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kennedy james

is gilding / gold leafing food safe ?

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Tyler Miller    331

I think you might have sailed into some unexplored territory. I have a lustre kicking around, but I've never used it.  Beyond contacting the lustre manufacturer and the glaze manufacturer about what to do, I think experimentation or research might be in order--to me, the best and worst parts of the ceramics game. :)

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Denice    243

Yes it is normal glazes to change when refired to a lower cone, I tested a bunch of formula's from Ceramics Monthly that were meant to be refired.  They were quite ugly at C6 and were beautiful when refired at C04.    Denice

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JBaymore    1,432

I do a lot of china paint and luster work on my woodfired pieces. Yes, they can change ...sometimes a lot (but they all don't).  One of my shinos gets dramatically better.

 

I never try to "burn out" screwed up gold luster. Try to get it 100% before it gets to the kiln. Fix it (if needed) before it is fired. Including total removal (expensive). If it is not something that can be helped by adding a bit more (like a skip) on a refire, I usually just trash the unsucessful piece. Usually... such mistakes repairs show when you try to repair them...... thereby affecting quality.

 

best,

 

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

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jo4550    11

Hello Kennedy

It is normal for some glazes to change on a refire especially when you are approaching the softening point (I do not mean melting point) of the glaze.  This is the point where the fluxes start to be active.   This has become very obvious when running the laser decal classes and searching for the softening point for the decal to adhere.   There is a fine line where the glaze doesn't react and this is at the lower end of the temp scale.   I would hazard a guess that your glaze has a flux that has a very wide firing range and it is perhaps Gerstly Borate.  You seem to have reached a point at cone 06 in your glaze where the glaze is already outgassing and the cooling at 06 halts the process and and traps the gases changing both the colour and the integrity of the glaze.   

 

To resurrect this glaze AND burn off the lustre find a cool spot in your glaze firing and take back up to top temp.   This should restore the glaze.  I say cool spot as refiring is almost like going a cone higher than the original firing.

 

I would have attempted to save the gold and platinum surfaces by adding a couple more layers (with firings in between) and firing to your gold firing temperature before I took the drastic step of burning the lustre off.  To remove small areas of lustre it is common to use a gold eraser but it has to be used carefully as you can "matte" the surface of the glaze that you are rubbing.  Lustre can also be removed by using hydrofluoric acid but I personally wouldn't go down that path for H&S reasons.  It also mattes the surface of the glaze where the lustre has been removed.

 

Cheers

Johanna

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JBaymore    1,432

Kennedy, you just heard from THE person to listen to here when it comes to lusters and overglazes! Check out her work.

 

Johanna...... thanks for sharing your expertise here on the CAD forums.

 

best,

 

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

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I would have attempted to save the gold and platinum surfaces by adding a couple more layers (with firings in between) and firing to your gold firing temperature before I took the drastic step of burning the lustre off.  To remove small areas of lustre it is common to use a gold eraser but it has to be used carefully as you can "matte" the surface of the glaze that you are rubbing.  Lustre can also be removed by using hydrofluoric acid but I personally wouldn't go down that path for H&S reasons.  It also mattes the surface of the glaze where the lustre has been removed.

 

Cheers

Johanna

 

I did add a layer to the silver cup. the cup I try to burn off the luster from was another test, I only wanted to burn it off because some of the luster went on the top where I dont want any... I thought I cleaned everything but the glaze being black it's very hard to see if there is any luster where I don't want it. 

next time I will use a luster eraser if I can find one at my ceramic shop. 

 

thanks for your answers Johanna !

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charad    0

hi.

im a newbie but loving working with gold luster (FYI i was using duncan bright gold till i read johannas recommendation - thanks!)

i have a few purple spots that i need to clean up - how is the best way to go about this.thanks in anticipation

tina

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caseykey    0

I have a piece which has been finished with underglazes and a clear glaze on top, fired to cone 6.  I would like to put some gold on it but have never used any gold in any form.  What would be the best product to use over this combination and would it have to be fired again and at what tempeture?

Thank you for any help.  Caseykey

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