i test in both electric and gas reduction, i tend to steer towards nicer RDX glazes (copper red, cobalt green, also a darkish iron, groggy body that looks great in RDX)

On a side note i am curious about working with the rare earths, mostly for the fun of showing people glazes glow under UV; has anybody tester gold/silver with Cerium?

Many thanks, hope to hear from ya'll soon

-Burt, Portland Orygun
"There is no such thing as cheating in clay; So long as it works"

#2 Marcia Selsor

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Posted 01 December 2012 - 08:23 AM

when you say coinage metals are you implying you would melt coins?
Amounts of copper in a glaze will vary the color tremendously from red, green blue. It also depends of the base like your soda feldspar.
Sounds like you have a lot more testing to do. I think you need to do more reading on the subject to understand the chemistry going on. If you are working on ^10 you may want to read John Britt's High Fire Glazes or Ian Currie's Revealing Glazes.

Marcia

#3 JBaymore

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Posted 01 December 2012 - 01:23 PM

There is an article in the current issue of Ceramics Monthly on gold as a high fire colorant. Take a look.

I use gold chloride at low temerature (overglaze enamels) for reds. And for gold luster.

Some rare earths are in sonewhat common use. Some more unusual ones have been experimented with a bit. There are older articles in Ceramics Monthly magazine also.

best,

......................john
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#4 Round2potter

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Posted 01 December 2012 - 02:31 PM

Oh i read John Britts book long ago, it is a go to for me when i am doing tests. As for the chemistry, i think i have a good enough grip on it all, i am a super nerdy geochemistry student.

And NO I AM NOT GOING TO MELT COINS, silver carbonate and goldoxides look apealing.

The Coinage Metals is a common name for the column in the periodic table including, copper, silver, gold and roentgenium.

And i am also aware they are used for lusters, but seriousey nobody has used them at stoneware temp?

I guess they will go orange or red, which is what i want.

Are they going to volatize like copper and tin?

Thanks!
"There is no such thing as cheating in clay; So long as it works"

#5 Round2potter

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Posted 01 December 2012 - 02:40 PM

Oh i read John Britts book long ago, it is a go to for me when i am doing tests. As for the chemistry, i think i have a good enough grip on it all, i am a super nerdy geochemistry student.

And NO I AM NOT GOING TO MELT COINS, silver carbonate and goldoxides look apealing.

The Coinage Metals is a common name for the column in the periodic table including, copper, silver, gold and roentgenium.

And i am also aware they are used for lusters, but seriousey nobody has used them at stoneware temp?

I guess they will go orange or red, which is what i want.

Are they going to volatize like copper and tin?

Thanks!
"There is no such thing as cheating in clay; So long as it works"

#6 JBaymore

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Posted 01 December 2012 - 04:02 PM

And i am also aware they are used for lusters, but seriousey nobody has used them at stoneware temp?

I guess they will go orange or red, which is what i want.

Are they going to volatize like copper and tin?


As a chem student... you should likely head over the Digitalfire.com website and see if anything there "floats your boat". One of the best technical resources available for ceramists.

Nope, no volatility to speak of.

The reason that they are not typically used is that they are expensive, and there are cheaper alternatives to produce basically the same kinds of colors.

best,

............john
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#7 bciskepottery

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Posted 01 December 2012 - 05:36 PM

You might want to reach out to Jon Singer -- he's done research into using phosphorous, etc. in glazes. http://71.166.254.21...mics/index.html

#8 Rebel_Rocker

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Posted 01 December 2012 - 05:52 PM

http://www.steveirvi...m/goldleaf.html

he uses gold leaf on pots after fire, you can also get silver leaf. I think that is the best use for them as you actually get the properties that make them so unique. You could also metal turn them, etc... for cool effects. I've also heard about using some gold in the kiln but am not sure what the process is called, it's also used for gold designs like gold leaf, but is suppose to be very tricky to get right, though it might be more permanent for dinner ware.

But like John said, why use gold for reds if you can use copper? I haven't mixed up an glazes personally but i imagine it would take a fair pile of gold powder to get color from it.

#9 Round2potter

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Posted 01 December 2012 - 10:15 PM

Ok Upon looking more into stuff written on glassware/jewelery


Silver should be reddish orange to blue depending on RDX and gold SHOULD be red in both RDX and OX.


I still have no starting percentage, so i will probably do like 1/4%-1% in 1/4% increments. or just start low and see, maybe i wont have to waste any more Au or Ag than needed.

NOW. The real question is what is the best (by best i mean cheapest) form of these metals that i can use.

Thanks all you have been a wealth of places to look.

And in answer to Ag, Au vs. Cu; i love copper, and copper red, i want to see first hand what the others do alone or with Cu (it would at least lessen the cost of a Gold Red.....)
"There is no such thing as cheating in clay; So long as it works"

#10 JBaymore

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Posted 01 December 2012 - 11:07 PM

NOW. The real question is what is the best (by best i mean cheapest) form of these metals that i can use.


Gold chloride is the usual source for gold in ceramic applications. Silver nitrate is the usual choice for that metal.

So.... 1000 grams of glaze does not go very far.

IF....... (making a big assumption here) you get a nice red with a 1% by weight of of gold chloride in the base glaze, that will be 10 grams of gold chloride. 100 ml of gold chloride at only a 1% gold solution costs about $100 and weighs just over 100 grams. So the colorant alone for that 1010 gram batch of red glaze will cost about $10.

For the same 1000 grams of base glaze, in reduction, you can get a nice blood red with no more than about 1% copper carbonate. In the highest price bracket (buyibng a single pound) copper carb costs about $7.00 per pound. So 10 grams of copper carb will cost about $0.15.

best,

..................john
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

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#11 Round2potter

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Posted 01 December 2012 - 11:29 PM

Dear John,

Thanks for the math on that!
although i love to fiddle with glazes, converting % and weight and balancing stuff is a headache for me, not that i cant do it.

I know it is expensive, its gold, i just want to make enough (~50 grams) glaze for test tile or 2. if its 10 bucks for 1 kg it'd be like 50 cents for my tests; i dont know about you but 50 cents seems worth it to me.
I know a science teacher too, so maybe i could buy only a very small amount from the school or through the school too.... we are already talking about making glazes/glass in his freshmen chemistry class this spring (they have a small furnace/kiln).

I dont know of you know many 9th graders, but generally they think anything with gold in it is the bee's knees; a good teaching moment.

Also, i am entertaining the idea of using a raw ore (after ball milling and probably magnetic purification) added to a glaze for color and a source of SiO2

The color and usefulness of the glaze is less important to me than just screwing around with the stuff.

Besides, i would have a glazed tile (red or no red) to show off to fellow glaze test junkies like myself.

Again,

Thanks John!
"There is no such thing as cheating in clay; So long as it works"

#12 Marcia Selsor

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Posted 02 December 2012 - 08:50 AM

Sorry for not being familiar with the term coinage metals...not something I ever heard used before.
It does seem like an extreme measure to use precious metals in this capacity but I understand your effort to engage your students.
Copper in reduction for a red needs about 0.5%
Manganese can give a metallic gold surface in reduction that is very enticing but not what you are looking for.

Good luck and post some results of the tests.

Marcia




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