3rd firing gives more shrinkage? Controlled cool affect my other glazes?

[Babs]

I have been askedx100 to try to make a replacement lid for a teapot. That specific teapot was fored to cone 5 , clear green glaze,then fired to c 03 which made glaze a microcrustalluzed glaze,"opaque".

Will that 3rd firing cause more shrinkage?

Or if I do a controlled cooldown  what type of glazes may also be altered in that process?  Guy wants it quickly...

I know, I know...

[Bill Kielb]

6 hours ago, Babs said:

That specific teapot was fored to cone 5 , clear green glaze,then fired to c 03 which made glaze a microcrustalluzed glaze,"opaque".

It sounds like the clay was fired to cone 5 and then cone 5 glaze was applied and fired to cone 03 which makes it simply an under fired glaze,  so very matte, but only two glaze firings. Maybe I am reading this incorrectly. If you have a low fire glaze that is matte and very close, or perhaps an acceptable contrast then for the sake of speed,  I think I would make the lid with a relatively broad gallery out of clay you are used to, so easy to fit, fire the clay to cone, then apply the low fire matte glaze and fire to its cone.

I might be misunderstanding though.

[Babs]

33 minutes ago, Bill Kielb said:

It sounds like the clay was fired to cone 5 and then cone 5 glaze was applied and fired to cone 03 which makes it simply an under fired glaze,  so very matte, but only two glaze firings. Maybe I am reading this incorrectly. If you have a low fire glaze that is matte and very close, or perhaps an acceptable contrast then for the sake of speed,  I think I would make the lid with a relatively broad gallery out of clay you are used to, so easy to fit, fire the clay to cone, then apply the low fire matte glaze and fire to its cone.

I might be misunderstanding though.

Sorry, I glazed it fired it to C5, to maturity, then refired to C03 with added oxide brush work. The clear glaze turns "matte". Years ago...

Now I am making 3 lids but only have the measurements of finished pot, photo, pot other side of the country.

Just wondering if there is significant shrinkage occuring at the second glaze firing.  And my other query.

Thanks Bill.

[Bill Kielb]

1 hour ago, Babs said:

Now I am making 3 lids but only have the measurements of finished pot, photo, pot other side of the country.

I don’t think the low fire firing will change it dimensionally a bunch. Can you repeat it but make a generous gallery so it will fit a wider range of opening?

[Babs]

To save time I was going to try a controlled cool of my normal C5 firing . My second question is will this jeopardise the otger glazes in my kiln.

[Min]

17 hours ago, Babs said:

Will that 3rd firing cause more shrinkage?

Nope.

A third firing to ^03 can definitely change the look of glazes fired to mid or high fire. In effect what you would be doing is a strike firing which can alter glazes high in colouring oxides, particularly with iron or copper.

[Babs]

2 hours ago, Min said:

Nope.

A third firing to ^03 can definitely change the look of glazes fired to mid or high fire. In effect what you would be doing is a strike firing which can alter glazes high in colouring oxides, particularly with iron or copper.

Thanks Min , will go with the same procedure as before, drat it!! 

Might unleash a new amazing range though! But ....

It was a copper clear at c5 turning to a "matte" at refire to C03, slip added prior was a copper/ MnO2 thing, only on outside of pot .

 

Edited November 23, 2023 by Babs
Additional info

[Mark C.]

Every firing will weaken the clay after the 1st fire. Can you make the lid and fire it alone-yes it will have an unglazed surface where it sits on shelve but that no big deal