Low Fire Glazes On High Fire Clay: Hidden Drawbacks?

[parryhotter]

Hi guys,

 

So I made the classic mistake

Of buying cone 06 Duncan Concept underglazes,

Thinking they were cone 6.

 

Painted them on a stoneware

Pot, but thankfully noticed the error,

And fired at cone 06.

 

The result looks OK, but are there

Flaws that will emerge from glazing

Stoneware bodies with earthenware glazes?

 

I know the clay hasn't been fired to its cone 6 maturation temperature, and might not be suitable for outdoor use.

 

I don't have earthenware clay in stock,

And it doesn't really suit my projects (big, slab built pots).

 

Expert guidance appreciated:)

[Min]

A lot of underglazes rated for ^06 can go to ^6. Reds and purples are prone to fading out at ^6 unless they are the ones containing cadmium. Also, you can touch up the underglaze after it has been bisqued with more underglaze.

 

I would do a test piece with all your underglazes on it and fire it to ^6 with an appropriate ^6 glaze and see what they do. You can use underglazes on raw or bisqued clay. Just make sure the underglazes are really dry before you glaze the pots. You can also use them over glazes but then all food safe claims would be off.

 

What clay to use for outdoor use subject to freezing is a whole other topic. Good article here if you are interested http://digitalfire.com/4sight/education/outdoor_weather_resistant_ceramics_105.html

[oldlady]

`actually the mistake you made was in not reading the label.  UNDERglaze means just that, something else should coat the underglaze to make it all permanent.  many of us use underglazes for cone 6 work.  they are a simple way to add a splash of color or some brightness on pieces that are then actually glazed with a cone 6 glaze. (usually clear.)

 

 

these color charts of underglazes show what colors will go to cone 6 and to cone 10.  same underglazes, different firing temps.  some colors fire out at higher heat.  as min suggests, make your own color charts and see what happens.

 

 

.

[parryhotter]

Thanks for the advice, guys:)

 

Nice to see many Duncan brand colours performing well at cones 6 and 10. I will make similar test tiles next chance I get.

 

Heey, I'm not quite THAT dumb yet! Naturally, I used a transparent overglaze on top!

 

Erratum humani est, etc, etc.