Cone 05 Glaze in a Cone 04 Firing

[KatzPots]

Please note that my subject line is incorrect - not a Cone 04 firing but a Cone 06 firing:

I am about to fire a Cone 06 load using a commercial clear glaze. I fire Fast in an electric kiln and so the final temperature runs to the high end of Cone 06.

 

 

I am curious - if I were to apply an Amaco Cone 05 glaze to a piece and then add a coat of the Cone 06 Clear glaze to the piece, does anyone have an idea what might happen? I have a practice piece that I could experiment with but was looking for some feedback before I do something foolish.

 

More specifically, will the lower temperature glaze help the higher temperature glaze to melt?

[Slipaholic]

I’d fire iton top of a bisque disk or stilt just to be on the safe side, and place it inthe middle part of the kiln as the top and bottom usually cool faster.

 

 

How thick youapply the layer of the glazes also will affect the outcome, not only the meltbut the color as well.

 

 

A shinny cone05 glaze might fire “ok†(in appearance), be satin or just plain unfired/crustylooking at cone 06. The three worstthings that could happen is that the interaction between the glazes makes itrun, bubble or not get enough heat work to properly melt the glazes.

 

 

On the otherhand a satin cone 06 glaze might stay the same (in appearance), turn bit or alot more glossy, run a bit or quite a bit at cone 04.

 

 

Amaco makesmany different types of glazes… I tried Amaco glazes some years ago. From whatI remember the LG and F series, benefit from the higher cone firing and theopalescent ones look flat if fastfire and some of them can be runny if applied thick.Then again this is all a matter of personal taste.

 

 

There aremany variables… not only the cone and final temp. The fact that you are firingcone 06 on the sitter/computer doesn’t mean that every part of the kiln reachescone 06. A fast fired cone 06 might not even properly mature the cone 06 glazesyou are using. Some glazes melt better with a higher temperature other needtime to mature or develop visual texture. Final temperature or more time might alsomake the glaze run, depending on the composition.

 

 

A thing thatyou’re not asking but that you should take into account if the work isutilitarian (food safe), is whether your fast fire program needs some tweaking(ramping/soaking/slow cooling) to avoid crazing. Crazing is not something youcan sometimes see readily, but might be there. To check you can try using somesafe fine powder like corn starch. Sprinkle it and the rub/brush it away… Withearthenware the crazing is sometimes delayed, so the glaze might look ok afterfiring and two weeks later be crazed.

 

 

Many peoplefire commercial glazes higher to get a different effect. I have a friend who fastfires commercial glazes to cone 02… I regularly fire the few commercial glazesI use to cone 04/03 on the sitter. If the work doesn’t need to be food safe youdon’t have to worry as much…

 

 

It takes timeto get to know glazes. Only by experimenting you’ll find what works for you, butI also suggest you read some on the science behind it so it’s not only fun butsafe as well.

 

[KatzPots]

To follow up, I ran the experiment yesterday. I applied the Cone 05 glaze and followed with the Cone 06 Clear Glaze and placed the piece on a bisque disc in case of running.

I fired to Cone 06 fast to a temperature of 1855. Inspecting the piece today, it looks good and the glazes melted and fused well. Some nice mottling of the glaze. No crazing. No running.

 

Thanks to Slipaholic for all the information you provided. I appreciate your time.

 

 

[Pres]

To follow up, I ran the experiment yesterday. I applied the Cone 05 glaze and followed with the Cone 06 Clear Glaze and placed the piece on a bisque disc in case of running.

I fired to Cone 06 fast to a temperature of 1855. Inspecting the piece today, it looks good and the glazes melted and fused well. Some nice mottling of the glaze. No crazing. No running.

 

Thanks to Slipaholic for all the information you provided. I appreciate your time.

 

 

 

 

I used Amaco glazes for years in HS with the kids, and a lot of their glazes were marked cone 05-06. The difference is not really great, and we ran to 06 in an electric kiln, and I mixed different ranges of pots all of the time. Biggest concern was to make certain a 1/4 inch was bare on the sides and bottom was clean. We taught the kids to do a beveled undercut on all pottery not on feet, even the handbuilt. This helped a lot.

[KatzPots]

Thanks Prez. Your experience is exactly the feedback that I was looking for.

I probably could have placed the Cone 05 glaze piece in the Cone 06 firing without adding the Cone 06 glaze over it.

I included a close up of the experimental piece and there was nice mottling on the rim and in the deeper cuts.

 

[Pres]

Thanks Prez. Your experience is exactly the feedback that I was looking for.

I probably could have placed the Cone 05 glaze piece in the Cone 06 firing without adding the Cone 06 glaze over it.

I included a close up of the experimental piece and there was nice mottling on the rim and in the deeper cuts.

 

 

 

Nice effect, breaking over your textures. This sort of thing happens often with combinations of Amaco glazes, the problem is experimenting enough to know which glazes to use. One of the benefits of teaching for years is that you get to choose the glazes, and then watch the kids try and combine them in all sorts of weird ways. If they kept good records, and you paid attention the future kids got great guidance from you. One of the reasons I insisted that people mark down what they used where. . . .didn't always happen but. . .. .they were kids.