Clear Glaze Recipe

[Katrien]

Hi,

can anyone give me a good recipe for a completely clear glaze for stoneware high temperature (1200 °C). It's to use over other colors of glaze, engobes... to protected drawings but one that does not alter the colors to much. The gloss one we currently use at the artschool makes pink clay look grey! after firing at high temperature.

 

I'm looking for a gloss and a matted version.

 

Thanks!

[Mudlark]

Your query raises a lot of questions as it is unlikely that a true clear glaze will have a great influence on the colour of the clay. Are there any additives in the glaze recipe that can cause a colour cast? You can have a clear, that is a transparent glaze, which is coloured by additives or contamination of the materials used in it's composition e.g. small amounts of iron.

 

What type of kiln are you using, the kiln atmosphere can influence the colour of the fired clay. Have you fired a sample of the clay without a glaze on it, this will help decide the cause of the final colour as it will eliminate the effects of the glaze. A quick way to check is to look at the unglazed foot ring but this is not a definitive check as the ring is in close contact with the kiln shelf which isolates it to some extent from the gasses in the chamber.

 

Is the clay that you are using recycled from scrap? If so you may need to consider "contamination" from a mixture of clay bodies each of which will contribute to the final colour when fired. If you want a pristine white background you may need to change your clay and keep it isolated from any recycling that takes place.

Mudlark

[Marcia Selsor]

Is the pink clay pink due to adding mason stains? If so, refer to the reference guide to see if the pink stain should not be used with zinc or of it prefers calcium..whatever. Follow the directions.

You can find clear glaze recipes all over the place. google it...but find what you need. You haven't provided enough information for us to help.

[Guest Jessica Knapp]

Hi Katrien,

I think this might be what you're experiencing. When a stoneware is bisque fired, it is pink. When it is high fired in a reduction atmosphere (in a gas kiln where the environment inside the kiln is starved of oxygen) many light colored or buff stoneware clay bodies will come out as a gray color with darker speckles under a clear glaze and a brown to brownish gray on unglazed areas. In an oxidation atmosphere (plenty of oxygen present) the clay will be a buff color, and look yellowish under a clear glaze. It really depends on your clay.

 

If I'm right in guessing that the pink color you see is at the bisque stage when you're applying glaze, and that you're firing the work in a gas kiln, the solution might not lie in getting a different glaze. It might be to simply use a white slip on your clay, covering the entire piece with it when it is leather hard, then after the first (bisque) firing, you can glaze it with the shop clear/ gloss glaze. If you want the clay to look pink, you could add mason stains to the slip. Do tests as some colors burn out at mid to high fire ranges.

Hi,

can anyone give me a good recipe for a completely clear glaze for stoneware high temperature (1200 °C). It's to use over other colors of glaze, engobes... to protected drawings but one that does not alter the colors to much. The gloss one we currently use at the artschool makes pink clay look grey! after firing at high temperature.

 

I'm looking for a gloss and a matted version.

 

Thanks!