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marlies lies

Clear Glaze Recipe For Over Duncan Underglazes

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I have bought some duncan covercoat underglazes and fired some testtiles with 2 types of clear glaze over them, a matte and a glossy.

I make my own glazes and used food-safe cone 6 glazes I have not yet had problems with. 

The colours have dissapeared  and changed after firing.

What is a good recipe for a cone 6 matte - and a cone 6 glossy glaze for over these underglazes?

 

Marlies

 

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Excuse my ignorance but are the Duncan covercoat underglazes rated to go to ^6? I've had problems with violet and purple shades of Spectrum ug's fading to pale blue at ^6. Not sure if that's an issue of too much boron in the clear cover glaze. Without hijacking this thread has anyone had any luck with any of the Spectrum violet/purples at ^6?

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i have had trouble with lots of things in the pink, purple range.  they seem to disappear as the temperature goes higher.  some of the mason stains in purple work, though in some glazes.  i bought a spectrum burgundy glaze years ago.  it came out grey all the time until this year when i actually got burgundy.  i added pansy purple to a matte glaze this summer and it comes out great EXCEPT where the edges are slightly sharp.  that makes the glaze pull away into bubbles that do not flatten out.  have never seen anything like it.

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Thanks for the recipe, Bciskepottery!!! wow, hope it works. :)

The colours I used where lotus yellow, peach and Maroccan red, and the red did indeed turn milky blue.

The others just evaporated.

According to duncan the colours are all tested to 1240 c7 and passed the test. at the test the colours stayed good.

My colours on the not-glazes parts where still great, so the problem must be the glaze.

Does anyone have good results in the red / pink / violet range or did I just pick the most difficult ones again?

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i have had trouble with lots of things in the pink, purple range.  they seem to disappear as the temperature goes higher.  some of the mason stains in purple work, though in some glazes.  i bought a spectrum burgundy glaze years ago.  it came out grey all the time until this year when i actually got burgundy.  i added pansy purple to a matte glaze this summer and it comes out great EXCEPT where the edges are slightly sharp.  that makes the glaze pull away into bubbles that do not flatten out.  have never seen anything like it.

Do you have the purple stain numbers that worked handy?

 

Does anyone have good results in the red / pink / violet range or did I just pick the most difficult ones again?

 

Spectrum Christmas Red and Hot Pink stay the proper intense colours they are supposed to be. I cut the Hot Pink 1:1 with white so it's a softer shell pink. (the pink fluxes at my bisque of 04 and makes it hard to glaze so I only put it on bisque) I use it with a low expansion glaze. 

 

G1215U ^6 

EPK 14.00 

Silica 26.00 

Wollastonite 14.50 

F-4 Feldspar 24.00  (sub Minspar)

Frit 3249 20.00 

98.50

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pansy purple stain seems to have gone walkabout.  and the single sheet with all the colors and numbers on it is somewhere in the big bookcase.  if you are in the USA, call your local supplier and ask or call mason stain.  their tech person it helpful.  there is another purple, deep orchid 6303 which i have used with pansy purple and together they make a great color.  there is a deep crimson 6006 which makes a great color in the cone 6 recipe for Oribe.  usually called oribe green.  just use the base recipe and add 6006 to the right amount, i went %5 and %10 when i tested it.

 

gotta go to a computer lesson, bye!

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I would like to clear up a misconception regarding Mason stains.

They do not disappear in firings all by themselves ... this fade to white is caused by the GLAZE, not the stain.

 

I often bring a wide test tile along to my workshop to show attendees how the colors change from one clear glaze to another.

Glazes with Gerstley Borate turn some greens to brown, certain clear recipes burn out pinks and mauves to whites, others cause the stains to bleed.

Clear glazes are not benign things we put on for shine ... they do other things!

 

If you look at the attached images ... these Mason stained clays were all fired in the Cone 9-10 range and are fine.

The overglaze is a Zinc free Amaco glaze.

post-1585-0-29641100-1415203930_thumb.jpg

post-1585-0-81758700-1415203939_thumb.jpg

post-1585-0-10069400-1415203954_thumb.jpg

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I would like to clear up a misconception regarding Mason stains.

They do not disappear in firings all by themselves ... this fade to white is caused by the GLAZE, not the stain.

 

I often bring a wide test tile along to my workshop to show attendees how the colors change from one clear glaze to another.

Glazes with Gerstley Borate turn some greens to brown, certain clear recipes burn out pinks and mauves to whites, others cause the stains to bleed.

Clear glazes are not benign things we put on for shine ... they do other things!

 

If you look at the attached images ... these Mason stained clays were all fired in the Cone 9-10 range and are fine.

The overglaze is a Zinc free Amaco glaze.

 

I think that is what we were talking about. Boron, calcium, zinc etc having an effect on the colour. Yes, you can get the glaze compatibility info from Mason Stains but with ug's we don't know what stain they have used so matching a correct glaze is a little more work.

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Good point Min ...

I have test tiles of Velvet underglazes showing approximately the same color changes and burn outs as I get with stained clay. Greens going brown, pinks and mauves burning out. I have never used the Duncans so cannot comment there. I don't know about Boron and Calcium, but I have found that eliminating Zinc has been wonderful for my color results.

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Hmm that is a good point, one of the glazes I used did contain zinc. 

I emailed duncan but they replied that they cannot give me advise, was a bit disappointed with that reply because I understood that they have a good advise-board. But the recipes you gave me are a great help, I am going to recalculate them to ingredients I can get here in the Netherlands and see what the difference is with my own standard glazes.

 The not-zinc glaze is a glaze that works great with my pink stain, but not at all with the ug, so that was a surprise. 

I was hoping to find 1 glaze to use over the 3 different colours, because I am still - some years now- trying to get a nice peach-skin colour-effect. The day will be a lucky one when I open the oven and find..... yeah peach!!!

:) 

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