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claclana

most iridiscent effect

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Some glass and glass tiles can be dichromatic which is really iridescent-I’m not able to recall that process for glass-not ceramic-I once knew it-(old brain)

 

In ceramics I can say that mother of pearl luster can be near what you are looking for though its not as snappy.

 

Luster like gold /silver/platinum/mother of pearl are cone 017 and cone 018

 

Very nasty/toxic off gassing occurs with these and precautions on application and fumes need to be addressed. I have not smelled luster’s in 25years but can still bring the exact smell up in my brain. If you want to simulate a migraine smell luster’s.

 

Hopefully some luster experts will chime in on this. I still have all above-mentioned lusters –I feel they are best left in the bottles along with the headache.

 

If your kiln is outside and or well vented and you wear an appropriate vapor mask and gloves your will be good to go.

 

Mark

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YES!!

thanks for your data!!

Mark, I have noticed the lusters but didn't know about their toxicity and smell (and their pricesunsure.gif) thanks!

 

Marcia: fume with flame work / torch? like silver fume, but fuming what?...or how? huh.gif

 

Am I correct in assuming that high silica glaze with titanium dioxide, plus CuO can be the solution!? (or I am building a bomb here!!?)(I imagine that the black slip is to show off the iridescence even further, or does some contribution?)

THANKS!!!biggrin.giftongue.giftongue.gifsmile.gif

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but fuming what?...or how

You can fume a load of pots as it cools down around dull red heat-I have done this with the salt kiln a few times -results vary all over the load some are super some are muddy-some really bad.

again this a toxic process with things like stannous chloride and other nasty stuff its expensive and if you want more control stick to luster's

Mark

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fwiw titanium dioxide encourages an iridescent effect - although more towards a pearl type opalescence.

 

I was looking for a pearl type glaze, Glaze Mixer has "mother of pearl":

 

http://www.glazemixe...er%20of%20Pearl

 

Some potters say it's nothing but white, then others are talking about layering with Magic Strontium

I thought, would be nice to mix my own. Slurrious , do you have a particular recipe for pearl glaze cone 5-6 you can share?

Same question to Neil about high silica glaze for iridescent-like effect, your sharing will be greatly appreciated.

Thanks, Lena

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YES!!

thanks for your data!!

Mark, I have noticed the lusters but didn't know about their toxicity and smell (and their pricesunsure.gif) thanks!

 

Marcia: fume with flame work / torch? like silver fume, but fuming what?...or how? huh.gif

 

Am I correct in assuming that high silica glaze with titanium dioxide, plus CuO can be the solution!? (or I am building a bomb here!!?)(I imagine that the black slip is to show off the iridescence even further, or does some contribution?)

THANKS!!!biggrin.giftongue.giftongue.gifsmile.gif

bismuth subnitrate and silver nitrate . This type of fuming is done inside the kiln. It is

 

 

Process of introducing metallic salts into kiln or onto wares at about cone 018, producing thin layer of metallic surface iridescence. from CAD

 

Marcia

 

 

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For rainbow luster I have sprayed Stannous chloride onto crackle white glaze after firing and before reducing a raku. For gold luster I have used ferric chloride the same way.

Fir irridescent fuming of a salt kiln I have waved a metal can of stannous chloride in the kiln after salting. It looks like carnival glass which I didn't like.

Marcia

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Guest JBaymore

Remember that the results of in-kiln fuming work are very much a mega-thin layer sitting on the very surface of the ware. That surface is very prone to damage and wear. So this is not for "functional" work (as in food service and the like).

 

If you want something a bit more durable (but still not bulletproof) look into true Persian Luster glazes. They contain reducible metals and the kiln is fired in a soot producing level of reduction on the cooling phase until below color. Everything is covered in soot when you remove it from the firing. Then you clean it up and "poof" there are stunning lusters. Requires not only a fuel burning kiln, but a place where you can make carbon SMOKE without "issues".

 

For the easiest approach, use commercial liquid lusters. Toxic to use and fumes from kiln are bad, but they work, are reliable, and produce a decent surface (again not highly durable). You trade off $$$$ in buying them for the "it works" factor.

 

best,

 

.....................john

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Remember that the results of in-kiln fuming work are very much a mega-thin layer sitting on the very surface of the ware. That surface is very prone to damage and wear. So this is not for "functional" work (as in food service and the like).

 

If you want something a bit more durable (but still not bulletproof) look into true Persian Luster glazes. They contain reducible metals and the kiln is fired in a soot producing level of reduction on the cooling phase until below color. Everything is covered in soot when you remove it from the firing. Then you clean it up and "poof" there are stunning lusters. Requires not only a fuel burning kiln, but a place where you can make carbon SMOKE without "issues".

 

For the easiest approach, use commercial liquid lusters. Toxic to use and fumes from kiln are bad, but they work, are reliable, and produce a decent surface (again not highly durable). You trade off $$ in buying them for the "it works" factor.

 

best,

 

.....................john

 

They are fabulous for effect, but ooooh boy do they stink when applying and firing them!

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"...do you have a particular recipe for pearl glaze cone 5-6 you can share?"

 

the only one i know is fired to ^8-9 in oxidation and uses volcanic ash. the glaze enjoys the cooler spots in the kiln and i know volcanic ash can sometimes be substituted for feldspar and silica so i can offer a starting point of sorts.

