[soyarsm]

I'm new at this. I fired a piece recently and used two different glazes - one says to fire at cone 5/6. The other says to fire at cone 05/06.
the low temperature glaze did OK. The higher temperature glaze seems to have completely disappeared. I would say it was overfired, but the 05/06 glaze did fine. What happened?

If glazes need to fire at different temperatures do you just fire them at different times or can they never be used together on the same piece?

[Mark McCombs]

What cone did you fire the pieces to?

And yes, you would fire them separately as there is a great difference in temperature between cone 05 and cone 6.

You either overfired one of the glazes or underfired the other.

[Diane Puckett]

There are excellent books on glazing and firing. My favorites are John Britt's Complete Guide to High Fire Glazes, Mark Burleson's The Ceramic Glaze Handbook, Robin Hopper's The Ceramic Spectrum, and Hesselberth & Roy's Mastering Cone Six Glazes.

Also check out http://digitalfire.c..._cones_193.html

[Lucille Oka]

soyarsm, on 17 November 2012 - 08:27 AM, said:

I'm new at this. I fired a piece recently and used two different glazes - one says to fire at cone 5/6. The other says to fire at cone 05/06.
the low temperature glaze did OK. The higher temperature glaze seems to have completely disappeared. I would say it was overfired, but the 05/06 glaze did fine. What happened?

If glazes need to fire at different temperatures do you just fire them at different times or can they never be used together on the same piece?

The Cone 05-06 did fine you say and the Cone 5/6 disappeared? It sounds as if you fired low and the high fire glaze is underfired and has changed color only. When firing multiple temperature glazes on one piece, fire the highest temperature glaze first, then apply and fire your lower firing glaze(s). If it were reversed, if you fired high first, the high firing glaze would have been fine and the lower temperature glaze would most likely have bubbles, or may be excessively runny or have some other glaze defect from being overfired.

[Marcia Selsor]

If you wanted to use both glazes on the same piece, you would need to fire the higher temperature glaze (5-6) first. Then apply the lower temperature glaze(05-06) and fire the low temperature.
Marcia

[Ben]

Cones measure heat work. That is not exactly temperature but we simplify it to say that at a given rate of temp climb (say 250f/hour) a given cone will equal a given temperature.
Cones were originally numbered in such a way that they didn't go down to room temperature so they had to go below cone zero. SO, they added a zero to the front of the number and began counting backwards. Therefore, cone 05 is about an equal distance below cone 0 as cone 5 is above.
Do a web search for a cone chart. I have one saved on my computer and several printed out around the studio. You'll be able to see how much difference there is in 05 and 5.

Ben

[soyarsm]

Lucille Oka, on 18 November 2012 - 02:34 AM, said:

soyarsm, on 17 November 2012 - 08:27 AM, said:

I'm new at this. I fired a piece recently and used two different glazes - one says to fire at cone 5/6. The other says to fire at cone 05/06.
the low temperature glaze did OK. The higher temperature glaze seems to have completely disappeared. I would say it was overfired, but the 05/06 glaze did fine. What happened?

If glazes need to fire at different temperatures do you just fire them at different times or can they never be used together on the same piece?

The Cone 05-06 did fine you say and the Cone 5/6 disappeared? It sounds as if you fired low and the high fire glaze is underfired and has changed color only. When firing multiple temperature glazes on one piece, fire the highest temperature glaze first, then apply and fire your lower firing glaze(s). If it were reversed, if you fired high first, the high firing glaze would have been fine and the lower temperature glaze would most likely have bubbles, or may be excessively runny or have some other glaze defect from being overfired.

Thank you so much! Very helpful!