 

feldspar 42

silica 18

whiting 23

Boraq 10

titanium dioxide 6

tin oxide 0.5

 

the Boraq is a gerstley borate substitue http://digitalfire.c.../boraq_124.html

 

i've since added more silica to prevent some crazing. the last batch i mixed up had 10% added but i do know i've lost the opalescence with added silica approaching 15% iirc.

 

where thinner this glaze produces a nice opal effect. where thicker it's white with a subtle opal sheen. there are occasionally some small clusters of tiny blisters that aren't really much of an issue except to annoy me. the claybody is a plainsman 550 http://plainsmanclay...m/data/H550.HTM

 

this glaze was a bit of an obsession for longer than i care to admit and i can understand why some people might want to keep their recipe close. but i feel it is my duty to pass this harlot of a glaze off on someone else. so if you find yourself a year from now still chasing an opal/Chun/Jun glaze take heart - there have been a few before you. http://www.jonsinger.../rutilejun.html

 

*i forgot to add 1-2% light magnesium carbonate or some other suspension agent

 

Dear Slurrious, thank you for your reply and the recipe. The Blues on the last link look absolutely beautiful!

Is there a way to adjust this recipe to cone 6? Or the whole point of getting effect is to fire high?

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ya i found myself at Jon Singer's site more than a few times wishing i could find something near as nice.

 

i've never tried to lower the firing range of a glaze but a few things come to mind. The whiting(high temperature flux) can be reduced by 15% or so. in the original recipe whiting is added to the boraq to make boraq3 which is recommended for higher temperatures.

 

boron(flux) is another option. adding boron in the form of boraq will lower the firing range but adds silica so you might consider reducing the silica as well. you might want to reduce the silica anyway.

 

i know the glaze melts well at an 8 but changing from volcanic ash to feldspar and silica will change things a bit. if i were trying to test this glaze at a 6 i think i'd mix three. one as is, one with 15% less whiting and one with ? 5% more boraq and 3% less silica and less whiting. i suppose ideally a person would change one thing at a time and see how it affects the melt and colour but that's only the ideal. :)

 

another thought - zinc oxide plays well with tin and titanium. i can't remember what amounts i tried or what the result but zinc oxide is very active flux in low amounts so another test with 1-2% zinc oxide might be fun. crystal glazes have a lot of zinc with titanium so there is definitely something along this line.

 

anyway

 

it's fun trying to think through a glaze - hope this helps

 

*the zinc thing got me wondering - turns out i never tested small amounts of zinc on it's own. it was always with dolomite or wollastonite.

 

:huh:<_<;):)

If you come to NCECA, you should try to meet Jon. He carries his latest glaze tests with him. He is a very serious glaze guru.

Marcia

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Guest JBaymore

it's as good of an excuse as any to fiddle with a glaze.

 

Ahhhh...... beware the Dark Side. cool.gif

 

best,

 

...............john

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YES!!

thanks for your data!!

Mark, I have noticed the lusters but didn't know about their toxicity and smell (and their pricesunsure.gif) thanks!

 

Marcia: fume with flame work / torch? like silver fume, but fuming what?...or how? huh.gif

 

Am I correct in assuming that high silica glaze with titanium dioxide, plus CuO can be the solution!? (or I am building a bomb here!!?)(I imagine that the black slip is to show off the iridescence even further, or does some contribution?)

THANKS!!!biggrin.giftongue.giftongue.gifsmile.gif

 

google Biz Littell Vapor Fuming

Below is from Gary ferguson's Raku Newsletter.

 

 

* Glazing *

 

Vapor Glazing

 

There was a question emailed to me after last month's issue as to "What is Vapor Glazing."

 

So I did a little research and discovered an old issue of Clay Times - March/April 2001 that had an article covering Vapor Glazing by Biz Littell. His technique is named "Kosai ware" which means "hue of light" and involves the use of precious metals such as gold and platinum or special salts such as Stannous Chloride.

 

His process is to first bisque fire the piece, then glaze fire the piece to cone 04. Then the piece is fired a third time to about 1000F at which point the kiln is opened to cool down to about 800F. One to two tablespoons of stannous chloride crystals are quickly poured on the hot kiln shelf around the pieces (but not on the pieces). Then the kiln is closed for a few minutes to give the salts time to fume the pieces.

 

This colorant effect is more permanent that the standard Raku copper matte flashing effect.

 

These chemicals are apparently very corrosive so it is critical that the proper safety equipment is used - respirator, mask, gloves, etc.

 

 

 

 

 

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As I read all your writings, it brought back to mind my university instructor, John Takehara. He did a remarkable series of pots (bowls bottles, jugs, tea service) wherein he used lusters. Started with gold and silver, but the silver tarnished to quickly. Switched over to platinum and added gold leaf to many. If he worked on the pots at school, he wouldn't allow anyone else in the studio. He was good about making sure no one would suffer from the ill effects of these metallics--except himself.

 

H would work--hunched over pot after pot--for hours, and never wore any type of respirator. After several years, friends and associates noticed that his memory was rapidly failing. When he finally passed, it was attributed to Alzhiemer's with damage also to his respiratory system. The potter's world lost a true master of the craft because the respirator interfered with his view (he wore glasses) and became too much trouble. His exposure was not for a prolonged time--maybe 3-6 years--and he went downhill rapidly.

 

Any of you who use ferric chloride (and it's cousins) or any lusters--be careful out there!

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